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author | Sverker Eriksson <[email protected]> | 2017-08-30 20:55:08 +0200 |
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committer | Sverker Eriksson <[email protected]> | 2017-08-30 20:55:08 +0200 |
commit | 7c67bbddb53c364086f66260701bc54a61c9659c (patch) | |
tree | 92ab0d4b91d5e2f6e7a3f9d61ea25089e8a71fe0 /lib/syntax_tools/src/merl.erl | |
parent | 97dc5e7f396129222419811c173edc7fa767b0f8 (diff) | |
parent | 3b7a6ffddc819bf305353a593904cea9e932e7dc (diff) | |
download | otp-7c67bbddb53c364086f66260701bc54a61c9659c.tar.gz otp-7c67bbddb53c364086f66260701bc54a61c9659c.tar.bz2 otp-7c67bbddb53c364086f66260701bc54a61c9659c.zip |
Merge tag 'OTP-19.0' into sverker/19/binary_to_atom-utf8-crash/ERL-474/OTP-14590
Diffstat (limited to 'lib/syntax_tools/src/merl.erl')
-rw-r--r-- | lib/syntax_tools/src/merl.erl | 1240 |
1 files changed, 1240 insertions, 0 deletions
diff --git a/lib/syntax_tools/src/merl.erl b/lib/syntax_tools/src/merl.erl new file mode 100644 index 0000000000..163ce48bbc --- /dev/null +++ b/lib/syntax_tools/src/merl.erl @@ -0,0 +1,1240 @@ +%% --------------------------------------------------------------------- +%% 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. +%% +%% Note: EDoc uses @@ and @} as escape sequences, so in the doc text below, +%% `@@' must be written `@@@@' and `@}' must be written `@@}'. +%% +%% @author Richard Carlsson <[email protected]> +%% @copyright 2010-2015 Richard Carlsson +%% +%% @doc Metaprogramming in Erlang. +%% Merl is a more user friendly interface to the `erl_syntax' module, making +%% it easy both to build new ASTs from scratch and to +%% match and decompose existing ASTs. For details that are outside the scope +%% of Merl itself, please see the documentation of {@link erl_syntax}. +%% +%% == Quick start == +%% +%% To enable the full power of Merl, your module needs to include the Merl +%% header file: +%% ```-include_lib("syntax_tools/include/merl.hrl").''' +%% +%% Then, you can use the `?Q(Text)' macros in your code to create ASTs or match +%% on existing ASTs. For example: +%% ```Tuple = ?Q("{foo, 42}"), +%% ?Q("{foo, _@Number}") = Tuple, +%% Call = ?Q("foo:bar(_@Number)")''' +%% +%% Calling `merl:print(Call)' will then print the following code: +%% ```foo:bar(42)''' +%% +%% The `?Q' macros turn the quoted code fragments into ASTs, and lifts +%% metavariables such as `_@Tuple' and `_@Number' to the level of your Erlang +%% code, so you can use the corresponding Erlang variables `Tuple' and `Number' +%% directly. This is the most straightforward way to use Merl, and in many +%% cases it's all you need. +%% +%% You can even write case switches using `?Q' macros as patterns. For example: +%% ```case AST of +%% ?Q("{foo, _@Foo}") -> handle(Foo); +%% ?Q("{bar, _@Bar}") when erl_syntax:is_integer(Bar) -> handle(Bar); +%% _ -> handle_default() +%% end''' +%% +%% These case switches only allow `?Q(...)' or `_' as clause patterns, and the +%% guards may contain any expressions, not just Erlang guard expressions. +%% +%% If the macro `MERL_NO_TRANSFORM' is defined before the `merl.hrl' header +%% file is included, the parse transform used by Merl will be disabled, and in +%% that case, the match expressions `?Q(...) = ...', case switches using +%% `?Q(...)' patterns, and automatic metavariables like `_@Tuple' cannot be +%% used in your code, but the Merl macros and functions still work. To do +%% metavariable substitution, you need to use the `?Q(Text, Map)' macro, e.g.: +%% ```Tuple = ?Q("{foo, _@bar, _@baz}", [{bar, Bar}, {baz,Baz}])''' +%% +%% The text given to a `?Q(Text)' macro can be either a single string, or a +%% list of strings. The latter is useful when you need to split a long +%% expression over multiple lines, e.g.: +%% ```?Q(["case _@Expr of", +%% " {foo, X} -> f(X);", +%% " {bar, X} -> g(X)", +%% " _ -> h(X)" +%% "end"])''' +%% If there is a syntax error somewhere in the text (like the missing semicolon +%% in the second clause above) this allows Merl to generate an error message +%% pointing to the exact line in your source code. (Just remember to +%% comma-separate the strings in the list, otherwise Erlang will concatenate +%% the string fragments as if they were a single string.) +%% +%% == Metavariable syntax == +%% +%% There are several ways to write a metavariable in your quoted code: +%% <ul> +%% <li>Atoms starting with `@', for example `` '@foo' '' or `` '@Foo' ''</li> +%% <li>Variables starting with `_@', for example `_@bar' or `_@Bar'</li> +%% <li>Strings starting with ``"'@'', for example ``"'@File"''</li> +%% <li>Integers starting with 909, for example `9091' or `909123'</li> +%% </ul> +%% Following the prefix, one or more `_' or `0' characters may be used to +%% indicate "lifting" of the variable one or more levels, and after that, a `@' +%% or `9' character indicates a glob metavariable (matching zero or more +%% elements in a sequence) rather than a normal metavariable. For example: +%% <ul> +%% <li>`` '@_foo' '' is lifted one level, and `_@__foo' is lifted two +%% levels</li> +%% <li>`_@@@@bar' is a glob variable, and `_@_@bar' is a lifted glob +%% variable</li> +%% <li>`90901' is a lifted variable,`90991' is a glob variable, and `9090091' +%% is a glob variable lifted two levels</li> +%% </ul> +%% (Note that the last character in the name is never considered to be a lift +%% or glob marker, hence, `_@__' and `90900' are only lifted one level, not +%% two. Also note that globs only matter for matching; when doing +%% substitutions, a non-glob variable can be used to inject a sequence of +%% elements, and vice versa.) +%% +%% If the name after the prefix and any lift and glob markers is `_' or `0', +%% the variable is treated as an anonymous catch-all pattern in matches. For +%% example, `_@_', `_@@@@_', `_@__', or even `_@__@_'. +%% +%% Finally, if the name without any prefixes or lift/glob markers begins with +%% an uppercase character, as in `_@Foo' or `_@_@Foo', it will become a +%% variable on the Erlang level, and can be used to easily deconstruct and +%% construct syntax trees: +%% ```case Input of +%% ?Q("{foo, _@Number}") -> ?Q("foo:bar(_@Number)"); +%% ...''' +%% We refer to these as "automatic metavariables". If in addition the name ends +%% with `@', as in `_@Foo@', the value of the variable as an Erlang term will +%% be automatically converted to the corresponding abstract syntax tree when +%% used to construct a larger tree. For example, in: +%% ```Bar = {bar, 42}, +%% Foo = ?Q("{foo, _@Bar@@}")''' +%% (where Bar is just some term, not a syntax tree) the result `Foo' will be a +%% syntax tree representing `{foo, {bar, 42}}'. This avoids the need for +%% temporary variables in order to inject data, as in +%% ```TmpBar = erl_syntax:abstract(Bar), +%% Foo = ?Q("{foo, _@TmpBar}")''' +%% +%% If the context requires an integer rather than a variable, an atom, or a +%% string, you cannot use the uppercase convention to mark an automatic +%% metavariable. Instead, if the integer (without the `909'-prefix and +%% lift/glob markers) ends in a `9', the integer will become an Erlang-level +%% variable prefixed with `Q', and if it ends with `99' it will also be +%% automatically abstracted. For example, the following will increment the +%% arity of the exported function f: +%% ```case Form of +%% ?Q("-export([f/90919]).") -> +%% Q2 = erl_syntax:concrete(Q1) + 1, +%% ?Q("-export([f/909299])."); +%% ...''' +%% +%% == When to use the various forms of metavariables == +%% +%% Merl can only parse a fragment of text if it follows the basic syntactical +%% rules of Erlang. In most places, a normal Erlang variable can be used as +%% metavariable, for example: +%% ```?Q("f(_@Arg)") = Expr''' +%% but if you want to match on something like the name of a function, you have +%% to use an atom as metavariable: +%% ```?Q("'@Name'() -> _@@@@_." = Function''' +%% (note the anonymous glob variable `_@@@@_' to ignore the function body). +%% +%% In some contexts, only a string or an integer is allowed. For example, the +%% directive `-file(Name, Line)' requires that `Name' is a string literal and +%% `Line' an integer literal: +%% +%% ```?Q("-file(\"'@File\", 9090).") = ?Q("-file(\"foo.erl\", 42).")).''' +%% This will extract the string literal `"foo.erl"' into the variable `Foo'. +%% Note the use of the anonymous variable `9090' to ignore the line number. To +%% match and also bind a metavariable that must be an integer literal, we can +%% use the convention of ending the integer with a 9, turning it into a +%% Q-prefixed variable on the Erlang level (see the previous section). +%% +%% === Globs === +%% +%% Whenever you want to match out a number of elements in a sequence (zero or +%% more) rather than a fixed set of elements, you need to use a glob. For +%% example: +%% ```?Q("{_@@@@Elements}") = ?Q({a, b, c})''' +%% will bind Elements to the list of individual syntax trees representing the +%% atoms `a', `b', and `c'. This can also be used with static prefix and suffix +%% elements in the sequence. For example: +%% ```?Q("{a, b, _@@@@Elements}") = ?Q({a, b, c, d})''' +%% will bind Elements to the list of the `c' and `d' subtrees, and +%% ```?Q("{_@@@@Elements, c, d}") = ?Q({a, b, c, d})''' +%% will bind Elements to the list of the `a' and `b' subtrees. You can even use +%% plain metavariables in the prefix or suffix: +%% ```?Q("{_@First, _@@@@Rest}") = ?Q({a, b, c})''' +%% or +%% ```?Q("{_@@@@_, _@Last}") = ?Q({a, b, c})''' +%% (ignoring all but the last element). You cannot however have two globs as +%% part of the same sequence. +%% +%% === Lifted metavariables === +%% +%% In some cases, the Erlang syntax rules make it impossible to place a +%% metavariable directly where you would like it. For example, you cannot +%% write: +%% ```?Q("-export([_@@@@Name]).")''' +%% to match out all name/arity pairs in the export list, or to insert a list of +%% exports in a declaration, because the Erlang parser only allows elements on +%% the form `A/I' (where `A' is an atom and `I' an integer) in the export list. +%% A variable like the above is not allowed, but neither is a single atom or +%% integer, so `` '@@@@Name' '' or `909919' wouldn't work either. +%% +%% What you have to do in such cases is to write your metavariable in a +%% syntactically valid position, and use lifting markers to denote where it +%% should really apply, as in: +%% ```?Q("-export(['@@_@@Name'/0]).")''' +%% This causes the variable to be lifted (after parsing) to the next higher +%% level in the syntax tree, replacing that entire subtree. In this case, the +%% `` '@@_@@Name'/0 '' will be replaced with `` '@@@@Name' '', and the ``/0'' +%% part was just used as dummy notation and will be discarded. +%% +%% You may even need to apply lifting more than once. To match the entire +%% export list as a single syntax tree, you can write: +%% ```?Q("-export(['@@__Name'/0]).")''' +%% using two underscores, but with no glob marker this time. This will make the +%% entire ``['@@__Name'/0]'' part be replaced with `` '@@Name' ''. +%% +%% Sometimes, the tree structure of a code fragment isn't very obvious, and +%% parts of the structure may be invisible when printed as source code. For +%% instance, a simple function definition like the following: +%% ```zero() -> 0.''' +%% consists of the name (the atom `zero'), and a list of clauses containing the +%% single clause `() -> 0'. The clause consists of an argument list (empty), a +%% guard (empty), and a body (which is always a list of expressions) containing +%% the single expression `0'. This means that to match out the name and the +%% list of clauses of any function, you'll need to use a pattern like +%% ``?Q("'@Name'() -> _@_@Body.")'', using a dummy clause whose body is a glob +%% lifted one level. +%% +%% To visualize the structure of a syntax tree, you can use the function +%% `merl:show(T)', which prints a summary. For example, entering +%% ```merl:show(merl:quote("inc(X, Y) when Y > 0 -> X + Y."))''' +%% in the Erlang shell will print the following (where the `+' signs separate +%% groups of subtrees on the same level): +%% ```function: inc(X, Y) when ... -> X + Y. +%% atom: inc +%% + +%% clause: (X, Y) when ... -> X + Y +%% variable: X +%% variable: Y +%% + +%% disjunction: Y > 0 +%% conjunction: Y > 0 +%% infix_expr: Y > 0 +%% variable: Y +%% + +%% operator: > +%% + +%% integer: 0 +%% + +%% infix_expr: X + Y +%% variable: X +%% + +%% operator: + +%% + +%% variable: Y''' +%% +%% This shows another important non-obvious case: a clause guard, even if it's +%% as simple as `Y > 0', always consists of a single disjunction of one or more +%% conjunctions of tests, much like a tuple of tuples. Thus: +%% <ul> +%% <li>``"when _@Guard ->"'' will only match a guard with exactly one +%% test</li> +%% <li>``"when _@@@@Guard ->"'' will match a guard with one or more +%% comma-separated tests (but no semicolons), binding `Guard' to the list +%% of tests</li> +%% <li>``"when _@_Guard ->"'' will match just like the previous pattern, but +%% binds `Guard' to the conjunction subtree</li> +%% <li>``"when _@_@Guard ->"'' will match an arbitrary nonempty guard, +%% binding `Guard' to the list of conjunction subtrees</li> +%% <li>``"when _@__Guard ->"'' will match like the previous pattern, but +%% binds `Guard' to the whole disjunction subtree</li> +%% <li>and finally, ``"when _@__@Guard ->"'' will match any clause, +%% binding `Guard' to `[]' if the guard is empty and to `[Disjunction]' +%% otherwise</li> +%% </ul> +%% +%% Thus, the following pattern matches all possible clauses: +%% ```"(_@@Args) when _@__@Guard -> _@@Body"''' +%% @end + +-module(merl). + +-export([term/1, var/1, print/1, show/1]). + +-export([quote/1, quote/2, qquote/2, qquote/3]). + +-export([template/1, tree/1, subst/2, tsubst/2, alpha/2, match/2, switch/2]). + +-export([template_vars/1, meta_template/1]). + +-export([compile/1, compile/2, compile_and_load/1, compile_and_load/2]). + +%% NOTE: this module may not include merl.hrl! + +-type tree() :: erl_syntax:syntaxTree(). + +-type tree_or_trees() :: tree() | [tree()]. + +-type pattern() :: tree() | template(). + +-type pattern_or_patterns() :: pattern() | [pattern()]. + +-type env() :: [{Key::id(), pattern_or_patterns()}]. + +-type id() :: atom() | integer(). + +%% A list of strings or binaries is assumed to represent individual lines, +%% while a flat string or binary represents source code containing newlines. +-type text() :: string() | binary() | [string()] | [binary()]. + +-type location() :: erl_anno:location(). + + +%% ------------------------------------------------------------------------ +%% Compiling and loading code directly to memory + +%% @equiv compile(Code, []) +compile(Code) -> + compile(Code, []). + +%% @doc Compile a syntax tree or list of syntax trees representing a module +%% into a binary BEAM object. +%% @see compile_and_load/2 +%% @see compile/1 +compile(Code, Options) when not is_list(Code)-> + case type(Code) of + form_list -> compile(erl_syntax:form_list_elements(Code)); + _ -> compile([Code], Options) + end; +compile(Code, Options0) when is_list(Options0) -> + Forms = [erl_syntax:revert(F) || F <- Code], + Options = [verbose, report_errors, report_warnings, binary | Options0], + compile:noenv_forms(Forms, Options). + + +%% @equiv compile_and_load(Code, []) +compile_and_load(Code) -> + compile_and_load(Code, []). + +%% @doc Compile a syntax tree or list of syntax trees representing a module +%% and load the resulting module into memory. +%% @see compile/2 +%% @see compile_and_load/1 +compile_and_load(Code, Options) -> + case compile(Code, Options) of + {ok, ModuleName, Binary} -> + _ = code:load_binary(ModuleName, "", Binary), + {ok, Binary}; + Other -> Other + end. + + +%% ------------------------------------------------------------------------ +%% Utility functions + + +-spec var(atom()) -> tree(). + +%% @doc Create a variable. + +var(Name) -> + erl_syntax:variable(Name). + + +-spec term(term()) -> tree(). + +%% @doc Create a syntax tree for a constant term. + +term(Term) -> + erl_syntax:abstract(Term). + + +%% @doc Pretty-print a syntax tree or template to the standard output. This +%% is a utility function for development and debugging. + +print(Ts) when is_list(Ts) -> + lists:foreach(fun print/1, Ts); +print(T) -> + io:put_chars(erl_prettypr:format(tree(T))), + io:nl(). + +%% @doc Print the structure of a syntax tree or template to the standard +%% output. This is a utility function for development and debugging. + +show(Ts) when is_list(Ts) -> + lists:foreach(fun show/1, Ts); +show(T) -> + io:put_chars(pp(tree(T), 0)), + io:nl(). + +pp(T, I) -> + [lists:duplicate(I, $\s), + limit(lists:flatten([atom_to_list(type(T)), ": ", + erl_prettypr:format(erl_syntax_lib:limit(T,3))]), + 79-I), + $\n, + pp_1(lists:filter(fun (X) -> X =/= [] end, subtrees(T)), I+2) + ]. + +pp_1([G], I) -> + pp_2(G, I); +pp_1([G | Gs], I) -> + [pp_2(G, I), lists:duplicate(I, $\s), "+\n" | pp_1(Gs, I)]; +pp_1([], _I) -> + []. + +pp_2(G, I) -> + [pp(E, I) || E <- G]. + +%% limit string to N characters, stay on a single line and compact whitespace +limit([$\n | Cs], N) -> limit([$\s | Cs], N); +limit([$\r | Cs], N) -> limit([$\s | Cs], N); +limit([$\v | Cs], N) -> limit([$\s | Cs], N); +limit([$\t | Cs], N) -> limit([$\s | Cs], N); +limit([$\s, $\s | Cs], N) -> limit([$\s | Cs], N); +limit([C | Cs], N) when C < 32 -> limit(Cs, N); +limit([C | Cs], N) when N > 3 -> [C | limit(Cs, N-1)]; +limit([_C1, _C2, _C3, _C4 | _Cs], 3) -> "..."; +limit(Cs, 3) -> Cs; +limit([_C1, _C2, _C3 | _], 2) -> ".."; +limit(Cs, 2) -> Cs; +limit([_C1, _C2 | _], 1) -> "."; +limit(Cs, 1) -> Cs; +limit(_, _) -> []. + +%% ------------------------------------------------------------------------ +%% Parsing and instantiating code fragments + + +-spec qquote(Text::text(), Env::env()) -> tree_or_trees(). + +%% @doc Parse text and substitute meta-variables. +%% +%% @equiv qquote(1, Text, Env) + +qquote(Text, Env) -> + qquote(1, Text, Env). + + +-spec qquote(StartPos::location(), Text::text(), Env::env()) -> tree_or_trees(). + +%% @doc Parse text and substitute meta-variables. Takes an initial scanner +%% starting position as first argument. +%% +%% The macro `?Q(Text, Env)' expands to `merl:qquote(?LINE, Text, Env)'. +%% +%% @see quote/2 + +qquote(StartPos, Text, Env) -> + subst(quote(StartPos, Text), Env). + + +-spec quote(Text::text()) -> tree_or_trees(). + +%% @doc Parse text. +%% +%% @equiv quote(1, Text) + +quote(Text) -> + quote(1, Text). + + +-spec quote(StartPos::location(), Text::text()) -> tree_or_trees(). + +%% @doc Parse text. Takes an initial scanner starting position as first +%% argument. +%% +%% The macro `?Q(Text)' expands to `merl:quote(?LINE, Text, Env)'. +%% +%% @see quote/1 + +quote({Line, Col}, Text) + when is_integer(Line), is_integer(Col) -> + quote_1(Line, Col, Text); +quote(StartPos, Text) when is_integer(StartPos) -> + quote_1(StartPos, undefined, Text). + +quote_1(StartLine, StartCol, Text) -> + %% be backwards compatible as far as R12, ignoring any starting column + StartPos = case erlang:system_info(version) of + "5.6" ++ _ -> StartLine; + "5.7" ++ _ -> StartLine; + "5.8" ++ _ -> StartLine; + _ when StartCol =:= undefined -> StartLine; + _ -> {StartLine, StartCol} + end, + FlatText = flatten_text(Text), + {ok, Ts, _} = erl_scan:string(FlatText, StartPos), + merge_comments(StartLine, erl_comment_scan:string(FlatText), parse_1(Ts)). + +parse_1(Ts) -> + %% if dot tokens are present, it is assumed that the text represents + %% complete forms, not dot-terminated expressions or similar + case split_forms(Ts) of + {ok, Fs} -> parse_forms(Fs); + error -> + parse_2(Ts) + end. + +split_forms(Ts) -> + split_forms(Ts, [], []). + +split_forms([{dot,_}=T|Ts], Fs, As) -> + split_forms(Ts, [lists:reverse(As, [T]) | Fs], []); +split_forms([T|Ts], Fs, As) -> + split_forms(Ts, Fs, [T|As]); +split_forms([], Fs, []) -> + {ok, lists:reverse(Fs)}; +split_forms([], [], _) -> + error; % no dot tokens found - not representing form(s) +split_forms([], _, [T|_]) -> + fail("incomplete form after ~p", [T]). + +parse_forms([Ts | Tss]) -> + case erl_parse:parse_form(Ts) of + {ok, Form} -> [Form | parse_forms(Tss)]; + {error, R} -> parse_error(R) + end; +parse_forms([]) -> + []. + +parse_2(Ts) -> + %% one or more comma-separated expressions? + %% (recall that Ts has no dot tokens if we get to this stage) + A = a0(), + case erl_parse:parse_exprs(Ts ++ [{dot,A}]) of + {ok, Exprs} -> Exprs; + {error, E} -> + parse_3(Ts ++ [{'end',A}, {dot,A}], [E]) + end. + +parse_3(Ts, Es) -> + %% try-clause or clauses? + A = a0(), + case erl_parse:parse_exprs([{'try',A}, {atom,A,true}, {'catch',A} | Ts]) of + {ok, [{'try',_,_,_,_,_}=X]} -> + %% get the right kind of qualifiers in the clause patterns + erl_syntax:try_expr_handlers(X); + {error, E} -> + parse_4(Ts, [E|Es]) + end. + +parse_4(Ts, Es) -> + %% fun-clause or clauses? (`(a)' is also a pattern, but `(a,b)' isn't, + %% so fun-clauses must be tried before normal case-clauses + A = a0(), + case erl_parse:parse_exprs([{'fun',A} | Ts]) of + {ok, [{'fun',_,{clauses,Cs}}]} -> Cs; + {error, E} -> + parse_5(Ts, [E|Es]) + end. + +parse_5(Ts, Es) -> + %% case-clause or clauses? + A = a0(), + case erl_parse:parse_exprs([{'case',A}, {atom,A,true}, {'of',A} | Ts]) of + {ok, [{'case',_,_,Cs}]} -> Cs; + {error, E} -> + %% select the best error to report + parse_error(lists:last(lists:sort([E|Es]))) + end. + +-dialyzer({nowarn_function, parse_error/1}). % no local return + +parse_error({L, M, R}) when is_atom(M), is_integer(L) -> + fail("~w: ~s", [L, M:format_error(R)]); +parse_error({{L,C}, M, R}) when is_atom(M), is_integer(L), is_integer(C) -> + fail("~w:~w: ~s", [L,C,M:format_error(R)]); +parse_error({_, M, R}) when is_atom(M) -> + fail(M:format_error(R)); +parse_error(R) -> + fail("unknown parse error: ~p", [R]). + +%% ------------------------------------------------------------------------ +%% Templates, substitution and matching + +%% Leaves are normal syntax trees, and inner nodes are tuples +%% {template,Type,Attrs,Groups} where Groups are lists of lists of nodes. +%% Metavariables are 1-tuples {VarName}, where VarName is an atom or an +%% integer. {'_'} and {0} work as anonymous variables in matching. Glob +%% metavariables are tuples {'*',VarName}, and {'*','_'} and {'*',0} are +%% anonymous globs. + +%% Note that although template() :: tree() | ..., it is implied that these +%% syntax trees are free from metavariables, so pattern() :: tree() | +%% template() is in fact a wider type than template(). + +-type template() :: tree() + | {id()} + | {'*',id()} + | {template, atom(), term(), [[template()]]}. + +-type template_or_templates() :: template() | [template()]. + +-spec template(pattern_or_patterns()) -> template_or_templates(). + +%% @doc Turn a syntax tree or list of trees into a template or templates. +%% Templates can be instantiated or matched against, and reverted back to +%% normal syntax trees using {@link tree/1}. If the input is already a +%% template, it is not modified further. +%% +%% @see subst/2 +%% @see match/2 +%% @see tree/1 + +template(Trees) when is_list(Trees) -> + [template_0(T) || T <- Trees]; +template(Tree) -> + template_0(Tree). + +template_0({template, _, _, _}=Template) -> Template; +template_0({'*',_}=Template) -> Template; +template_0({_}=Template) -> Template; +template_0(Tree) -> + case template_1(Tree) of + false -> Tree; + {Name} when is_list(Name) -> + fail("bad metavariable: '~s'", [tl(Name)]); % drop v/n from name + Template -> Template + end. + +%% returns either a template or a lifted metavariable {String}, or 'false' +%% if Tree contained no metavariables +template_1(Tree) -> + case subtrees(Tree) of + [] -> + case metavar(Tree) of + {"v_"++Cs}=V when Cs =/= [] -> V; % to be lifted + {"n0"++Cs}=V when Cs =/= [] -> V; % to be lifted + {"v@"++Cs} when Cs =/= [] -> {'*',list_to_atom(Cs)}; + {"n9"++Cs} when Cs =/= [] -> {'*',list_to_integer(Cs)}; + {"v"++Cs} -> {list_to_atom(Cs)}; + {"n"++Cs} -> {list_to_integer(Cs)}; + false -> false + end; + Gs -> + case template_2(Gs, [], false) of + Gs1 when is_list(Gs1) -> + {template, type(Tree), erl_syntax:get_attrs(Tree), Gs1}; + Other -> + Other + end + end. + +template_2([G | Gs], As, Bool) -> + case template_3(G, [], false) of + {"v_"++Cs}=V when Cs =/= [] -> V; % lift further + {"n0"++Cs}=V when Cs =/= [] -> V; % lift further + {"v@"++Cs} when Cs =/= [] -> {'*',list_to_atom(Cs)}; % stop + {"n9"++Cs} when Cs =/= [] -> {'*',list_to_integer(Cs)}; % stop + {"v"++Cs} when is_list(Cs) -> {list_to_atom(Cs)}; % stop + {"n"++Cs} when is_list(Cs) -> {list_to_integer(Cs)}; % stop + false -> template_2(Gs, [G | As], Bool); + G1 -> template_2(Gs, [G1 | As], true) + end; +template_2([], _As, false) -> false; +template_2([], As, true) -> lists:reverse(As). + +template_3([T | Ts], As, Bool) -> + case template_1(T) of + {"v_"++Cs} when Cs =/= [] -> {"v"++Cs}; % lift + {"n0"++Cs} when Cs =/= [] -> {"n"++Cs}; % lift + false -> template_3(Ts, [T | As], Bool); + T1 -> template_3(Ts, [T1 | As], true) + end; +template_3([], _As, false) -> false; +template_3([], As, true) -> lists:reverse(As). + + +%% @doc Turn a template into a syntax tree representing the template. +%% Meta-variables in the template are turned into normal Erlang variables if +%% their names (after the metavariable prefix characters) begin with an +%% uppercase character. E.g., `_@Foo' in the template becomes the variable +%% `Foo' in the meta-template. Furthermore, variables ending with `@' are +%% automatically wrapped in a call to merl:term/1, so e.g. `_@Foo@ in the +%% template becomes `merl:term(Foo)' in the meta-template. + +-spec meta_template(template_or_templates()) -> tree_or_trees(). + +meta_template(Templates) when is_list(Templates) -> + [meta_template_1(T) || T <- Templates]; +meta_template(Template) -> + meta_template_1(Template). + +meta_template_1({template, Type, Attrs, Groups}) -> + erl_syntax:tuple( + [erl_syntax:atom(template), + erl_syntax:atom(Type), + erl_syntax:abstract(Attrs), + erl_syntax:list([erl_syntax:list([meta_template_1(T) || T <- G]) + || G <- Groups])]); +meta_template_1({Var}=V) -> + meta_template_2(Var, V); +meta_template_1({'*',Var}=V) -> + meta_template_2(Var, V); +meta_template_1(Leaf) -> + erl_syntax:abstract(Leaf). + +meta_template_2(Var, V) when is_atom(Var) -> + case atom_to_list(Var) of + [C|_]=Name when C >= $A, C =< $Z ; C >= $À, C =< $Þ, C /= $× -> + case lists:reverse(Name) of + "@"++([_|_]=RevRealName) -> % don't allow empty RealName + RealName = lists:reverse(RevRealName), + erl_syntax:application(erl_syntax:atom(merl), + erl_syntax:atom(term), + [erl_syntax:variable(RealName)]); + _ -> + %% plain automatic metavariable + erl_syntax:variable(Name) + end; + _ -> + erl_syntax:abstract(V) + end; +meta_template_2(Var, V) when is_integer(Var) -> + if Var > 9, (Var rem 10) =:= 9 -> + %% at least 2 digits, ends in 9: make it a Q-variable + if Var > 99, (Var rem 100) =:= 99 -> + %% at least 3 digits, ends in 99: wrap in merl:term/1 + Name = "Q" ++ integer_to_list(Var div 100), + erl_syntax:application(erl_syntax:atom(merl), + erl_syntax:atom(term), + [erl_syntax:variable(Name)]); + true -> + %% plain automatic Q-variable + Name = integer_to_list(Var div 10), + erl_syntax:variable("Q" ++ Name) + end; + true -> + erl_syntax:abstract(V) + end. + + + +-spec template_vars(template_or_templates()) -> [id()]. + +%% @doc Return an ordered list of the metavariables in the template. + +template_vars(Template) -> + template_vars(Template, []). + +template_vars(Templates, Vars) when is_list(Templates) -> + lists:foldl(fun template_vars_1/2, Vars, Templates); +template_vars(Template, Vars) -> + template_vars_1(Template, Vars). + +template_vars_1({template, _, _, Groups}, Vars) -> + lists:foldl(fun (G, V) -> lists:foldl(fun template_vars_1/2, V, G) end, + Vars, Groups); +template_vars_1({Var}, Vars) -> + ordsets:add_element(Var, Vars); +template_vars_1({'*',Var}, Vars) -> + ordsets:add_element(Var, Vars); +template_vars_1(_, Vars) -> + Vars. + + +-spec tree(template_or_templates()) -> tree_or_trees(). + +%% @doc Revert a template to a normal syntax tree. Any remaining +%% metavariables are turned into `@'-prefixed atoms or `909'-prefixed +%% integers. +%% @see template/1 + +tree(Templates) when is_list(Templates) -> + [tree_1(T) || T <- Templates]; +tree(Template) -> + tree_1(Template). + +tree_1({template, Type, Attrs, Groups}) -> + %% flattening here is needed for templates created via source transforms + Gs = [lists:flatten([tree_1(T) || T <- G]) || G <- Groups], + erl_syntax:set_attrs(make_tree(Type, Gs), Attrs); +tree_1({Var}) when is_atom(Var) -> + erl_syntax:atom(list_to_atom("@"++atom_to_list(Var))); +tree_1({Var}) when is_integer(Var) -> + erl_syntax:integer(list_to_integer("909"++integer_to_list(Var))); +tree_1({'*',Var}) when is_atom(Var) -> + erl_syntax:atom(list_to_atom("@@"++atom_to_list(Var))); +tree_1({'*',Var}) when is_integer(Var) -> + erl_syntax:integer(list_to_integer("9099"++integer_to_list(Var))); +tree_1(Leaf) -> + Leaf. % any syntax tree, not necessarily atomic (due to substitutions) + + +-spec subst(pattern_or_patterns(), env()) -> tree_or_trees(). + +%% @doc Substitute metavariables in a pattern or list of patterns, yielding +%% a syntax tree or list of trees as result. Both for normal metavariables +%% and glob metavariables, the substituted value may be a single element or +%% a list of elements. For example, if a list representing `1, 2, 3' is +%% substituted for `var' in either of `[foo, _@var, bar]' or `[foo, _@@var, +%% bar]', the result represents `[foo, 1, 2, 3, bar]'. + +subst(Trees, Env) when is_list(Trees) -> + [subst_0(T, Env) || T <- Trees]; +subst(Tree, Env) -> + subst_0(Tree, Env). + +subst_0(Tree, Env) -> + tree_1(subst_1(template(Tree), Env)). + + +-spec tsubst(pattern_or_patterns(), env()) -> template_or_templates(). + +%% @doc Like subst/2, but does not convert the result from a template back +%% to a tree. Useful if you want to do multiple separate substitutions. +%% @see subst/2 +%% @see tree/1 + +tsubst(Trees, Env) when is_list(Trees) -> + [subst_1(template(T), Env) || T <- Trees]; +tsubst(Tree, Env) -> + subst_1(template(Tree), Env). + +subst_1({template, Type, Attrs, Groups}, Env) -> + Gs1 = [lists:flatten([subst_1(T, Env) || T <- G]) || G <- Groups], + {template, Type, Attrs, Gs1}; +subst_1({Var}=V, Env) -> + case lists:keyfind(Var, 1, Env) of + {Var, TreeOrTrees} -> TreeOrTrees; + false -> V + end; +subst_1({'*',Var}=V, Env) -> + case lists:keyfind(Var, 1, Env) of + {Var, TreeOrTrees} -> TreeOrTrees; + false -> V + end; +subst_1(Leaf, _Env) -> + Leaf. + + +-spec alpha(pattern_or_patterns(), [{id(), id()}]) -> template_or_templates(). + +%% @doc Alpha converts a pattern (renames variables). Similar to tsubst/1, +%% but only renames variables (including globs). +%% @see tsubst/2 + +alpha(Trees, Env) when is_list(Trees) -> + [alpha_1(template(T), Env) || T <- Trees]; +alpha(Tree, Env) -> + alpha_1(template(Tree), Env). + +alpha_1({template, Type, Attrs, Groups}, Env) -> + Gs1 = [lists:flatten([alpha_1(T, Env) || T <- G]) || G <- Groups], + {template, Type, Attrs, Gs1}; +alpha_1({Var}=V, Env) -> + case lists:keyfind(Var, 1, Env) of + {Var, NewVar} -> {NewVar}; + false -> V + end; +alpha_1({'*',Var}=V, Env) -> + case lists:keyfind(Var, 1, Env) of + {Var, NewVar} -> {'*',NewVar}; + false -> V + end; +alpha_1(Leaf, _Env) -> + Leaf. + + +-spec match(pattern_or_patterns(), tree_or_trees()) -> + {ok, env()} | error. + +%% @doc Match a pattern against a syntax tree (or patterns against syntax +%% trees) returning an environment mapping variable names to subtrees; the +%% environment is always sorted on keys. Note that multiple occurrences of +%% metavariables in the pattern is not allowed, but is not checked. +%% +%% @see template/1 +%% @see switch/2 + +match(Patterns, Trees) when is_list(Patterns), is_list(Trees) -> + try {ok, match_1(Patterns, Trees, [])} + catch + error -> error + end; +match(Patterns, Tree) when is_list(Patterns) -> match(Patterns, [Tree]); +match(Pattern, Trees) when is_list(Trees) -> match([Pattern], Trees); +match(Pattern, Tree) -> + try {ok, match_template(template(Pattern), Tree, [])} + catch + error -> error + end. + +match_1([P|Ps], [T | Ts], Dict) -> + match_1(Ps, Ts, match_template(template(P), T, Dict)); +match_1([], [], Dict) -> + Dict; +match_1(_, _, _Dict) -> + erlang:error(merl_match_arity). + +%% match a template against a syntax tree +match_template({template, Type, _, Gs}, Tree, Dict) -> + case type(Tree) of + Type -> match_template_1(Gs, subtrees(Tree), Dict); + _ -> throw(error) % type mismatch + end; +match_template({Var}, _Tree, Dict) + when Var =:= '_' ; Var =:= 0 -> + Dict; % anonymous variable +match_template({Var}, Tree, Dict) -> + orddict:store(Var, Tree, Dict); +match_template(Tree1, Tree2, Dict) -> + %% if Tree1 is not a template, Tree1 and Tree2 are both syntax trees + case compare_trees(Tree1, Tree2) of + true -> Dict; + false -> throw(error) % different trees + end. + +match_template_1([G1 | Gs1], [G2 | Gs2], Dict) -> + match_template_2(G1, G2, match_template_1(Gs1, Gs2, Dict)); +match_template_1([], [], Dict) -> + Dict; +match_template_1(_, _, _Dict) -> + throw(error). % shape mismatch + +match_template_2([{Var} | Ts1], [_ | Ts2], Dict) + when Var =:= '_' ; Var =:= 0 -> + match_template_2(Ts1, Ts2, Dict); % anonymous variable +match_template_2([{Var} | Ts1], [Tree | Ts2], Dict) -> + match_template_2(Ts1, Ts2, orddict:store(Var, Tree, Dict)); +match_template_2([{'*',Var} | Ts1], Ts2, Dict) -> + match_glob(lists:reverse(Ts1), lists:reverse(Ts2), Var, Dict); +match_template_2([T1 | Ts1], [T2 | Ts2], Dict) -> + match_template_2(Ts1, Ts2, match_template(T1, T2, Dict)); +match_template_2([], [], Dict) -> + Dict; +match_template_2(_, _, _Dict) -> + throw(error). % shape mismatch + +%% match the tails in reverse order; no further globs allowed +match_glob([{'*',Var} | _], _, _, _) -> + fail("multiple glob variables in same match group: ~w", [Var]); +match_glob([T1 | Ts1], [T2 | Ts2], Var, Dict) -> + match_glob(Ts1, Ts2, Var, match_template(T1, T2, Dict)); +match_glob([], _Group, Var, Dict) when Var =:= '_' ; Var =:= 0 -> + Dict; % anonymous glob variable +match_glob([], Group, Var, Dict) -> + orddict:store(Var, lists:reverse(Group), Dict); +match_glob(_, _, _, _Dict) -> + throw(error). % shape mismatch + + +%% compare two syntax trees for equivalence +compare_trees(T1, T2) -> + Type1 = type(T1), + case type(T2) of + Type1 -> + case subtrees(T1) of + [] -> + case subtrees(T2) of + [] -> compare_leaves(Type1, T1, T2); + _Gs2 -> false % shape mismatch + end; + Gs1 -> + case subtrees(T2) of + [] -> false; % shape mismatch + Gs2 -> compare_trees_1(Gs1, Gs2) + end + end; + _Type2 -> + false % different tree types + end. + +compare_trees_1([G1 | Gs1], [G2 | Gs2]) -> + compare_trees_2(G1, G2) andalso compare_trees_1(Gs1, Gs2); +compare_trees_1([], []) -> + true; +compare_trees_1(_, _) -> + false. % shape mismatch + +compare_trees_2([T1 | Ts1], [T2 | Ts2]) -> + compare_trees(T1, T2) andalso compare_trees_2(Ts1, Ts2); +compare_trees_2([], []) -> + true; +compare_trees_2(_, _) -> + false. % shape mismatch + +compare_leaves(Type, T1, T2) -> + case Type of + atom -> + erl_syntax:atom_value(T1) + =:= erl_syntax:atom_value(T2); + char -> + erl_syntax:char_value(T1) + =:= erl_syntax:char_value(T2); + float -> + erl_syntax:float_value(T1) + =:= erl_syntax:float_value(T2); + integer -> + erl_syntax:integer_value(T1) + =:= erl_syntax:integer_value(T2); + string -> + erl_syntax:string_value(T1) + =:= erl_syntax:string_value(T2); + operator -> + erl_syntax:operator_name(T1) + =:= erl_syntax:operator_name(T2); + text -> + erl_syntax:text_string(T1) + =:= erl_syntax:text_string(T2); + variable -> + erl_syntax:variable_name(T1) + =:= erl_syntax:variable_name(T2); + _ -> + true % trivially equal nodes + end. + + +%% @doc Match against one or more clauses with patterns and optional guards. +%% +%% Note that clauses following a default action will be ignored. +%% +%% @see match/2 + +-type switch_clause() :: + {pattern_or_patterns(), guarded_actions()} + | {pattern_or_patterns(), guard_test(), switch_action()} + | default_action(). + +-type guarded_actions() :: guarded_action() | [guarded_action()]. + +-type guarded_action() :: switch_action() | {guard_test(), switch_action()}. + +-type switch_action() :: fun( (env()) -> any() ). + +-type guard_test() :: fun( (env()) -> boolean() ). + +-type default_action() :: fun( () -> any() ). + + +-spec switch(tree_or_trees(), [switch_clause()]) -> any(). + +switch(Trees, [{Patterns, GuardedActions} | Cs]) when is_list(GuardedActions) -> + switch_1(Trees, Patterns, GuardedActions, Cs); +switch(Trees, [{Patterns, GuardedAction} | Cs]) -> + switch_1(Trees, Patterns, [GuardedAction], Cs); +switch(Trees, [{Patterns, Guard, Action} | Cs]) -> + switch_1(Trees, Patterns, [{Guard, Action}], Cs); +switch(_Trees, [Default | _Cs]) when is_function(Default, 0) -> + Default(); +switch(_Trees, []) -> + erlang:error(merl_switch_clause); +switch(_Tree, _) -> + erlang:error(merl_switch_badarg). + +switch_1(Trees, Patterns, GuardedActions, Cs) -> + case match(Patterns, Trees) of + {ok, Env} -> + switch_2(Env, GuardedActions, Trees, Cs); + error -> + switch(Trees, Cs) + end. + +switch_2(Env, [{Guard, Action} | Bs], Trees, Cs) + when is_function(Guard, 1), is_function(Action, 1) -> + case Guard(Env) of + true -> Action(Env); + false -> switch_2(Env, Bs, Trees, Cs) + end; +switch_2(Env, [Action | _Bs], _Trees, _Cs) when is_function(Action, 1) -> + Action(Env); +switch_2(_Env, [], Trees, Cs) -> + switch(Trees, Cs); +switch_2(_Env, _, _Trees, _Cs) -> + erlang:error(merl_switch_badarg). + + +%% ------------------------------------------------------------------------ +%% Internal utility functions + +-dialyzer({nowarn_function, fail/1}). % no local return + +fail(Text) -> + fail(Text, []). + +fail(Fs, As) -> + throw({error, lists:flatten(io_lib:format(Fs, As))}). + +flatten_text([L | _]=Lines) when is_list(L) -> + lists:foldr(fun(S, T) -> S ++ [$\n | T] end, "", Lines); +flatten_text([B | _]=Lines) when is_binary(B) -> + lists:foldr(fun(S, T) -> binary_to_list(S) ++ [$\n | T] end, "", Lines); +flatten_text(Text) when is_binary(Text) -> + binary_to_list(Text); +flatten_text(Text) -> + Text. + +-spec metavar(tree()) -> {string()} | false. + +%% Check if a syntax tree represents a metavariable. If not, 'false' is +%% returned; otherwise, this returns a 1-tuple with a string containing the +%% variable name including lift/glob prefixes but without any leading +%% metavariable prefix, and instead prefixed with "v" for a variable or "i" +%% for an integer. +%% +%% Metavariables are atoms starting with @, variables starting with _@, +%% strings starting with "'@, or integers starting with 909. Following the +%% prefix, one or more _ or 0 characters (unless it's the last character in +%% the name) may be used to indicate "lifting" of the variable one or more +%% levels , and after that, a @ or 9 character indicates a glob metavariable +%% rather than a normal metavariable. If the name after the prefix is _ or +%% 0, the variable is treated as an anonymous catch-all pattern in matches. + +metavar(Tree) -> + case type(Tree) of + atom -> + case erl_syntax:atom_name(Tree) of + "@" ++ Cs when Cs =/= [] -> {"v"++Cs}; + _ -> false + end; + variable -> + case erl_syntax:variable_literal(Tree) of + "_@" ++ Cs when Cs =/= [] -> {"v"++Cs}; + _ -> false + end; + integer -> + case erl_syntax:integer_value(Tree) of + N when N >= 9090 -> + case integer_to_list(N) of + "909" ++ Cs -> {"n"++Cs}; + _ -> false + end; + _ -> false + end; + string -> + case erl_syntax:string_value(Tree) of + "'@" ++ Cs -> {"v"++Cs}; + _ -> false + end; + _ -> + false + end. + +%% wrappers around erl_syntax functions to provide more uniform shape of +%% generic subtrees (maybe this can be fixed in syntax_tools one day) + +type(T) -> + case erl_syntax:type(T) of + nil -> list; + Type -> Type + end. + +subtrees(T) -> + case erl_syntax:type(T) of + tuple -> + [erl_syntax:tuple_elements(T)]; %% don't treat {} as a leaf + nil -> + [[], []]; %% don't treat [] as a leaf, but as a list + list -> + case erl_syntax:list_suffix(T) of + none -> + [erl_syntax:list_prefix(T), []]; + S -> + [erl_syntax:list_prefix(T), [S]] + end; + binary_field -> + [[erl_syntax:binary_field_body(T)], + erl_syntax:binary_field_types(T)]; + clause -> + case erl_syntax:clause_guard(T) of + none -> + [erl_syntax:clause_patterns(T), [], + erl_syntax:clause_body(T)]; + G -> + [erl_syntax:clause_patterns(T), [G], + erl_syntax:clause_body(T)] + end; + receive_expr -> + case erl_syntax:receive_expr_timeout(T) of + none -> + [erl_syntax:receive_expr_clauses(T), [], []]; + E -> + [erl_syntax:receive_expr_clauses(T), [E], + erl_syntax:receive_expr_action(T)] + end; + record_expr -> + case erl_syntax:record_expr_argument(T) of + none -> + [[], [erl_syntax:record_expr_type(T)], + erl_syntax:record_expr_fields(T)]; + V -> + [[V], [erl_syntax:record_expr_type(T)], + erl_syntax:record_expr_fields(T)] + end; + record_field -> + case erl_syntax:record_field_value(T) of + none -> + [[erl_syntax:record_field_name(T)], []]; + V -> + [[erl_syntax:record_field_name(T)], [V]] + end; + _ -> + erl_syntax:subtrees(T) + end. + +make_tree(list, [P, []]) -> erl_syntax:list(P); +make_tree(list, [P, [S]]) -> erl_syntax:list(P, S); +make_tree(tuple, [E]) -> erl_syntax:tuple(E); +make_tree(binary_field, [[B], Ts]) -> erl_syntax:binary_field(B, Ts); +make_tree(clause, [P, [], B]) -> erl_syntax:clause(P, none, B); +make_tree(clause, [P, [G], B]) -> erl_syntax:clause(P, G, B); +make_tree(receive_expr, [C, [], _A]) -> erl_syntax:receive_expr(C); +make_tree(receive_expr, [C, [E], A]) -> erl_syntax:receive_expr(C, E, A); +make_tree(record_expr, [[], [T], F]) -> erl_syntax:record_expr(T, F); +make_tree(record_expr, [[E], [T], F]) -> erl_syntax:record_expr(E, T, F); +make_tree(record_field, [[N], []]) -> erl_syntax:record_field(N); +make_tree(record_field, [[N], [E]]) -> erl_syntax:record_field(N, E); +make_tree(Type, Groups) -> + erl_syntax:make_tree(Type, Groups). + +merge_comments(_StartLine, [], [T]) -> T; +merge_comments(_StartLine, [], Ts) -> Ts; +merge_comments(StartLine, Comments, Ts) -> + merge_comments(StartLine, Comments, Ts, []). + +merge_comments(_StartLine, [], [], [T]) -> T; +merge_comments(_StartLine, [], [T], []) -> T; +merge_comments(_StartLine, [], Ts, Acc) -> + lists:reverse(Acc, Ts); +merge_comments(StartLine, Cs, [], Acc) -> + merge_comments(StartLine, [], [], + [erl_syntax:set_pos( + erl_syntax:comment(Indent, Text), + anno(StartLine + Line - 1)) + || {Line, _, Indent, Text} <- Cs] ++ Acc); +merge_comments(StartLine, [C|Cs], [T|Ts], Acc) -> + {Line, _Col, Indent, Text} = C, + CommentLine = StartLine + Line - 1, + case erl_syntax:get_pos(T) of + Pos when Pos < CommentLine -> + %% TODO: traverse sub-tree rather than only the top level nodes + merge_comments(StartLine, [C|Cs], Ts, [T|Acc]); + CommentLine -> + Tc = erl_syntax:add_postcomments( + [erl_syntax:comment(Indent, Text)], T), + merge_comments(StartLine, Cs, [Tc|Ts], Acc); + _ -> + Tc = erl_syntax:add_precomments( + [erl_syntax:comment(Indent, Text)], T), + merge_comments(StartLine, Cs, [Tc|Ts], Acc) + end. + +a0() -> + anno(0). + +anno(Location) -> + erl_anno:new(Location). |