%% =====================================================================
%% Licensed under the Apache License, Version 2.0 (the "License"); you may
%% not use this file except in compliance with the License. You may obtain
%% a copy of the License at <http://www.apache.org/licenses/LICENSE-2.0>
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% Alternatively, you may use this file under the terms of the GNU Lesser
%% General Public License (the "LGPL") as published by the Free Software
%% Foundation; either version 2.1, or (at your option) any later version.
%% If you wish to allow use of your version of this file only under the
%% terms of the LGPL, you should delete the provisions above and replace
%% them with the notice and other provisions required by the LGPL; see
%% <http://www.gnu.org/licenses/>. If you do not delete the provisions
%% above, a recipient may use your version of this file under the terms of
%% either the Apache License or the LGPL.
%%
%% @copyright 1997-2006 Richard Carlsson
%% @author Richard Carlsson <carlsson.richard@gmail.com>
%% @end
%% =====================================================================

%% @doc Support library for abstract Erlang syntax trees.
%%
%% This module contains utility functions for working with the
%% abstract data type defined in the module {@link erl_syntax}.
%%

-module(erl_syntax_lib).
-moduledoc """
Support library for abstract Erlang syntax trees.

This module contains utility functions for working with the abstract data type
defined in the module `m:erl_syntax`.
""".

-export([analyze_application/1, analyze_attribute/1,
         analyze_export_attribute/1, analyze_file_attribute/1,
         analyze_form/1, analyze_forms/1, analyze_function/1,
         analyze_function_name/1, analyze_implicit_fun/1,
         analyze_import_attribute/1, analyze_module_attribute/1,
         analyze_record_attribute/1, analyze_record_expr/1,
         analyze_record_field/1, analyze_wild_attribute/1, annotate_bindings/1,
         analyze_type_application/1, analyze_type_name/1,
         annotate_bindings/2, fold/3, fold_subtrees/3, foldl_listlist/3,
         function_name_expansions/1, is_fail_expr/1, limit/2, limit/3,
         map/2, map_subtrees/2, mapfold/3, mapfold_subtrees/3,
         mapfoldl_listlist/3, new_variable_name/1, new_variable_name/2,
         new_variable_names/2, new_variable_names/3, strip_comments/1,
         to_comment/1, to_comment/2, to_comment/3, variables/1]).

-export_type([info_pair/0]).

%% =====================================================================
%% @type syntaxTree() = erl_syntax:syntaxTree(). An abstract syntax
%% tree. See the {@link erl_syntax} module for details.
-type syntaxTree() :: erl_syntax:syntaxTree().

%% =====================================================================
%% @spec map(Function, Tree::syntaxTree()) -> syntaxTree()
%%
%%          Function = (syntaxTree()) -> syntaxTree()
%% 
%% @doc Applies a function to each node of a syntax tree. The result of
%% each application replaces the corresponding original node. The order
%% of traversal is bottom-up.
%%
%% @see map_subtrees/2

-doc """
Applies a function to each node of a syntax tree. The result of each application
replaces the corresponding original node. The order of traversal is bottom-up.

_See also: _`map_subtrees/2`.
""".
-spec map(fun((syntaxTree()) -> syntaxTree()),
	  syntaxTree()) -> syntaxTree().

map(F, Tree) ->
    case erl_syntax:subtrees(Tree) of
        [] ->
            F(Tree);
        Gs ->
            Tree1 = erl_syntax:make_tree(erl_syntax:type(Tree),
                                         [[map(F, T) || T <- G]
                                          || G <- Gs]),
            F(erl_syntax:copy_attrs(Tree, Tree1))
    end.


%% =====================================================================
%% @spec map_subtrees(Function, syntaxTree()) -> syntaxTree()
%%
%%          Function = (Tree) -> Tree1
%%         
%% @doc Applies a function to each immediate subtree of a syntax tree.
%% The result of each application replaces the corresponding original
%% node.
%%
%% @see map/2

-doc """
Applies a function to each immediate subtree of a syntax tree. The result of
each application replaces the corresponding original node.

_See also: _`map/2`.
""".
-spec map_subtrees(fun((syntaxTree()) -> syntaxTree()),
		   syntaxTree()) -> syntaxTree().

map_subtrees(F, Tree) ->
    case erl_syntax:subtrees(Tree) of
        [] ->
            Tree;
        Gs ->
            Tree1 = erl_syntax:make_tree(erl_syntax:type(Tree),
                                         [[F(T) || T <- G] || G <- Gs]),
            erl_syntax:copy_attrs(Tree, Tree1)
    end.


%% =====================================================================
%% @spec fold(Function, Start::term(), Tree::syntaxTree()) -> term()
%%
%%          Function = (syntaxTree(), term()) -> term()
%%
%% @doc Folds a function over all nodes of a syntax tree. The result is
%% the value of `Function(X1, Function(X2, ... Function(Xn, Start)
%% ... ))', where `[X1, X2, ..., Xn]' are the nodes of
%% `Tree' in a post-order traversal.
%%
%% @see fold_subtrees/3
%% @see foldl_listlist/3

-doc """
Folds a function over all nodes of a syntax tree. The result is the value of
`Function(X1, Function(X2, ... Function(Xn, Start) ... ))`, where
`[X1, X2, ..., Xn]` are the nodes of `Tree` in a post-order traversal.

_See also: _`fold_subtrees/3`, `foldl_listlist/3`.
""".
-spec fold(fun((syntaxTree(), term()) -> term()),
	   term(), syntaxTree()) -> term().

fold(F, S, Tree) ->
    case erl_syntax:subtrees(Tree) of
        [] ->
            F(Tree, S);
        Gs ->
            F(Tree, fold_1(F, S, Gs))
    end.

fold_1(F, S, [L | Ls]) ->
    fold_1(F, fold_2(F, S, L), Ls);
fold_1(_, S, []) ->
    S.

fold_2(F, S, [T | Ts]) ->
    fold_2(F, fold(F, S, T), Ts);
fold_2(_, S, []) ->
    S.


%% =====================================================================
%% @spec fold_subtrees(Function, Start::term(), Tree::syntaxTree()) ->
%%           term()
%%
%%          Function = (syntaxTree(), term()) -> term()
%%
%% @doc Folds a function over the immediate subtrees of a syntax tree.
%% This is similar to `fold/3', but only on the immediate
%% subtrees of `Tree', in left-to-right order; it does not
%% include the root node of `Tree'.
%%
%% @see fold/3

-doc """
Folds a function over the immediate subtrees of a syntax tree. This is similar
to [`fold/3`](`fold/3`), but only on the immediate subtrees of `Tree`, in
left-to-right order; it does not include the root node of `Tree`.

_See also: _`fold/3`.
""".
-spec fold_subtrees(fun((syntaxTree(), term()) -> term()),
		    term(), syntaxTree()) -> term().

fold_subtrees(F, S, Tree) ->
    foldl_listlist(F, S, erl_syntax:subtrees(Tree)).


%% =====================================================================
%% @spec foldl_listlist(Function, Start::term(), [[term()]]) -> term()
%%
%%          Function = (term(), term()) -> term()
%%
%% @doc Like `lists:foldl/3', but over a list of lists.
%%
%% @see fold/3
%% @see //stdlib/lists:foldl/3

-doc """
Like `lists:foldl/3`, but over a list of lists.

_See also: _[//stdlib/lists:foldl/3](`lists:foldl/3`), `fold/3`.
""".
-spec foldl_listlist(fun((term(), term()) -> term()),
		     term(), [[term()]]) -> term().

foldl_listlist(F, S, [L | Ls]) ->
    foldl_listlist(F, foldl(F, S, L), Ls);
foldl_listlist(_, S, []) ->
    S.

foldl(F, S, [T | Ts]) ->
    foldl(F, F(T, S), Ts);
foldl(_, S, []) ->
    S.


%% =====================================================================
%% @spec mapfold(Function, Start::term(), Tree::syntaxTree()) ->
%%           {syntaxTree(), term()}
%%
%%          Function = (syntaxTree(), term()) -> {syntaxTree(), term()}
%%
%% @doc Combines map and fold in a single operation. This is similar to
%% `map/2', but also propagates an extra value from each
%% application of the `Function' to the next, while doing a
%% post-order traversal of the tree like `fold/3'. The value
%% `Start' is passed to the first function application, and
%% the final result is the result of the last application.
%%
%% @see map/2
%% @see fold/3

-doc """
Combines map and fold in a single operation. This is similar to
[`map/2`](`map/2`), but also propagates an extra value from each application of
the `Function` to the next, while doing a post-order traversal of the tree like
[`fold/3`](`fold/3`). The value `Start` is passed to the first function
application, and the final result is the result of the last application.

_See also: _`fold/3`, `map/2`.
""".
-spec mapfold(fun((syntaxTree(), term()) -> {syntaxTree(), term()}),
	      term(), syntaxTree()) -> {syntaxTree(), term()}.

mapfold(F, S, Tree) ->
    case erl_syntax:subtrees(Tree) of
        [] ->
            F(Tree, S);
        Gs ->
            {Gs1, S1} = mapfold_1(F, S, Gs),
            Tree1 = erl_syntax:make_tree(erl_syntax:type(Tree), Gs1),
            F(erl_syntax:copy_attrs(Tree, Tree1), S1)
    end.

mapfold_1(F, S, [L | Ls]) ->
    {L1, S1} = mapfold_2(F, S, L),
    {Ls1, S2} = mapfold_1(F, S1, Ls),
    {[L1 | Ls1], S2};
mapfold_1(_, S, []) ->
    {[], S}.

mapfold_2(F, S, [T | Ts]) ->
    {T1, S1} = mapfold(F, S, T),
    {Ts1, S2} = mapfold_2(F, S1, Ts),
    {[T1 | Ts1], S2};
mapfold_2(_, S, []) ->
    {[], S}.


%% =====================================================================
%% @spec mapfold_subtrees(Function, Start::term(),
%%                        Tree::syntaxTree()) -> {syntaxTree(), term()}
%%
%%          Function = (syntaxTree(), term()) -> {syntaxTree(), term()}
%%
%% @doc Does a mapfold operation over the immediate subtrees of a syntax
%% tree. This is similar to `mapfold/3', but only on the
%% immediate subtrees of `Tree', in left-to-right order; it
%% does not include the root node of `Tree'.
%%
%% @see mapfold/3

-doc """
Does a mapfold operation over the immediate subtrees of a syntax tree. This is
similar to [`mapfold/3`](`mapfold/3`), but only on the immediate subtrees of
`Tree`, in left-to-right order; it does not include the root node of `Tree`.

_See also: _`mapfold/3`.
""".
-spec mapfold_subtrees(fun((syntaxTree(), term()) ->
			      {syntaxTree(), term()}),
		       term(), syntaxTree()) ->
        {syntaxTree(), term()}.

mapfold_subtrees(F, S, Tree) ->
    case erl_syntax:subtrees(Tree) of
        [] ->
            {Tree, S};
        Gs ->
            {Gs1, S1} = mapfoldl_listlist(F, S, Gs),
            Tree1 = erl_syntax:make_tree(erl_syntax:type(Tree), Gs1),
            {erl_syntax:copy_attrs(Tree, Tree1), S1}
    end.


%% =====================================================================
%% @spec mapfoldl_listlist(Function, State, [[term()]]) ->
%%           {[[term()]], term()}
%%
%%          Function = (term(), term()) -> {term(), term()}
%%
%% @doc Like `lists:mapfoldl/3', but over a list of lists.
%% The list of lists in the result has the same structure as the given
%% list of lists.

-doc """
Like `lists:mapfoldl/3`, but over a list of lists. The list of lists in the
result has the same structure as the given list of lists.
""".
-spec mapfoldl_listlist(fun((term(), term()) -> {term(), term()}),
			term(), [[term()]]) -> {[[term()]], term()}.

mapfoldl_listlist(F, S, [L | Ls]) ->
    {L1, S1} = mapfoldl(F, S, L),
    {Ls1, S2} = mapfoldl_listlist(F, S1, Ls),
    {[L1 | Ls1], S2};
mapfoldl_listlist(_, S, []) ->
    {[], S}.

mapfoldl(F, S, [L | Ls]) ->
    {L1, S1} = F(L, S),
    {Ls1, S2} = mapfoldl(F, S1, Ls),
    {[L1 | Ls1], S2};
mapfoldl(_, S, []) ->
    {[], S}.

%% =====================================================================
%% @type set(T) = //stdlib/sets:set(T)
-type set(T) :: sets:set(T).

%% =====================================================================
%% @spec variables(syntaxTree()) -> set(atom())
%%
%%
%% @doc Returns the names of variables occurring in a syntax tree, The
%% result is a set of variable names represented by atoms. Macro names
%% are not included.
%%
%% @see //stdlib/sets

-doc """
Returns the names of variables occurring in a syntax tree, The result is a set
of variable names represented by atoms. Macro names are not included.

_See also: _[//stdlib/sets](`m:sets`).
""".
-spec variables(syntaxTree()) -> set(atom()).

variables(Tree) ->
    variables(Tree, sets:new()).

variables(T, S) ->
    case erl_syntax:type(T) of
	variable ->
	    sets:add_element(erl_syntax:variable_name(T), S);
	macro ->
	    %% macro names are ignored, even if represented by variables
	    case erl_syntax:macro_arguments(T) of
		none -> S;
		As ->
		    variables_2(As, S)
	    end;
	_ ->
	    case erl_syntax:subtrees(T) of
		[] ->
		    S;
		Gs ->
		    variables_1(Gs, S)
	    end
    end.

variables_1([L | Ls], S) ->
    variables_1(Ls, variables_2(L, S));
variables_1([], S) ->
    S.

variables_2([T | Ts], S) ->
    variables_2(Ts, variables(T, S));
variables_2([], S) ->
    S.


-define(MINIMUM_RANGE, 100).
-define(START_RANGE_FACTOR, 100).
-define(MAX_RETRIES, 3).    % retries before enlarging range
-define(ENLARGE_ENUM, 8).   % range enlargement enumerator
-define(ENLARGE_DENOM, 1).  % range enlargement denominator

default_variable_name(N) ->
    list_to_atom("V" ++ integer_to_list(N)).

%% =====================================================================
%% @spec new_variable_name(Used::set(atom())) -> atom()
%%
%% @doc Returns an atom which is not already in the set `Used'. This is
%% equivalent to `new_variable_name(Function, Used)', where `Function'
%% maps a given integer `N' to the atom whose name consists of "`V'"
%% followed by the numeral for `N'.
%%
%% @see new_variable_name/2

-doc """
Returns an atom which is not already in the set `Used`. This is equivalent to
[`new_variable_name(Function, Used)`](`new_variable_name/2`), where `Function`
maps a given integer `N` to the atom whose name consists of "`V`" followed by
the numeral for `N`.

_See also: _`new_variable_name/2`.
""".
-spec new_variable_name(set(atom())) -> atom().

new_variable_name(S) ->
    new_variable_name(fun default_variable_name/1, S).

%% =====================================================================
%% @spec new_variable_name(Function, Used::set(atom())) -> atom()
%%
%%          Function = (integer()) -> atom()
%%
%% @doc Returns a user-named atom which is not already in the set
%% `Used'. The atom is generated by applying the given
%% `Function' to a generated integer. Integers are generated
%% using an algorithm which tries to keep the names randomly distributed
%% within a reasonably small range relative to the number of elements in
%% the set.
%%
%% This function uses the module `rand' to generate new
%% keys. The seed it uses may be initialized by calling
%% `rand:seed/1' or `rand:seed/2' before this
%% function is first called.
%%
%% @see new_variable_name/1
%% @see //stdlib/sets
%% @see //stdlib/random

-doc """
Returns a user-named atom which is not already in the set `Used`. The atom is
generated by applying the given `Function` to a generated integer. Integers are
generated using an algorithm which tries to keep the names randomly distributed
within a reasonably small range relative to the number of elements in the set.

This function uses the module `rand` to generate new keys. The seed it uses may
be initialized by calling `rand:seed/1` or `rand:seed/2` before this function is
first called.

_See also: _[//stdlib/random](`m:random`), [//stdlib/sets](`m:sets`),
`new_variable_name/1`.
""".
-spec new_variable_name(fun((integer()) -> atom()), set(atom())) -> atom().

new_variable_name(F, S) ->
    R = start_range(S),
    new_variable_name(R, F, S).

new_variable_name(R, F, S) ->
    new_variable_name(generate(R, R), R, 0, F, S).

new_variable_name(N, R, T, F, S) when T < ?MAX_RETRIES ->
    A = F(N),
    case sets:is_element(A, S) of
        true ->
            new_variable_name(generate(N, R), R, T + 1, F, S);
        false ->
            A
    end;
new_variable_name(N, R, _T, F, S) ->
    %% Too many retries - enlarge the range and start over.
    R1 = (R * ?ENLARGE_ENUM) div ?ENLARGE_DENOM,
    new_variable_name(generate(N, R1), R1, 0, F, S).

%% Note that we assume that it is very cheap to take the size of
%% the given set. This should be valid for the stdlib
%% implementation of `sets'.

start_range(S) ->
    erlang:max(sets:size(S) * ?START_RANGE_FACTOR, ?MINIMUM_RANGE).

%% The previous number might or might not be used to compute the
%% next number to be tried. It is currently not used.
%%
%% It is important that this function does not generate values in
%% order, but (pseudo-)randomly distributed over the range.

generate(_Key, Range) ->
    _ = case rand:export_seed() of
	    undefined ->
		rand:seed(exsplus, {753,8,73});
	    _ ->
		ok
	end,
    rand:uniform(Range).			% works well


%% =====================================================================
%% @spec new_variable_names(N::integer(), Used::set(atom())) -> [atom()]
%%
%% @doc Like `new_variable_name/1', but generates a list of
%% `N' new names.
%% 
%% @see new_variable_name/1

-doc """
Like [`new_variable_name/1`](`new_variable_name/1`), but generates a list of `N`
new names.

_See also: _`new_variable_name/1`.
""".
-spec new_variable_names(integer(), set(atom())) -> [atom()].

new_variable_names(N, S) ->
    new_variable_names(N, fun default_variable_name/1, S).

%% =====================================================================
%% @spec new_variable_names(N::integer(), Function,
%%                          Used::set(atom())) -> [atom()]
%%
%%          Function = (integer()) -> atom()
%%
%% @doc Like `new_variable_name/2', but generates a list of
%% `N' new names.
%% 
%% @see new_variable_name/2

-doc """
Like [`new_variable_name/2`](`new_variable_name/2`), but generates a list of `N`
new names.

_See also: _`new_variable_name/2`.
""".
-spec new_variable_names(integer(), fun((integer()) -> atom()), set(atom())) ->
	[atom()].

new_variable_names(N, F, S) when is_integer(N) ->
    R = start_range(S),
    new_variable_names(N, [], R, F, S).

new_variable_names(N, Names, R, F, S) when N > 0 ->
    Name = new_variable_name(R, F, S),
    S1 = sets:add_element(Name, S),
    new_variable_names(N - 1, [Name | Names], R, F, S1);
new_variable_names(0, Names, _, _, _) ->
    Names.

%% @type ordset(T) = //stdlib/ordsets:ordset(T)
-type ordset(T) :: ordsets:ordset(T).

%% =====================================================================
%% @spec annotate_bindings(Tree::syntaxTree(),
%%                         Bindings::ordset(atom())) -> syntaxTree()
%%
%% @doc Adds or updates annotations on nodes in a syntax tree.
%% `Bindings' specifies the set of bound variables in the
%% environment of the top level node. The following annotations are
%% affected:
%% <ul>
%%     <li>`{env, Vars}', representing the input environment
%%     of the subtree.</li>
%%
%%     <li>`{bound, Vars}', representing the variables that
%%     are bound in the subtree.</li>
%%
%%     <li>`{free, Vars}', representing the free variables in
%%     the subtree.</li>
%% </ul>
%% `Bindings' and `Vars' are ordered-set lists
%% (cf. module `ordsets') of atoms representing variable
%% names.
%%
%% @see annotate_bindings/1
%% @see //stdlib/ordsets

-doc """
Adds or updates annotations on nodes in a syntax tree. `Bindings` specifies the
set of bound variables in the environment of the top level node. The following
annotations are affected:

- `{env, Vars}`, representing the input environment of the subtree.
- `{bound, Vars}`, representing the variables that are bound in the subtree.
- `{free, Vars}`, representing the free variables in the subtree.

`Bindings` and `Vars` are ordered-set lists (cf. module `ordsets`) of atoms
representing variable names.

_See also: _[//stdlib/ordsets](`m:ordsets`), `annotate_bindings/1`.
""".
-spec annotate_bindings(syntaxTree(), ordset(atom())) ->
        syntaxTree().

annotate_bindings(Tree, Env) ->
    {Tree1, _, _} = vann(Tree, Env),
    Tree1.

%% =====================================================================
%% @spec annotate_bindings(Tree::syntaxTree()) -> syntaxTree()
%%
%% @doc Adds or updates annotations on nodes in a syntax tree.
%% Equivalent to `annotate_bindings(Tree, Bindings)' where
%% the top-level environment `Bindings' is taken from the
%% annotation `{env, Bindings}' on the root node of
%% `Tree'. An exception is thrown if no such annotation
%% should exist.
%%
%% @see annotate_bindings/2

-doc """
Adds or updates annotations on nodes in a syntax tree. Equivalent to
[`annotate_bindings(Tree, Bindings)`](`annotate_bindings/2`) where the top-level
environment `Bindings` is taken from the annotation `{env, Bindings}` on the
root node of `Tree`. An exception is thrown if no such annotation should exist.

_See also: _`annotate_bindings/2`.
""".
-spec annotate_bindings(syntaxTree()) -> syntaxTree().

annotate_bindings(Tree) ->
    As = erl_syntax:get_ann(Tree),
    case lists:keyfind(env, 1, As) of
        {env, InVars} ->
            annotate_bindings(Tree, InVars);
        _ ->
            erlang:error(badarg)
    end.

vann(Tree, Env) ->
    case erl_syntax:type(Tree) of
        variable ->
            %% Variable use
            Bound = [],
            Free = [erl_syntax:variable_name(Tree)],
            {ann_bindings(Tree, Env, Bound, Free), Bound, Free};
        match_expr ->
            vann_match_expr(Tree, Env);
        case_expr ->
            vann_case_expr(Tree, Env);
        if_expr ->
            vann_if_expr(Tree, Env);
        receive_expr ->
            vann_receive_expr(Tree, Env);
        catch_expr ->
            vann_catch_expr(Tree, Env);
        try_expr ->
            vann_try_expr(Tree, Env);
        function ->
            vann_function(Tree, Env);
        fun_expr ->
            vann_fun_expr(Tree, Env);
        named_fun_expr ->
            vann_named_fun_expr(Tree, Env);
        list_comp ->
            vann_list_comp(Tree, Env);
        binary_comp ->
            vann_binary_comp(Tree, Env);
        generator ->
            vann_generator(Tree, Env);
        binary_generator ->
            vann_binary_generator(Tree, Env);
        block_expr ->
            vann_block_expr(Tree, Env);
        macro ->
            vann_macro(Tree, Env);
        _Type ->
            F = vann_list_join(Env),
            {Tree1, {Bound, Free}} = mapfold_subtrees(F, {[], []},
                                                      Tree),
            {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}
    end.

vann_list_join(Env) ->
    fun (T, {Bound, Free}) ->
            {T1, Bound1, Free1} = vann(T, Env),
            {T1, {ordsets:union(Bound, Bound1),
                  ordsets:union(Free, Free1)}}
    end.

vann_list(Ts, Env) ->
    lists:mapfoldl(vann_list_join(Env), {[], []}, Ts).

vann_function(Tree, Env) ->
    Cs = erl_syntax:function_clauses(Tree),
    {Cs1, {_, Free}} = vann_clauses(Cs, Env),
    N = erl_syntax:function_name(Tree),
    {N1, _, _} = vann(N, Env),
    Tree1 = rewrite(Tree, erl_syntax:function(N1, Cs1)),
    Bound = [],
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_fun_expr(Tree, Env) ->
    Cs = erl_syntax:fun_expr_clauses(Tree),
    {Cs1, {_, Free}} = vann_clauses(Cs, Env),
    Tree1 = rewrite(Tree, erl_syntax:fun_expr(Cs1)),
    Bound = [],
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_named_fun_expr(Tree, Env) ->
    N = erl_syntax:named_fun_expr_name(Tree),
    NBound = [erl_syntax:variable_name(N)],
    NFree = [],
    N1 = ann_bindings(N, Env, NBound, NFree),
    Env1 = ordsets:union(Env, NBound),
    Cs = erl_syntax:named_fun_expr_clauses(Tree),
    {Cs1, {_, Free}} = vann_clauses(Cs, Env1),
    Tree1 = rewrite(Tree, erl_syntax:named_fun_expr(N1,Cs1)),
    Bound = [],
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_match_expr(Tree, Env) ->
    E = erl_syntax:match_expr_body(Tree),
    {E1, Bound1, Free1} = vann(E, Env),
    Env1 = ordsets:union(Env, Bound1),
    P = erl_syntax:match_expr_pattern(Tree),
    {P1, Bound2, Free2} = vann_pattern(P, Env1),
    Bound = ordsets:union(Bound1, Bound2),
    Free = ordsets:union(Free1, Free2),
    Tree1 = rewrite(Tree, erl_syntax:match_expr(P1, E1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_case_expr(Tree, Env) ->
    E = erl_syntax:case_expr_argument(Tree),
    {E1, Bound1, Free1} = vann(E, Env),
    Env1 = ordsets:union(Env, Bound1),
    Cs = erl_syntax:case_expr_clauses(Tree),
    {Cs1, {Bound2, Free2}} = vann_clauses(Cs, Env1),
    Bound = ordsets:union(Bound1, Bound2),
    Free = ordsets:union(Free1, Free2),
    Tree1 = rewrite(Tree, erl_syntax:case_expr(E1, Cs1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_if_expr(Tree, Env) ->
    Cs = erl_syntax:if_expr_clauses(Tree),
    {Cs1, {Bound, Free}} = vann_clauses(Cs, Env),
    Tree1 = rewrite(Tree, erl_syntax:if_expr(Cs1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_catch_expr(Tree, Env) ->
    E = erl_syntax:catch_expr_body(Tree),
    {E1, _, Free} = vann(E, Env),
    Tree1 = rewrite(Tree, erl_syntax:catch_expr(E1)),
    Bound = [],
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_try_expr(Tree, Env) ->
    Es = erl_syntax:try_expr_body(Tree),
    {Es1, {Bound1, Free1}} = vann_body(Es, Env),
    Cs = erl_syntax:try_expr_clauses(Tree),
    %% bindings in the body should be available in the success case,
    {Cs1, {_, Free2}} = vann_clauses(Cs, ordsets:union(Env, Bound1)),
    Hs = erl_syntax:try_expr_handlers(Tree),
    {Hs1, {_, Free3}} = vann_clauses(Hs, Env),
    %% the after part does not export anything, yet; this might change
    As = erl_syntax:try_expr_after(Tree),
    {As1, {_, Free4}} = vann_body(As, Env),
    Tree1 = rewrite(Tree, erl_syntax:try_expr(Es1, Cs1, Hs1, As1)),
    Bound = [],
    Free = ordsets:union(Free1, ordsets:union(Free2, ordsets:union(Free3, Free4))),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_receive_expr(Tree, Env) ->
    %% The timeout action is treated as an extra clause.
    %% Bindings in the expiry expression are local only.
    Cs = erl_syntax:receive_expr_clauses(Tree),
    Es = erl_syntax:receive_expr_action(Tree),
    C = erl_syntax:clause([], Es),
    {[C1 | Cs1], {Bound, Free1}} = vann_clauses([C | Cs], Env),
    Es1 = erl_syntax:clause_body(C1),
    {T1, _, Free2} = case erl_syntax:receive_expr_timeout(Tree) of
                         none ->
                             {none, [], []};
                         T ->
                             vann(T, Env)
                     end,
    Free = ordsets:union(Free1, Free2),
    Tree1 = rewrite(Tree, erl_syntax:receive_expr(Cs1, T1, Es1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_list_comp(Tree, Env) ->
    Es = erl_syntax:list_comp_body(Tree),
    {Es1, {Bound1, Free1}} = vann_list_comp_body(Es, Env),
    Env1 = ordsets:union(Env, Bound1),
    T = erl_syntax:list_comp_template(Tree),
    {T1, _, Free2} = vann(T, Env1),
    Free = ordsets:union(Free1, ordsets:subtract(Free2, Bound1)),
    Bound = [],
    Tree1 = rewrite(Tree, erl_syntax:list_comp(T1, Es1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_list_comp_body_join() ->
    fun (T, {Env, Bound, Free}) ->
            {T1, Bound1, Free1} = case erl_syntax:type(T) of
                                      binary_generator ->
				          vann_binary_generator(T,Env);
				      generator ->
                                          vann_generator(T, Env);
                                      _ ->
                                          %% Bindings in filters are not
                                          %% exported to the rest of the
                                          %% body.
                                          {T2, _, Free2} = vann(T, Env),
                                          {T2, [], Free2}
                                  end,
            Env1 = ordsets:union(Env, Bound1),
            {T1, {Env1, ordsets:union(Bound, Bound1),
                  ordsets:union(Free, 
                                ordsets:subtract(Free1, Bound))}}
    end.

vann_list_comp_body(Ts, Env) ->
    F = vann_list_comp_body_join(),
    {Ts1, {_, Bound, Free}} = lists:mapfoldl(F, {Env, [], []}, Ts),
    {Ts1, {Bound, Free}}.

vann_binary_comp(Tree, Env) ->
    Es = erl_syntax:binary_comp_body(Tree),
    {Es1, {Bound1, Free1}} = vann_binary_comp_body(Es, Env),
    Env1 = ordsets:union(Env, Bound1),
    T = erl_syntax:binary_comp_template(Tree),
    {T1, _, Free2} = vann(T, Env1),
    Free = ordsets:union(Free1, ordsets:subtract(Free2, Bound1)),
    Bound = [],
    Tree1 = rewrite(Tree, erl_syntax:binary_comp(T1, Es1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_binary_comp_body_join() ->
    fun (T, {Env, Bound, Free}) ->
            {T1, Bound1, Free1} = case erl_syntax:type(T) of
                                    binary_generator ->
				          vann_binary_generator(T, Env);
				    generator ->
                                          vann_generator(T, Env);
                                      _ ->
                                          %% Bindings in filters are not
                                          %% exported to the rest of the
                                          %% body.
                                          {T2, _, Free2} = vann(T, Env),
                                          {T2, [], Free2}
                                  end,
            Env1 = ordsets:union(Env, Bound1),
            {T1, {Env1, ordsets:union(Bound, Bound1),
                  ordsets:union(Free, 
                                ordsets:subtract(Free1, Bound))}}
    end.

vann_binary_comp_body(Ts, Env) ->
    F = vann_binary_comp_body_join(),
    {Ts1, {_, Bound, Free}} = lists:mapfoldl(F, {Env, [], []}, Ts),
    {Ts1, {Bound, Free}}.

%% In list comprehension generators, the pattern variables are always
%% viewed as new occurrences, shadowing whatever is in the input
%% environment (thus, the pattern contains no variable uses, only
%% bindings). Bindings in the generator body are not exported.

vann_generator(Tree, Env) ->
    P = erl_syntax:generator_pattern(Tree),
    {P1, Bound, _} = vann_pattern(P, []),
    E = erl_syntax:generator_body(Tree),
    {E1, _, Free} = vann(E, Env),
    Tree1 = rewrite(Tree, erl_syntax:generator(P1, E1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_binary_generator(Tree, Env) ->
    P = erl_syntax:binary_generator_pattern(Tree),
    {P1, Bound, _} = vann_pattern(P, Env),
    E = erl_syntax:binary_generator_body(Tree),
    {E1, _, Free} = vann(E, Env),
    Tree1 = rewrite(Tree, erl_syntax:binary_generator(P1, E1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_block_expr(Tree, Env) ->
    Es = erl_syntax:block_expr_body(Tree),
    {Es1, {Bound, Free}} = vann_body(Es, Env),
    Tree1 = rewrite(Tree, erl_syntax:block_expr(Es1)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_body_join() ->
    fun (T, {Env, Bound, Free}) ->
            {T1, Bound1, Free1} = vann(T, Env),
            Env1 = ordsets:union(Env, Bound1),
            {T1, {Env1, ordsets:union(Bound, Bound1),
                  ordsets:union(Free,
                                ordsets:subtract(Free1, Bound))}}
    end.

vann_body(Ts, Env) ->
    {Ts1, {_, Bound, Free}} = lists:mapfoldl(vann_body_join(),
                                             {Env, [], []}, Ts),
    {Ts1, {Bound, Free}}.

%% Macro names must be ignored even if they happen to be variables,
%% lexically speaking.

vann_macro(Tree, Env) ->
    {As, {Bound, Free}} = case erl_syntax:macro_arguments(Tree) of
                              none ->
                                  {none, {[], []}};
                              As1 ->
                                  vann_list(As1, Env)
                          end,
    N = erl_syntax:macro_name(Tree),
    Tree1 = rewrite(Tree, erl_syntax:macro(N, As)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_pattern(Tree, Env) ->
    case erl_syntax:type(Tree) of
        variable ->
            V = erl_syntax:variable_name(Tree),
            case ordsets:is_element(V, Env) of
                true ->
                    %% Variable use
                    Bound = [],
                    Free = [V],
                    {ann_bindings(Tree, Env, Bound, Free), Bound, Free};
                false ->
                    %% Variable binding
                    Bound = [V],
                    Free = [],
                    {ann_bindings(Tree, Env, Bound, Free), Bound, Free}
            end;
        match_expr ->
            %% Alias pattern
            P = erl_syntax:match_expr_pattern(Tree),
            {P1, Bound1, Free1} = vann_pattern(P, Env),
            E = erl_syntax:match_expr_body(Tree),
            {E1, Bound2, Free2} = vann_pattern(E, Env),
            Bound = ordsets:union(Bound1, Bound2),
            Free = ordsets:union(Free1, Free2),
            Tree1 = rewrite(Tree, erl_syntax:match_expr(P1, E1)),
            {ann_bindings(Tree1, Env, Bound, Free), Bound, Free};
        macro ->
            %% The macro name must be ignored. The arguments are treated
            %% as patterns.
            {As, {Bound, Free}} =
                case erl_syntax:macro_arguments(Tree) of
                    none ->
                        {none, {[], []}};
                    As1 ->
                        vann_patterns(As1, Env)
                end,
            N = erl_syntax:macro_name(Tree),
            Tree1 = rewrite(Tree, erl_syntax:macro(N, As)),
            {ann_bindings(Tree1, Env, Bound, Free), Bound, Free};
        _Type ->
            F = vann_patterns_join(Env),
            {Tree1, {Bound, Free}} = mapfold_subtrees(F, {[], []},
                                                      Tree),
            {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}
    end.

vann_patterns_join(Env) ->
    fun (T, {Bound, Free}) ->
            {T1, Bound1, Free1} = vann_pattern(T, Env),
            {T1, {ordsets:union(Bound, Bound1),
                  ordsets:union(Free, Free1)}}
    end.

vann_patterns(Ps, Env) ->
    lists:mapfoldl(vann_patterns_join(Env), {[], []}, Ps).

vann_clause(C, Env) ->
    {Ps, {Bound1, Free1}} = vann_patterns(erl_syntax:clause_patterns(C),
                                          Env),
    Env1 = ordsets:union(Env, Bound1),
    %% Guards cannot add bindings
    {G1, _, Free2} = case erl_syntax:clause_guard(C) of
                         none ->
                             {none, [], []};
                         G ->
                             vann(G, Env1)
                     end,
    {Es, {Bound2, Free3}} = vann_body(erl_syntax:clause_body(C), Env1),
    Bound = ordsets:union(Bound1, Bound2),
    Free = ordsets:union(Free1,
                         ordsets:subtract(ordsets:union(Free2, Free3),
                                          Bound1)),
    Tree1 = rewrite(C, erl_syntax:clause(Ps, G1, Es)),
    {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.

vann_clauses_join(Env) ->
    fun (C, {Bound, Free}) ->
            {C1, Bound1, Free1} = vann_clause(C, Env),
            {C1, {ordsets:intersection(Bound, Bound1),
                  ordsets:union(Free, Free1)}}
    end.

vann_clauses([C | Cs], Env) ->
    {C1, Bound, Free} = vann_clause(C, Env),
    {Cs1, BF} = lists:mapfoldl(vann_clauses_join(Env), {Bound, Free}, Cs),
    {[C1 | Cs1], BF};
vann_clauses([], _Env) ->
    {[], {[], []}}.

ann_bindings(Tree, Env, Bound, Free) ->
    As0 = erl_syntax:get_ann(Tree),
    As1 = [{env, Env},
           {bound, Bound},
           {free, Free}
           | delete_binding_anns(As0)],
    erl_syntax:set_ann(Tree, As1).

delete_binding_anns([{env, _} | As]) ->
    delete_binding_anns(As);
delete_binding_anns([{bound, _} | As]) ->
    delete_binding_anns(As);
delete_binding_anns([{free, _} | As]) ->
    delete_binding_anns(As);
delete_binding_anns([A | As]) ->
    [A | delete_binding_anns(As)];
delete_binding_anns([]) ->
    [].


%% =====================================================================
%% @spec is_fail_expr(Tree::syntaxTree()) -> boolean()
%%
%% @doc Returns `true' if `Tree' represents an
%% expression which never terminates normally. Note that the reverse
%% does not apply. Currently, the detected cases are calls to
%% `exit/1', `throw/1',
%% `erlang:error/1' and `erlang:error/2'.
%%
%% @see //erts/erlang:exit/1
%% @see //erts/erlang:throw/1
%% @see //erts/erlang:error/1
%% @see //erts/erlang:error/2

-doc """
Returns `true` if `Tree` represents an expression which never terminates
normally. Note that the reverse does not apply. Currently, the detected cases
are calls to [`exit/1`](`exit/1`), [`throw/1`](`throw/1`), `erlang:error/1` and
`erlang:error/2`.

_See also: _[//erts/erlang:error/1](`erlang:error/1`),
[//erts/erlang:error/2](`erlang:error/2`),
[//erts/erlang:exit/1](`erlang:exit/1`),
[//erts/erlang:throw/1](`erlang:throw/1`).
""".
-spec is_fail_expr(syntaxTree()) -> boolean().

is_fail_expr(E) ->          
    case erl_syntax:type(E) of
        application ->
            N = length(erl_syntax:application_arguments(E)),
            F = erl_syntax:application_operator(E),
            case catch {ok, analyze_function_name(F)} of
                syntax_error ->
                    false;
                {ok, exit} when N =:= 1 ->
                    true;
                {ok, throw} when N =:= 1 ->
                    true;
                {ok, {erlang, exit}} when N =:= 1 ->
                    true;
                {ok, {erlang, throw}} when N =:= 1 ->
                    true;
                {ok, {erlang, error}} when N =:= 1 ->
                    true;
                {ok, {erlang, error}} when N =:= 2 ->
                    true;
                {ok, {erlang, fault}} when N =:= 1 ->
                    true;
                {ok, {erlang, fault}} when N =:= 2 ->
                    true;
                _ ->
                    false
            end;
        _ ->
            false
    end.


%% =====================================================================
%% @spec analyze_forms(Forms) -> [{Key, term()}]
%%
%%          Forms = syntaxTree() | [syntaxTree()]
%%          Key = attributes | errors | exports | functions | imports
%%                | module | records | warnings
%%
%% @doc Analyzes a sequence of "program forms". The given
%% `Forms' may be a single syntax tree of type
%% `form_list', or a list of "program form" syntax trees. The
%% returned value is a list of pairs `{Key, Info}', where
%% each value of `Key' occurs at most once in the list; the
%% absence of a particular key indicates that there is no well-defined
%% value for that key.
%%
%% Each entry in the resulting list contains the following
%% corresponding information about the program forms:
%% <dl>
%%     <dt>`{attributes, Attributes}'</dt>
%%       <dd><ul>
%% 	   <li>`Attributes = [{atom(), term()}]'</li>
%%       </ul>
%% 	 `Attributes' is a list of pairs representing the
%% 	 names and corresponding values of all so-called "wild"
%% 	 attributes (as e.g. "`-compile(...)'") occurring in
%% 	 `Forms' (cf. `analyze_wild_attribute/1').
%% 	 We do not guarantee that each name occurs at most once in the
%% 	 list. The order of listing is not defined.</dd>
%%
%%     <dt>`{errors, Errors}'</dt>
%%       <dd><ul>
%% 	   <li>`Errors = [term()]'</li>
%%       </ul>
%% 	 `Errors' is the list of error descriptors of all
%% 	 `error_marker' nodes that occur in
%% 	 `Forms'. The order of listing is not defined.</dd>
%%
%%     <dt>`{exports, Exports}'</dt>
%%       <dd><ul>
%% 	    <li>`Exports = [FunctionName]'</li>
%% 	    <li>`FunctionName = atom()
%%                    | {atom(), integer()}
%% 		      | {ModuleName, FunctionName}'</li>
%% 	    <li>`ModuleName = atom()'</li>
%%       </ul>
%% 	 `Exports' is a list of representations of those
%% 	 function names that are listed by export declaration attributes
%% 	 in `Forms' (cf.
%% 	 `analyze_export_attribute/1'). We do not guarantee
%% 	 that each name occurs at most once in the list. The order of
%% 	 listing is not defined.</dd>
%%
%%     <dt>`{functions, Functions}'</dt>
%%       <dd><ul>
%% 	    <li>`Functions = [{atom(), integer()}]'</li>
%%       </ul>
%% 	 `Functions' is a list of the names of the functions
%% 	 that are defined in `Forms' (cf.
%% 	 `analyze_function/1'). We do not guarantee that each
%% 	 name occurs at most once in the list. The order of listing is
%% 	 not defined.</dd>
%%
%%     <dt>`{imports, Imports}'</dt>
%%       <dd><ul>
%% 	    <li>`Imports = [{Module, Names}]'</li>
%% 	    <li>`Module = atom()'</li>
%% 	    <li>`Names = [FunctionName]'</li>
%% 	    <li>`FunctionName = atom()
%%                    | {atom(), integer()}
%% 		      | {ModuleName, FunctionName}'</li>
%% 	    <li>`ModuleName = atom()'</li>
%%       </ul>
%% 	 `Imports' is a list of pairs representing those
%% 	 module names and corresponding function names that are listed
%% 	 by import declaration attributes in `Forms' (cf.
%% 	 `analyze_import_attribute/1'), where each
%% 	 `Module' occurs at most once in
%% 	 `Imports'. We do not guarantee that each name occurs
%% 	 at most once in the lists of function names. The order of
%% 	 listing is not defined.</dd>
%%
%%     <dt>`{module, ModuleName}'</dt>
%%       <dd><ul>
%% 	    <li>`ModuleName = atom()'</li>
%%       </ul>
%% 	 `ModuleName' is the name declared by a module
%% 	 attribute in `Forms'. If no module name is defined
%% 	 in `Forms', the result will contain no entry for the
%% 	 `module' key. If multiple module name declarations
%% 	 should occur, all but the first will be ignored.</dd>
%%
%%     <dt>`{records, Records}'</dt>
%%       <dd><ul>
%% 	    <li>`Records = [{atom(), Fields}]'</li>
%% 	    <li>`Fields = [{atom(), {Default, Type}}]'</li>
%% 	    <li>`Default = none | syntaxTree()'</li>
%% 	    <li>`Type = none | syntaxTree()'</li>
%%       </ul>
%% 	 `Records' is a list of pairs representing the names
%% 	 and corresponding field declarations of all record declaration
%% 	 attributes occurring in `Forms'. For fields declared
%% 	 without a default value, the corresponding value for
%% 	 `Default' is the atom `none'. Similarly, for fields declared
%%       without a type, the corresponding value for `Type' is the
%%       atom `none' (cf.
%% 	 `analyze_record_attribute/1'). We do not guarantee
%% 	 that each record name occurs at most once in the list. The
%% 	 order of listing is not defined.</dd>
%%
%%     <dt>`{warnings, Warnings}'</dt>
%%       <dd><ul>
%% 	    <li>`Warnings = [term()]'</li>
%%       </ul>
%% 	 `Warnings' is the list of error descriptors of all
%% 	 `warning_marker' nodes that occur in
%% 	 `Forms'. The order of listing is not defined.</dd>
%% </dl>
%%
%% The evaluation throws `syntax_error' if an ill-formed
%% Erlang construct is encountered.
%%
%% @see analyze_wild_attribute/1
%% @see analyze_export_attribute/1
%% @see analyze_function/1
%% @see analyze_import_attribute/1
%% @see analyze_record_attribute/1
%% @see erl_syntax:error_marker_info/1
%% @see erl_syntax:warning_marker_info/1

-type key() :: 'attributes' | 'errors' | 'exports' | 'functions' | 'imports'
             | 'module' | 'records' | 'warnings'.
-type info_pair() :: {key(), term()}.

-doc """
Analyzes a sequence of "program forms". The given `Forms` may be a single syntax
tree of type `form_list`, or a list of "program form" syntax trees. The returned
value is a list of pairs `{Key, Info}`, where each value of `Key` occurs at most
once in the list; the absence of a particular key indicates that there is no
well-defined value for that key.

Each entry in the resulting list contains the following corresponding
information about the program forms:

- **`{attributes, Attributes}`**

  - `Attributes = [{atom(), term()}]`

  `Attributes` is a list of pairs representing the names and corresponding
  values of all so-called "wild" attributes (as e.g. "`-compile(...)`")
  occurring in `Forms` (cf.
  [`analyze_wild_attribute/1`](`analyze_wild_attribute/1`)). We do not guarantee
  that each name occurs at most once in the list. The order of listing is not
  defined.

- **`{errors, Errors}`**

  - `Errors = [term()]`

  `Errors` is the list of error descriptors of all `error_marker` nodes that
  occur in `Forms`. The order of listing is not defined.

- **`{exports, Exports}`**

  - `Exports = [FunctionName]`
  - `FunctionName = atom() | {atom(), integer()} | {ModuleName, FunctionName}`
  - `ModuleName = atom()`

  `Exports` is a list of representations of those function names that are listed
  by export declaration attributes in `Forms` (cf.
  [`analyze_export_attribute/1`](`analyze_export_attribute/1`)). We do not
  guarantee that each name occurs at most once in the list. The order of listing
  is not defined.

- **`{functions, Functions}`**

  - `Functions = [{atom(), integer()}]`

  `Functions` is a list of the names of the functions that are defined in
  `Forms` (cf. [`analyze_function/1`](`analyze_function/1`)). We do not
  guarantee that each name occurs at most once in the list. The order of listing
  is not defined.

- **`{imports, Imports}`**

  - `Imports = [{Module, Names}]`
  - `Module = atom()`
  - `Names = [FunctionName]`
  - `FunctionName = atom() | {atom(), integer()} | {ModuleName, FunctionName}`
  - `ModuleName = atom()`

  `Imports` is a list of pairs representing those module names and corresponding
  function names that are listed by import declaration attributes in `Forms`
  (cf. [`analyze_import_attribute/1`](`analyze_import_attribute/1`)), where each
  `Module` occurs at most once in `Imports`. We do not guarantee that each name
  occurs at most once in the lists of function names. The order of listing is
  not defined.

- **`{module, ModuleName}`**

  - `ModuleName = atom()`

  `ModuleName` is the name declared by a module attribute in `Forms`. If no
  module name is defined in `Forms`, the result will contain no entry for the
  `module` key. If multiple module name declarations should occur, all but the
  first will be ignored.

- **`{records, Records}`**

  - `Records = [{atom(), Fields}]`
  - `Fields = [{atom(), {Default, Type}}]`
  - `Default = none | syntaxTree()`
  - `Type = none | syntaxTree()`

  `Records` is a list of pairs representing the names and corresponding field
  declarations of all record declaration attributes occurring in `Forms`. For
  fields declared without a default value, the corresponding value for `Default`
  is the atom `none`. Similarly, for fields declared without a type, the
  corresponding value for `Type` is the atom `none` (cf.
  [`analyze_record_attribute/1`](`analyze_record_attribute/1`)). We do not
  guarantee that each record name occurs at most once in the list. The order of
  listing is not defined.

- **`{warnings, Warnings}`**

  - `Warnings = [term()]`

  `Warnings` is the list of error descriptors of all `warning_marker` nodes that
  occur in `Forms`. The order of listing is not defined.

The evaluation throws `syntax_error` if an ill-formed Erlang construct is
encountered.

_See also: _`analyze_export_attribute/1`, `analyze_function/1`,
`analyze_import_attribute/1`, `analyze_record_attribute/1`,
`analyze_wild_attribute/1`, `erl_syntax:error_marker_info/1`,
`erl_syntax:warning_marker_info/1`.
""".
-spec analyze_forms(erl_syntax:forms()) -> [info_pair()].

analyze_forms(Forms) when is_list(Forms) ->
    finfo_to_list(lists:foldl(fun collect_form/2, new_finfo(), Forms));
analyze_forms(Forms) ->
    analyze_forms(
      erl_syntax:form_list_elements(
        erl_syntax:flatten_form_list(Forms))).

collect_form(Node, Info) ->
    case analyze_form(Node) of
        {attribute, {Name, Data}} ->
            collect_attribute(Name, Data, Info);
        {attribute, preprocessor} ->
            Info;
        {function, Name} ->
            finfo_add_function(Name, Info);
        {error_marker, Data} ->
            finfo_add_error(Data, Info);
        {warning_marker, Data} ->
            finfo_add_warning(Data, Info);
        _ ->
            Info
    end.

collect_attribute(module, M, Info) ->
    finfo_set_module(M, Info);
collect_attribute(export, L, Info) ->
    finfo_add_exports(L, Info);
collect_attribute(import, {M, L}, Info) ->
    finfo_add_imports(M, L, Info);
collect_attribute(import, M, Info) ->
    finfo_add_module_import(M, Info);
collect_attribute(file, _, Info) ->
    Info;
collect_attribute(record, {R, L}, Info) ->
    finfo_add_record(R, L, Info);
collect_attribute(N, V, Info) ->
    finfo_add_attribute(N, V, Info).

%% Abstract datatype for collecting module information.

-record(forms, {module         = none :: 'none' | {'value', atom()},
		exports        = []   :: [{atom(), arity()}],
		module_imports = []   :: [atom()],
		imports        = []   :: [{atom(), [{atom(), arity()}]}],
		attributes     = []   :: [{atom(), term()}],
		records        = []   :: [{atom(), [{atom(),
                                                     field_default(),
                                                     field_type()}]}],
		errors         = []   :: [term()],
		warnings       = []   :: [term()],
		functions      = []   :: [{atom(), arity()}]}).

-type field_default() :: 'none' | syntaxTree().
-type field_type()    :: 'none' | syntaxTree().

new_finfo() ->
    #forms{}.

finfo_set_module(Name, Info) ->
    case Info#forms.module of
        none ->
            Info#forms{module = {value, Name}};
        {value, _} ->
            Info
    end.

finfo_add_exports(L, Info) ->
    Info#forms{exports = L ++ Info#forms.exports}.

finfo_add_module_import(M, Info) ->
    Info#forms{module_imports = [M | Info#forms.module_imports]}.

finfo_add_imports(M, L, Info) ->
    Es = Info#forms.imports,
    case lists:keyfind(M, 1, Es) of
        {_, L1} ->
            Es1 = lists:keyreplace(M, 1, Es, {M, L ++ L1}),
            Info#forms{imports = Es1};
        false ->
            Info#forms{imports = [{M, L} | Es]}
    end.

finfo_add_attribute(Name, Val, Info) ->
    Info#forms{attributes = [{Name, Val} | Info#forms.attributes]}.

finfo_add_record(R, L, Info) ->
    Info#forms{records = [{R, L} | Info#forms.records]}.

finfo_add_error(R, Info) ->
    Info#forms{errors = [R | Info#forms.errors]}.

finfo_add_warning(R, Info) ->
    Info#forms{warnings = [R | Info#forms.warnings]}.

finfo_add_function(F, Info) ->
    Info#forms{functions = [F | Info#forms.functions]}.

finfo_to_list(Info) ->
    [{Key, Value}
     || {Key, {value, Value}} <-
            [{module, Info#forms.module},
             {exports, list_value(Info#forms.exports)},
             {imports, list_value(Info#forms.imports)},
             {module_imports, list_value(Info#forms.module_imports)},
             {attributes, list_value(Info#forms.attributes)},
             {records, list_value(Info#forms.records)},
             {errors, list_value(Info#forms.errors)},
             {warnings, list_value(Info#forms.warnings)},
             {functions, list_value(Info#forms.functions)}
            ]].

list_value([]) ->
    none;
list_value(List) ->
    {value, List}.


%% =====================================================================
%% @spec analyze_form(Node::syntaxTree()) -> {atom(), term()} | atom()
%%
%% @doc Analyzes a "source code form" node. If `Node' is a
%% "form" type (cf. `erl_syntax:is_form/1'), the returned
%% value is a tuple `{Type, Info}' where `Type' is
%% the node type and `Info' depends on `Type', as
%% follows:
%% <dl>
%%   <dt>`{attribute, Info}'</dt>
%%
%%      <dd>where `Info = analyze_attribute(Node)'.</dd>
%%
%%   <dt>`{error_marker, Info}'</dt>
%%
%% 	<dd>where `Info =
%% 	erl_syntax:error_marker_info(Node)'.</dd>
%%
%%   <dt>`{function, Info}'</dt>
%%
%% 	    <dd>where `Info = analyze_function(Node)'.</dd>
%%
%%   <dt>`{warning_marker, Info}'</dt>
%%
%% 	    <dd>where `Info =
%% 	    erl_syntax:warning_marker_info(Node)'.</dd>
%% </dl>
%% For other types of forms, only the node type is returned.
%%
%% The evaluation throws `syntax_error' if
%% `Node' is not well-formed.
%%
%% @see analyze_attribute/1
%% @see analyze_function/1
%% @see erl_syntax:is_form/1
%% @see erl_syntax:error_marker_info/1
%% @see erl_syntax:warning_marker_info/1

-doc """
Analyzes a "source code form" node. If `Node` is a "form" type (cf.
`erl_syntax:is_form/1`), the returned value is a tuple `{Type, Info}` where
`Type` is the node type and `Info` depends on `Type`, as follows:

- **`{attribute, Info}`** - where `Info = analyze_attribute(Node)`.

- **`{error_marker, Info}`** - where
  `Info = erl_syntax:error_marker_info(Node)`.

- **`{function, Info}`** - where `Info = analyze_function(Node)`.

- **`{warning_marker, Info}`** - where
  `Info = erl_syntax:warning_marker_info(Node)`.

For other types of forms, only the node type is returned.

The evaluation throws `syntax_error` if `Node` is not well-formed.

_See also: _`analyze_attribute/1`, `analyze_function/1`,
`erl_syntax:error_marker_info/1`, `erl_syntax:is_form/1`,
`erl_syntax:warning_marker_info/1`.
""".
-spec analyze_form(syntaxTree()) -> {atom(), term()} | atom().

analyze_form(Node) ->
    case erl_syntax:type(Node) of
        attribute ->
            {attribute, analyze_attribute(Node)};
        function ->
            {function, analyze_function(Node)};
        error_marker ->
            {error_marker, erl_syntax:error_marker_info(Node)};
        warning_marker ->
            {warning_marker, erl_syntax:warning_marker_info(Node)};
        _ ->
            case erl_syntax:is_form(Node) of
                true ->
                    erl_syntax:type(Node);
                false ->
                    throw(syntax_error)
            end
    end.

%% =====================================================================
%% @spec analyze_attribute(Node::syntaxTree()) ->
%%           preprocessor | {atom(), atom()}
%%
%% @doc Analyzes an attribute node. If `Node' represents a
%% preprocessor directive, the atom `preprocessor' is
%% returned. Otherwise, if `Node' represents a module
%% attribute "`-Name...'", a tuple `{Name,
%% Info}' is returned, where `Info' depends on
%% `Name', as follows:
%% <dl>
%%     <dt>`{module, Info}'</dt>
%%
%% 	    <dd>where `Info =
%% 	    analyze_module_attribute(Node)'.</dd>
%%
%%     <dt>`{export, Info}'</dt>
%%
%% 	    <dd>where `Info =
%% 	    analyze_export_attribute(Node)'.</dd>
%%
%%     <dt>`{import, Info}'</dt>
%%
%% 	    <dd>where `Info =
%% 	    analyze_import_attribute(Node)'.</dd>
%%
%%     <dt>`{file, Info}'</dt>
%%
%% 	    <dd>where `Info =
%% 	    analyze_file_attribute(Node)'.</dd>
%%
%%     <dt>`{record, Info}'</dt>
%%
%% 	    <dd>where `Info =
%% 	    analyze_record_attribute(Node)'.</dd>
%%
%%     <dt>`{Name, Info}'</dt>
%%
%% 	    <dd>where `{Name, Info} =
%% 	    analyze_wild_attribute(Node)'.</dd>
%% </dl>
%% The evaluation throws `syntax_error' if `Node'
%% does not represent a well-formed module attribute.
%%
%% @see analyze_module_attribute/1
%% @see analyze_export_attribute/1
%% @see analyze_import_attribute/1
%% @see analyze_file_attribute/1
%% @see analyze_record_attribute/1
%% @see analyze_wild_attribute/1

-doc """
Analyzes an attribute node. If `Node` represents a preprocessor directive, the
atom `preprocessor` is returned. Otherwise, if `Node` represents a module
attribute "`-Name...`", a tuple `{Name, Info}` is returned, where `Info` depends
on `Name`, as follows:

- **`{module, Info}`** - where `Info = analyze_module_attribute(Node)`.

- **`{export, Info}`** - where `Info = analyze_export_attribute(Node)`.

- **`{import, Info}`** - where `Info = analyze_import_attribute(Node)`.

- **`{file, Info}`** - where `Info = analyze_file_attribute(Node)`.

- **`{record, Info}`** - where `Info = analyze_record_attribute(Node)`.

- **`{Name, Info}`** - where `{Name, Info} = analyze_wild_attribute(Node)`.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
module attribute.

_See also: _`analyze_export_attribute/1`, `analyze_file_attribute/1`,
`analyze_import_attribute/1`, `analyze_module_attribute/1`,
`analyze_record_attribute/1`, `analyze_wild_attribute/1`.
""".
-spec analyze_attribute(syntaxTree()) ->
        'preprocessor' | {atom(), term()}.  % XXX: underspecified

analyze_attribute(Node) ->
    Name = erl_syntax:attribute_name(Node),
    case erl_syntax:type(Name) of
        atom ->
            case erl_syntax:atom_value(Name) of
                define -> preprocessor;
                undef -> preprocessor;
                include -> preprocessor;
                include_lib -> preprocessor;
                ifdef -> preprocessor;
                ifndef -> preprocessor;
                'if' -> preprocessor;
                elif -> preprocessor;
                'else' -> preprocessor;
                endif -> preprocessor;
                A ->
                    {A, analyze_attribute(A, Node)}
            end;
        _ ->
            throw(syntax_error)
    end.

analyze_attribute(module, Node) ->
    analyze_module_attribute(Node);
analyze_attribute(export, Node) ->
    analyze_export_attribute(Node);
analyze_attribute(import, Node) ->
    analyze_import_attribute(Node);
analyze_attribute(file, Node) ->
    analyze_file_attribute(Node);
analyze_attribute(record, Node) ->
    analyze_record_attribute(Node);
analyze_attribute(_, Node) ->
    %% A "wild" attribute (such as e.g. a `compile' directive).
    {_, Info} = analyze_wild_attribute(Node),
    Info.


%% =====================================================================
%% @spec analyze_module_attribute(Node::syntaxTree()) ->
%%           Name::atom() | {Name::atom(), Variables::[atom()]}
%%
%% @doc Returns the module name and possible parameters declared by a
%% module attribute. If the attribute is a plain module declaration such
%% as `-module(name)', the result is the module name. If the attribute
%% is a parameterized module declaration, the result is a tuple
%% containing the module name and a list of the parameter variable
%% names.
%%
%% The evaluation throws `syntax_error' if `Node' does not represent a
%% well-formed module attribute.
%%
%% @see analyze_attribute/1

-doc """
Returns the module name and possible parameters declared by a module attribute.
If the attribute is a plain module declaration such as `-module(name)`, the
result is the module name. If the attribute is a parameterized module
declaration, the result is a tuple containing the module name and a list of the
parameter variable names.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
module attribute.

_See also: _`analyze_attribute/1`.
""".
-spec analyze_module_attribute(syntaxTree()) ->
        atom() | {atom(), [atom()]}.

analyze_module_attribute(Node) ->
    case erl_syntax:type(Node) of
        attribute ->
            case erl_syntax:attribute_arguments(Node) of
                [M] ->
                    module_name_to_atom(M);
                [M, L] ->
		    M1 = module_name_to_atom(M),
		    L1 = analyze_variable_list(L),
		    {M1, L1};
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.

analyze_variable_list(Node) ->
    case erl_syntax:is_proper_list(Node) of
        true ->
            [erl_syntax:variable_name(V)
	     || V <- erl_syntax:list_elements(Node)];
        false ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_export_attribute(Node::syntaxTree()) -> [FunctionName]
%%
%%          FunctionName = atom() | {atom(), integer()}
%%                       | {ModuleName, FunctionName}
%%          ModuleName = atom()
%%
%% @doc Returns the list of function names declared by an export
%% attribute. We do not guarantee that each name occurs at most once in
%% the list. The order of listing is not defined.
%%
%% The evaluation throws `syntax_error' if `Node' does not represent a
%% well-formed export attribute.
%%
%% @see analyze_attribute/1

-type functionN()    :: atom() | {atom(), arity()}.
-type functionName() :: functionN() | {atom(), functionN()}.

-doc """
Returns the list of function names declared by an export attribute. We do not
guarantee that each name occurs at most once in the list. The order of listing
is not defined.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
export attribute.

_See also: _`analyze_attribute/1`.
""".
-spec analyze_export_attribute(syntaxTree()) -> [functionName()].

analyze_export_attribute(Node) ->
    case erl_syntax:type(Node) of
        attribute ->
            case erl_syntax:attribute_arguments(Node) of
                [L] ->
                    analyze_function_name_list(L);
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.

analyze_function_name_list(Node) ->
    case erl_syntax:is_proper_list(Node) of
        true ->
            [analyze_function_name(F)
             || F <- erl_syntax:list_elements(Node)];
        false ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_function_name(Node::syntaxTree()) -> FunctionName
%%
%%          FunctionName = atom() | {atom(), integer()}
%%                       | {ModuleName, FunctionName}
%%          ModuleName = atom()
%%
%% @doc Returns the function name represented by a syntax tree. If
%% `Node' represents a function name, such as
%% "`foo/1'" or "`bloggs:fred/2'", a uniform
%% representation of that name is returned. Different nestings of arity
%% and module name qualifiers in the syntax tree does not affect the
%% result.
%%
%% The evaluation throws `syntax_error' if
%% `Node' does not represent a well-formed function name.

-doc """
Returns the function name represented by a syntax tree. If `Node` represents a
function name, such as "`foo/1`" or "`bloggs:fred/2`", a uniform representation
of that name is returned. Different nestings of arity and module name qualifiers
in the syntax tree does not affect the result.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
function name.
""".
-spec analyze_function_name(syntaxTree()) -> functionName().

analyze_function_name(Node) ->
    case erl_syntax:type(Node) of
        atom ->
            erl_syntax:atom_value(Node);
        arity_qualifier ->
            A = erl_syntax:arity_qualifier_argument(Node),
            case erl_syntax:type(A) of
                integer ->
                    F = erl_syntax:arity_qualifier_body(Node),
                    F1 = analyze_function_name(F),
                    append_arity(erl_syntax:integer_value(A), F1);
                _ ->
                    throw(syntax_error)
            end;
        module_qualifier ->
            M = erl_syntax:module_qualifier_argument(Node),
            case erl_syntax:type(M) of
                atom ->
                    F = erl_syntax:module_qualifier_body(Node),
                    F1 = analyze_function_name(F),
                    {erl_syntax:atom_value(M), F1};
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.

append_arity(A, {Module, Name}) ->
    {Module, append_arity(A, Name)};
append_arity(A, Name) when is_atom(Name) ->
    {Name, A};
append_arity(A, A) ->
    A;
append_arity(_A, Name) ->
    Name.    % quietly drop extra arity in case of conflict


%% =====================================================================
%% @spec analyze_import_attribute(Node::syntaxTree()) ->
%%           {atom(), [FunctionName]} | atom()
%%
%%          FunctionName = atom() | {atom(), integer()}
%%                       | {ModuleName, FunctionName}
%%          ModuleName = atom()
%%
%% @doc Returns the module name and (if present) list of function names
%% declared by an import attribute. The returned value is an atom
%% `Module' or a pair `{Module, Names}', where
%% `Names' is a list of function names declared as imported
%% from the module named by `Module'. We do not guarantee
%% that each name occurs at most once in `Names'. The order
%% of listing is not defined.
%%
%% The evaluation throws `syntax_error' if `Node' does not represent a
%% well-formed import attribute.
%%
%% @see analyze_attribute/1

-doc """
Returns the module name and (if present) list of function names declared by an
import attribute. The returned value is an atom `Module` or a pair
`{Module, Names}`, where `Names` is a list of function names declared as
imported from the module named by `Module`. We do not guarantee that each name
occurs at most once in `Names`. The order of listing is not defined.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
import attribute.

_See also: _`analyze_attribute/1`.
""".
-spec analyze_import_attribute(syntaxTree()) ->
        {atom(), [functionName()]} | atom().

analyze_import_attribute(Node) ->
    case erl_syntax:type(Node) of
        attribute ->
            case erl_syntax:attribute_arguments(Node) of
		[M] ->
		    module_name_to_atom(M);
		[M, L] ->
		    M1 = module_name_to_atom(M),
		    L1 = analyze_function_name_list(L),
		    {M1, L1};
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_type_name(Node::syntaxTree()) -> TypeName
%%
%%          TypeName = atom()
%%                   | {atom(), integer()}
%%                   | {ModuleName, {atom(), integer()}}
%%          ModuleName = atom()
%%
%% @doc Returns the type name represented by a syntax tree. If
%% `Node' represents a type name, such as
%% "`foo/1'" or "`bloggs:fred/2'", a uniform
%% representation of that name is returned.
%%
%% The evaluation throws `syntax_error' if
%% `Node' does not represent a well-formed type name.

-doc """
Returns the type name represented by a syntax tree. If `Node` represents a type
name, such as "`foo/1`" or "`bloggs:fred/2`", a uniform representation of that
name is returned.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
type name.
""".
-spec analyze_type_name(syntaxTree()) -> typeName().

analyze_type_name(Node) ->
    case erl_syntax:type(Node) of
        atom ->
            erl_syntax:atom_value(Node);
        arity_qualifier ->
            A = erl_syntax:arity_qualifier_argument(Node),
            N = erl_syntax:arity_qualifier_body(Node),

            case ((erl_syntax:type(A) =:= integer)
                  and (erl_syntax:type(N) =:= atom))
            of
                true ->
                    append_arity(erl_syntax:integer_value(A),
                                 erl_syntax:atom_value(N));
                _ ->
                    throw(syntax_error)
            end;
        module_qualifier ->
            M = erl_syntax:module_qualifier_argument(Node),
            case erl_syntax:type(M) of
                atom ->
                    N = erl_syntax:module_qualifier_body(Node),
                    N1 = analyze_type_name(N),
                    {erl_syntax:atom_value(M), N1};
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.

%% =====================================================================
%% @spec analyze_wild_attribute(Node::syntaxTree()) -> {atom(), term()}
%%
%% @doc Returns the name and value of a "wild" attribute. The result is
%% the pair `{Name, Value}', if `Node' represents "`-Name(Value)'".
%%
%% Note that no checking is done whether `Name' is a
%% reserved attribute name such as `module' or
%% `export': it is assumed that the attribute is "wild".
%%
%% The evaluation throws `syntax_error' if `Node' does not represent a
%% well-formed wild attribute.
%%
%% @see analyze_attribute/1

-doc """
Returns the name and value of a "wild" attribute. The result is the pair
`{Name, Value}`, if `Node` represents "`-Name(Value)`".

Note that no checking is done whether `Name` is a reserved attribute name such
as `module` or `export`: it is assumed that the attribute is "wild".

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
wild attribute.

_See also: _`analyze_attribute/1`.
""".
-spec analyze_wild_attribute(syntaxTree()) -> {atom(), term()}.

analyze_wild_attribute(Node) ->
    case erl_syntax:type(Node) of
        attribute ->
            N = erl_syntax:attribute_name(Node),
            case erl_syntax:type(N) of
                atom ->
                    case erl_syntax:attribute_arguments(Node) of
                        [V] ->
                            %% Note: does not work well with macros.
			    case catch {ok, erl_syntax:concrete(V)} of
				{ok, Val} ->
				    {erl_syntax:atom_value(N), Val};
				_ ->
				    throw(syntax_error)
			    end;
                        _ ->
                            throw(syntax_error)
                    end;
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_record_attribute(Node::syntaxTree()) ->
%%           {atom(), Fields}
%%
%% 	    Fields = [{atom(), {Default, Type}}]
%% 	    Default = none | syntaxTree()
%% 	    Type = none | syntaxTree()
%%
%% @doc Returns the name and the list of fields of a record declaration
%% attribute. The result is a pair `{Name, Fields}', if
%% `Node' represents "`-record(Name, {...}).'",
%% where `Fields' is a list of pairs `{Label,
%% {Default, Type}}' for each field "`Label'", "`Label =
%% Default'", "`Label :: Type'", or
%% "`Label = Default :: Type'" in the declaration,
%% listed in left-to-right
%% order. If the field has no default-value declaration, the value for
%% `Default' will be the atom `none'. If the field has no type declaration,
%% the value for `Type' will be the atom `none'. We do not
%% guarantee that each label occurs at most once in the list.
%%
%% The evaluation throws `syntax_error' if
%% `Node' does not represent a well-formed record declaration
%% attribute.
%%
%% @see analyze_attribute/1
%% @see analyze_record_field/1

-type field() :: {atom(), {field_default(), field_type()}}.

-type fields() :: [field()].

-doc """
Returns the name and the list of fields of a record declaration attribute. The
result is a pair `{Name, Fields}`, if `Node` represents
"`-record(Name, {...}).`", where `Fields` is a list of pairs
`{Label, {Default, Type}}` for each field "`Label`", "`Label = Default`",
"`Label :: Type`", or "`Label = Default :: Type`" in the declaration, listed in
left-to-right order. If the field has no default-value declaration, the value
for `Default` will be the atom `none`. If the field has no type declaration, the
value for `Type` will be the atom `none`. We do not guarantee that each label
occurs at most once in the list.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
record declaration attribute.

_See also: _`analyze_attribute/1`, `analyze_record_field/1`.
""".
-spec analyze_record_attribute(syntaxTree()) -> {atom(), fields()}.

analyze_record_attribute(Node) ->
    case erl_syntax:type(Node) of
        attribute ->
            case erl_syntax:attribute_arguments(Node) of
                [R, T] ->
                    case erl_syntax:type(R) of
                        atom ->
                            Es = analyze_record_attribute_tuple(T),
                            {erl_syntax:atom_value(R), Es};
                        _ ->
                            throw(syntax_error)
                    end;
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.

analyze_record_attribute_tuple(Node) ->
    case erl_syntax:type(Node) of
        tuple ->
            [analyze_record_field(F)
	     || F <- erl_syntax:tuple_elements(Node)];
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_record_expr(Node::syntaxTree()) ->
%%     {atom(), Info} | atom()
%%
%%    Info = {atom(), [{atom(), Value}]} | {atom(), atom()} | atom()
%%    Value = syntaxTree()
%%
%% @doc Returns the record name and field name/names of a record
%% expression. If `Node' has type `record_expr',
%% `record_index_expr' or `record_access', a pair
%% `{Type, Info}' is returned, otherwise an atom
%% `Type' is returned. `Type' is the node type of
%% `Node', and `Info' depends on
%% `Type', as follows:
%% <dl>
%%   <dt>`record_expr':</dt>
%%     <dd>`{atom(), [{atom(), Value}]}'</dd>
%%   <dt>`record_access':</dt>
%%     <dd>`{atom(), atom()}'</dd>
%%   <dt>`record_index_expr':</dt>
%%     <dd>`{atom(), atom()}'</dd>
%% </dl>
%%
%% For a `record_expr' node, `Info' represents
%% the record name and the list of descriptors for the involved fields,
%% listed in the order they appear. A field descriptor is a pair
%% `{Label, Value}', if `Node' represents "`Label = Value'".
%% For a `record_access' node,
%% `Info' represents the record name and the field name. For a
%% `record_index_expr' node, `Info' represents the
%% record name and the name field name.
%%
%% The evaluation throws `syntax_error' if
%% `Node' represents a record expression that is not
%% well-formed.
%%
%% @see analyze_record_attribute/1
%% @see analyze_record_field/1

-type info() :: {atom(), [{atom(), syntaxTree()}]}
              | {atom(), atom()} | atom().

-doc """
Returns the record name and field name/names of a record expression. If `Node`
has type `record_expr`, `record_index_expr` or `record_access`, a pair
`{Type, Info}` is returned, otherwise an atom `Type` is returned. `Type` is the
node type of `Node`, and `Info` depends on `Type`, as follows:

- **`record_expr`:** - `{atom(), [{atom(), Value}]}`

- **`record_access`:** - `{atom(), atom()}`

- **`record_index_expr`:** - `{atom(), atom()}`

For a `record_expr` node, `Info` represents the record name and the list of
descriptors for the involved fields, listed in the order they appear. A field
descriptor is a pair `{Label, Value}`, if `Node` represents "`Label = Value`".
For a `record_access` node, `Info` represents the record name and the field
name. For a `record_index_expr` node, `Info` represents the record name and the
name field name.

The evaluation throws `syntax_error` if `Node` represents a record expression
that is not well-formed.

_See also: _`analyze_record_attribute/1`, `analyze_record_field/1`.
""".
-spec analyze_record_expr(syntaxTree()) -> {atom(), info()} | atom().

analyze_record_expr(Node) ->
    case erl_syntax:type(Node) of
	record_expr ->
            A = erl_syntax:record_expr_type(Node),
            case erl_syntax:type(A) of
                atom ->
                    Fs0 = [analyze_record_field(F)
                           || F <- erl_syntax:record_expr_fields(Node)],
                    Fs = [{N, D} || {N, {D, _T}} <- Fs0],
                    {record_expr, {erl_syntax:atom_value(A), Fs}};
                _ ->
                    throw(syntax_error)
            end;
	record_access ->
	    F = erl_syntax:record_access_field(Node),
	    case erl_syntax:type(F) of
		atom ->
		    A = erl_syntax:record_access_type(Node),
                    case erl_syntax:type(A) of
                        atom ->
                            {record_access,
                             {erl_syntax:atom_value(A),
                              erl_syntax:atom_value(F)}};
                        _ ->
                            throw(syntax_error)
		    end;
		_ ->
		    throw(syntax_error)
	    end;
	record_index_expr ->
	    F = erl_syntax:record_index_expr_field(Node),
	    case erl_syntax:type(F) of
		atom ->
		    A = erl_syntax:record_index_expr_type(Node),
		    case erl_syntax:type(A) of
			atom ->
			    {record_index_expr,
			     {erl_syntax:atom_value(A),
			      erl_syntax:atom_value(F)}};
			_ ->
			    throw(syntax_error)
		    end;
		_ ->
		    throw(syntax_error)
	    end;
	Type ->
	    Type
    end.

%% =====================================================================
%% @spec analyze_record_field(Node::syntaxTree()) -> {atom(), {Default, Type}}
%%
%%          Default = none | syntaxTree()
%%          Type = none | syntaxTree()
%%
%% @doc Returns the label, value-expression, and type of a record field
%% specifier. The result is a pair `{Label, {Default, Type}}', if
%% `Node' represents "`Label'", "`Label = Default'",
%% "`Label :: Type'", or "`Label = Default :: Type'".
%% If the field has no value-expression, the value for
%% `Default' will be the atom `none'. If the field has no type,
%% the value for `Type' will be the atom `none'. 
%%
%% The evaluation throws `syntax_error' if
%% `Node' does not represent a well-formed record field
%% specifier.
%%
%% @see analyze_record_attribute/1
%% @see analyze_record_expr/1

-doc """
Returns the label, value-expression, and type of a record field specifier. The
result is a pair `{Label, {Default, Type}}`, if `Node` represents "`Label`",
"`Label = Default`", "`Label :: Type`", or "`Label = Default :: Type`". If the
field has no value-expression, the value for `Default` will be the atom `none`.
If the field has no type, the value for `Type` will be the atom `none`.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
record field specifier.

_See also: _`analyze_record_attribute/1`, `analyze_record_expr/1`.
""".
-spec analyze_record_field(syntaxTree()) -> field().

analyze_record_field(Node) ->
    case erl_syntax:type(Node) of
        record_field ->
            A = erl_syntax:record_field_name(Node),
            case erl_syntax:type(A) of
                atom ->
                    T = erl_syntax:record_field_value(Node),
                    {erl_syntax:atom_value(A), {T, none}};
                _ ->
                    throw(syntax_error)
            end;
        typed_record_field ->
            F = erl_syntax:typed_record_field_body(Node),
            {N, {V, _none}} = analyze_record_field(F),
            T = erl_syntax:typed_record_field_type(Node),
            {N, {V, T}};
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_file_attribute(Node::syntaxTree()) ->
%%           {string(), integer()}
%%
%% @doc Returns the file name and line number of a `file'
%% attribute. The result is the pair `{File, Line}' if
%% `Node' represents "`-file(File, Line).'".
%%
%% The evaluation throws `syntax_error' if
%% `Node' does not represent a well-formed `file'
%% attribute.
%%
%% @see analyze_attribute/1

-doc """
Returns the file name and line number of a `file` attribute. The result is the
pair `{File, Line}` if `Node` represents "`-file(File, Line).`".

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
`file` attribute.

_See also: _`analyze_attribute/1`.
""".
-spec analyze_file_attribute(syntaxTree()) -> {string(), integer()}.

analyze_file_attribute(Node) ->
    case erl_syntax:type(Node) of
        attribute ->
            case erl_syntax:attribute_arguments(Node) of
                [F, N] ->
                    case (erl_syntax:type(F) =:= string)
                        and (erl_syntax:type(N) =:= integer) of
                        true ->
                            {erl_syntax:string_value(F),
                             erl_syntax:integer_value(N)};
                        false ->
                            throw(syntax_error)
                    end;
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_function(Node::syntaxTree()) -> {atom(), integer()}
%%
%% @doc Returns the name and arity of a function definition. The result
%% is a pair `{Name, A}' if `Node' represents a
%% function definition "`Name(P_1, ..., P_A) ->
%% ...'".
%%
%% The evaluation throws `syntax_error' if
%% `Node' does not represent a well-formed function
%% definition.

-doc """
Returns the name and arity of a function definition. The result is a pair
`{Name, A}` if `Node` represents a function definition
"`Name(P_1, ..., P_A) -> ...`".

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
function definition.
""".
-spec analyze_function(syntaxTree()) -> {atom(), arity()}.

analyze_function(Node) ->
    case erl_syntax:type(Node) of
        function ->
            N = erl_syntax:function_name(Node),
            case erl_syntax:type(N) of
                atom ->
                    {erl_syntax:atom_value(N),
                     erl_syntax:function_arity(Node)};
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_implicit_fun(Node::syntaxTree()) -> FunctionName
%%
%%          FunctionName = atom() | {atom(), integer()}
%%                       | {ModuleName, FunctionName}
%%          ModuleName = atom()
%%      
%% @doc Returns the name of an implicit fun expression "`fun
%% F'". The result is a representation of the function
%% name `F'. (Cf. `analyze_function_name/1'.)
%%
%% The evaluation throws `syntax_error' if
%% `Node' does not represent a well-formed implicit fun.
%%
%% @see analyze_function_name/1

-doc """
Returns the name of an implicit fun expression "`fun F`". The result is a
representation of the function name `F`. (Cf.
[`analyze_function_name/1`](`analyze_function_name/1`).)

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
implicit fun.

_See also: _`analyze_function_name/1`.
""".
-spec analyze_implicit_fun(syntaxTree()) -> functionName().

analyze_implicit_fun(Node) ->
    case erl_syntax:type(Node) of
        implicit_fun ->
            analyze_function_name(erl_syntax:implicit_fun_name(Node));
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_application(Node::syntaxTree()) -> FunctionName | Arity
%%
%%          FunctionName = {atom(), Arity}
%%                       | {ModuleName, FunctionName}
%%          Arity = integer()
%%          ModuleName = atom()
%%
%% @doc Returns the name of a called function. The result is a
%% representation of the name of the applied function `F/A',
%% if `Node' represents a function application
%% "`F(X_1, ..., X_A)'". If the
%% function is not explicitly named (i.e., `F' is given by
%% some expression), only the arity `A' is returned.
%%
%% The evaluation throws `syntax_error' if `Node' does not represent a
%% well-formed application expression.
%%
%% @see analyze_function_name/1

-type appFunName() :: {atom(), arity()} | {atom(), {atom(), arity()}}.

-doc """
Returns the name of a called function. The result is a representation of the
name of the applied function `F/A`, if `Node` represents a function application
"`F(X_1, ..., X_A)`". If the function is not explicitly named (i.e., `F` is
given by some expression), only the arity `A` is returned.

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
application expression.

_See also: _`analyze_function_name/1`.
""".
-spec analyze_application(syntaxTree()) -> appFunName() | arity().

analyze_application(Node) ->
    case erl_syntax:type(Node) of
        application ->
            A = length(erl_syntax:application_arguments(Node)),
            F = erl_syntax:application_operator(Node),
            case catch {ok, analyze_function_name(F)} of
                syntax_error ->
                    A;
                {ok, N} ->
                    append_arity(A, N);
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec analyze_type_application(Node::syntaxTree()) -> TypeName
%%
%%          TypeName = {atom(), integer()}
%%                   | {ModuleName, {atom(), integer()}}
%%          ModuleName = atom()
%%
%% @doc Returns the name of a used type. The result is a
%% representation of the name of the used pre-defined or local type `N/A',
%% if `Node' represents a local (user) type application
%% "`N(T_1, ..., T_A)'", or
%% a representation of the name of the used remote type `M:N/A'
%% if `Node' represents a remote user type application
%% "`M:N(T_1, ..., T_A)'".
%%
%% The evaluation throws `syntax_error' if `Node' does not represent a
%% well-formed (user) type application expression.
%%
%% @see analyze_type_name/1

-type typeName() :: atom() | {module(), {atom(), arity()}} | {atom(), arity()}.

-doc """
Returns the name of a used type. The result is a representation of the name of
the used pre-defined or local type `N/A`, if `Node` represents a local (user)
type application "`N(T_1, ..., T_A)`", or a representation of the name of the
used remote type `M:N/A` if `Node` represents a remote user type application
"`M:N(T_1, ..., T_A)`".

The evaluation throws `syntax_error` if `Node` does not represent a well-formed
(user) type application expression.

_See also: _`analyze_type_name/1`.
""".
-spec analyze_type_application(syntaxTree()) -> typeName().

analyze_type_application(Node) ->
    case erl_syntax:type(Node) of
        type_application ->
            A = length(erl_syntax:type_application_arguments(Node)),
            N = erl_syntax:type_application_name(Node),
            case catch {ok, analyze_type_name(N)} of
                {ok, TypeName} ->
                    append_arity(A, TypeName);
                _ ->
                    throw(syntax_error)
            end;
        user_type_application ->
            A = length(erl_syntax:user_type_application_arguments(Node)),
            N = erl_syntax:user_type_application_name(Node),
            case catch {ok, analyze_type_name(N)} of
                {ok, TypeName} ->
                    append_arity(A, TypeName);
                _ ->
                    throw(syntax_error)
            end;
        _ ->
            throw(syntax_error)
    end.


%% =====================================================================
%% @spec function_name_expansions(Names::[Name]) -> [{ShortName, Name}]
%%
%%          Name = ShortName | {atom(), Name}
%%          ShortName = atom() | {atom(), integer()}
%%
%% @doc Creates a mapping from corresponding short names to full
%% function names. Names are represented by nested tuples of atoms and
%% integers (cf. `analyze_function_name/1'). The result is a
%% list containing a pair `{ShortName, Name}' for each
%% element `Name' in the given list, where the corresponding
%% `ShortName' is the rightmost-innermost part of
%% `Name'. The list thus represents a finite mapping from
%% unqualified names to the corresponding qualified names.
%%
%% Note: the resulting list can contain more than one tuple
%% `{ShortName, Name}' for the same `ShortName',
%% possibly with different values for `Name', depending on
%% the given list.
%%
%% @see analyze_function_name/1

-type shortname() :: atom() | {atom(), arity()}.
-type name()      :: shortname() | {atom(), shortname()}.

-doc """
Creates a mapping from corresponding short names to full function names. Names
are represented by nested tuples of atoms and integers (cf.
[`analyze_function_name/1`](`analyze_function_name/1`)). The result is a list
containing a pair `{ShortName, Name}` for each element `Name` in the given list,
where the corresponding `ShortName` is the rightmost-innermost part of `Name`.
The list thus represents a finite mapping from unqualified names to the
corresponding qualified names.

Note: the resulting list can contain more than one tuple `{ShortName, Name}` for
the same `ShortName`, possibly with different values for `Name`, depending on
the given list.

_See also: _`analyze_function_name/1`.
""".
-spec function_name_expansions([name()]) -> [{shortname(), name()}].

function_name_expansions(Fs) ->
    function_name_expansions(Fs, []).

function_name_expansions([F | Fs], Ack) ->
    function_name_expansions(Fs,
                             function_name_expansions(F, F, Ack));
function_name_expansions([], Ack) ->
    Ack.

function_name_expansions({A, N}, Name, Ack) when is_integer(N) ->
    [{{A, N}, Name} | Ack];
function_name_expansions({_, N}, Name, Ack) ->
    function_name_expansions(N, Name,  Ack);
function_name_expansions(A, Name, Ack) ->
    [{A, Name} | Ack].


%% =====================================================================
%% @spec strip_comments(Tree::syntaxTree()) -> syntaxTree()
%%
%% @doc Removes all comments from all nodes of a syntax tree. All other
%% attributes (such as position information) remain unchanged.
%% Standalone comments in form lists are removed; any other standalone
%% comments are changed into null-comments (no text, no indentation).

-doc """
Removes all comments from all nodes of a syntax tree. All other attributes (such
as position information) remain unchanged. Standalone comments in form lists are
removed; any other standalone comments are changed into null-comments (no text,
no indentation).
""".
-spec strip_comments(syntaxTree()) -> syntaxTree().

strip_comments(Tree) ->
    map(fun strip_comments_1/1, Tree).

strip_comments_1(T) ->
    case erl_syntax:type(T) of
	form_list ->
	    Es = erl_syntax:form_list_elements(T),
	    Es1 = [E || E <- Es, erl_syntax:type(E) /= comment],
	    T1 = erl_syntax:copy_attrs(T, erl_syntax:form_list(Es1)),
	    erl_syntax:remove_comments(T1);
	comment ->
	    erl_syntax:comment([]);
	_ ->
	    erl_syntax:remove_comments(T)
    end.

%% =====================================================================
%% @spec to_comment(Tree) -> syntaxTree()
%% @equiv to_comment(Tree, "% ")

-doc """
Equivalent to [to_comment(Tree, "% ")](`to_comment/2`).
""".
-spec to_comment(syntaxTree()) -> syntaxTree().

to_comment(Tree) ->
    to_comment(Tree, "% ").

%% =====================================================================
%% @spec to_comment(Tree::syntaxTree(), Prefix::string()) ->
%%           syntaxTree()
%%
%% @doc Equivalent to `to_comment(Tree, Prefix, F)' for a
%% default formatting function `F'. The default
%% `F' simply calls `erl_prettypr:format/1'.
%%
%% @see to_comment/3
%% @see erl_prettypr:format/1

-doc """
Equivalent to [`to_comment(Tree, Prefix, F)`](`to_comment/3`) for a default
formatting function `F`. The default `F` simply calls `erl_prettypr:format/1`.

_See also: _`to_comment/3`, `erl_prettypr:format/1`.
""".
-spec to_comment(syntaxTree(), string()) -> syntaxTree().

to_comment(Tree, Prefix) ->
    F = fun (T) -> erl_prettypr:format(T) end,
    to_comment(Tree, Prefix, F).

%% =====================================================================
%% @spec to_comment(Tree::syntaxTree(), Prefix::string(), Printer) ->
%%           syntaxTree()
%%
%%          Printer = (syntaxTree()) -> string()
%%
%% @doc Transforms a syntax tree into an abstract comment. The lines of
%% the comment contain the text for `Node', as produced by
%% the given `Printer' function. Each line of the comment is
%% prefixed by the string `Prefix' (this does not include the
%% initial "`%'" character of the comment line).
%%
%% For example, the result of
%% `to_comment(erl_syntax:abstract([a,b,c]))' represents
%% <pre>
%%         %% [a,b,c]</pre>
%% (cf. `to_comment/1').
%%
%% Note: the text returned by the formatting function will be split
%% automatically into separate comment lines at each line break. No
%% extra work is needed.
%%
%% @see to_comment/1
%% @see to_comment/2

-doc """
Transforms a syntax tree into an abstract comment. The lines of the comment
contain the text for `Node`, as produced by the given `Printer` function. Each
line of the comment is prefixed by the string `Prefix` (this does not include
the initial "`%`" character of the comment line).

For example, the result of
[`to_comment(erl_syntax:abstract([a,b,c]))`](`to_comment/1`) represents

```text
          %% [a,b,c]
```

(cf. [`to_comment/1`](`to_comment/1`)).

Note: the text returned by the formatting function will be split automatically
into separate comment lines at each line break. No extra work is needed.

_See also: _`to_comment/1`, `to_comment/2`.
""".
-spec to_comment(syntaxTree(), string(),
		 fun((syntaxTree()) -> string())) ->
        syntaxTree().

to_comment(Tree, Prefix, F) ->
    erl_syntax:comment(split_lines(F(Tree), Prefix)).


%% =====================================================================
%% @spec limit(Tree, Depth) -> syntaxTree()
%%
%% @doc Equivalent to `limit(Tree, Depth, Text)' using the
%% text `"..."' as default replacement.
%%
%% @see limit/3
%% @see erl_syntax:text/1

-doc """
Equivalent to [`limit(Tree, Depth, Text)`](`limit/3`) using the text `"..."` as
default replacement.

_See also: _`limit/3`, `erl_syntax:text/1`.
""".
-spec limit(syntaxTree(), integer()) -> syntaxTree().

limit(Tree, Depth) ->
    limit(Tree, Depth, erl_syntax:text("...")).

%% =====================================================================
%% @spec limit(Tree::syntaxTree(), Depth::integer(),
%%             Node::syntaxTree()) -> syntaxTree()
%%
%% @doc Limits a syntax tree to a specified depth. Replaces all non-leaf
%% subtrees in `Tree' at the given `Depth' by
%% `Node'. If `Depth' is negative, the result is
%% always `Node', even if `Tree' has no subtrees.
%%
%% When a group of subtrees (as e.g., the argument list of an
%% `application' node) is at the specified depth, and there
%% are two or more subtrees in the group, these will be collectively
%% replaced by `Node' even if they are leaf nodes. Groups of
%% subtrees that are above the specified depth will be limited in size,
%% as if each subsequent tree in the group were one level deeper than
%% the previous. E.g., if `Tree' represents a list of
%% integers "`[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]'", the result
%% of `limit(Tree, 5)' will represent `[1, 2, 3, 4,
%% ...]'.
%%
%% The resulting syntax tree is typically only useful for
%% pretty-printing or similar visual formatting.
%%
%% @see limit/2

-doc """
Limits a syntax tree to a specified depth. Replaces all non-leaf subtrees in
`Tree` at the given `Depth` by `Node`. If `Depth` is negative, the result is
always `Node`, even if `Tree` has no subtrees.

When a group of subtrees (as e.g., the argument list of an `application` node)
is at the specified depth, and there are two or more subtrees in the group,
these will be collectively replaced by `Node` even if they are leaf nodes.
Groups of subtrees that are above the specified depth will be limited in size,
as if each subsequent tree in the group were one level deeper than the previous.
E.g., if `Tree` represents a list of integers
"`[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]`", the result of [`limit(Tree, 5)`](`limit/2`)
will represent `[1, 2, 3, 4, ...]`.

The resulting syntax tree is typically only useful for pretty-printing or
similar visual formatting.

_See also: _`limit/2`.
""".
-spec limit(syntaxTree(), integer(), syntaxTree()) ->
        syntaxTree().

limit(_Tree, Depth, Node) when Depth < 0 ->
    Node;
limit(Tree, Depth, Node) ->
    limit_1(Tree, Depth, Node).

limit_1(Tree, Depth, Node) ->
    %% Depth is nonnegative here.
    case erl_syntax:subtrees(Tree) of
        [] ->
            if Depth > 0 ->
                    Tree;
               true ->
                    case is_simple_leaf(Tree) of
                        true ->
                            Tree;
                        false ->
                            Node
                    end
            end;
        Gs ->
            if Depth > 1 ->
                    Gs1 = [[limit_1(T, Depth - 1, Node)
                            || T <- limit_list(G, Depth, Node)]
                           || G <- Gs],
                    rewrite(Tree,
                            erl_syntax:make_tree(erl_syntax:type(Tree),
                                                 Gs1));
               Depth =:= 0 ->
                    %% Depth is zero, and this is not a leaf node
                    %% so we always replace it.
                    Node;
               true ->
                    %% Depth is 1, so all subtrees are to be cut.
                    %% This is done groupwise.
                    Gs1 = [cut_group(G, Node) || G <- Gs],
                    rewrite(Tree,
                            erl_syntax:make_tree(erl_syntax:type(Tree),
                                                 Gs1))
            end
    end.

cut_group([], _Node) ->
    [];
cut_group([T], Node) ->
    %% Only if the group contains a single subtree do we try to
    %% preserve it if suitable.
    [limit_1(T, 0, Node)];
cut_group(_Ts, Node) ->
    [Node].

is_simple_leaf(Tree) ->
    case erl_syntax:type(Tree) of
        atom -> true;
        char -> true;
        float -> true;
        integer -> true;
        nil -> true;
        operator -> true;
        tuple -> true;
        underscore -> true;
        variable -> true;
        _ -> false
    end.

%% If list has more than N elements, take the N - 1 first and
%% append Node; otherwise return list as is.

limit_list(Ts, N, Node) ->
    if length(Ts) > N ->
            limit_list_1(Ts, N - 1, Node);
       true ->
            Ts
    end.

limit_list_1([T | Ts], N, Node) ->
    if N > 0 ->
            [T | limit_list_1(Ts, N - 1, Node)];
       true ->
            [Node]
    end;
limit_list_1([], _N, _Node) ->
    [].


%% =====================================================================
%% Utility functions

rewrite(Tree, Tree1) ->
    erl_syntax:copy_attrs(Tree, Tree1).

module_name_to_atom(M) ->
    case erl_syntax:type(M) of
	atom ->
	    erl_syntax:atom_value(M);
	_ ->
	    throw(syntax_error)
    end.

%% This splits lines at line terminators and expands tab characters to
%% spaces. The width of a tab is assumed to be 8.

% split_lines(Cs) ->
%     split_lines(Cs, "").

split_lines(Cs, Prefix) ->
    split_lines(Cs, Prefix, 0).

split_lines(Cs, Prefix, N) ->
    lists:reverse(split_lines(Cs, N, [], [], Prefix)).

split_lines([$\r, $\n | Cs], _N, Cs1, Ls, Prefix) ->
    split_lines_1(Cs, Cs1, Ls, Prefix);
split_lines([$\r | Cs], _N, Cs1, Ls, Prefix) ->
    split_lines_1(Cs, Cs1, Ls, Prefix);
split_lines([$\n | Cs], _N, Cs1, Ls, Prefix) ->
    split_lines_1(Cs, Cs1, Ls, Prefix);
split_lines([$\t | Cs], N, Cs1, Ls, Prefix) ->
    split_lines(Cs, 0, push(8 - (N rem 8), $\040, Cs1), Ls,
                Prefix);
split_lines([C | Cs], N, Cs1, Ls, Prefix) ->
    split_lines(Cs, N + 1, [C | Cs1], Ls, Prefix);
split_lines([], _, [], Ls, _) ->
    Ls;
split_lines([], _N, Cs, Ls, Prefix) ->
    [Prefix ++ lists:reverse(Cs) | Ls].

split_lines_1(Cs, Cs1, Ls, Prefix) ->
    split_lines(Cs, 0, [], [Prefix ++ lists:reverse(Cs1) | Ls],
                Prefix).

push(N, C, Cs) when N > 0 ->
    push(N - 1, C, [C | Cs]);
push(0, _, Cs) ->
    Cs.

