File 2181-erl_lint-Warn-on-updating-map-record-liter... of Package erlang

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File 2181-erl_lint-Warn-on-updating-map-record-literals.patch of Package erlang (Revision a95c38533dd94a5c195230b3b146d029)

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From 239f7c1ea0645fc62c83035e3f3455a58a1d8afc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20H=C3=B6gberg?= <john@erlang.org>
Date: Tue, 30 Jan 2024 10:09:47 +0100
Subject: [PATCH] erl_lint: Warn on updating map/record literals

---
 lib/stdlib/src/erl_lint.erl        | 43 +++++++++++++++++++++++++++---
 lib/stdlib/test/erl_lint_SUITE.erl | 40 ++++++++++++++++++++++-----
 2 files changed, 74 insertions(+), 9 deletions(-)

diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index 4c57859c74..1a779d49c2 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -316,6 +316,8 @@ format_error({obsolete_guard_overridden,Test}) ->
 format_error({too_many_arguments,Arity}) ->
     io_lib:format("too many arguments (~w) - "
 		  "maximum allowed is ~w", [Arity,?MAX_ARGUMENTS]);
+format_error(update_literal) ->
+    "expression updates a literal";
 %% --- patterns and guards ---
 format_error(illegal_pattern) -> "illegal pattern";
 format_error(illegal_map_key) -> "illegal map key in pattern";
@@ -682,6 +684,9 @@ start(File, Opts) ->
                       true, Opts)},
          {match_float_zero,
           bool_option(warn_match_float_zero, nowarn_match_float_zero,
+                      true, Opts)},
+         {update_literal,
+          bool_option(warn_update_literal, nowarn_update_literal,
                       true, Opts)}
 	],
     Enabled1 = [Category || {Category,true} <- Enabled0],
@@ -2429,10 +2434,10 @@ expr({tuple,_Anno,Es}, Vt, St) ->
     expr_list(Es, Vt, St);
 expr({map,_Anno,Es}, Vt, St) ->
     map_fields(Es, Vt, check_assoc_fields(Es, St), fun expr_list/3);
-expr({map,_Anno,Src,Es}, Vt, St) ->
+expr({map,Anno,Src,Es}, Vt, St) ->
     {Svt,St1} = expr(Src, Vt, St),
     {Fvt,St2} = map_fields(Es, Vt, St1, fun expr_list/3),
-    {vtupdate(Svt, Fvt),St2};
+    {vtupdate(Svt, Fvt), warn_if_literal_update(Anno, Src, St2)};
 expr({record_index,Anno,Name,Field}, _Vt, St) ->
     check_record(Anno, Name, St,
                  fun (Dfs, St1) -> record_field(Field, Name, Dfs, St1) end);
@@ -2455,7 +2460,7 @@ expr({record,Anno,Rec,Name,Upds}, Vt, St0) ->
                                   update_fields(Upds, Name, Dfs, Vt, St)
                           end ),
     case has_wildcard_field(Upds) of
-        no -> {vtmerge(Rvt, Usvt),St2};
+        no -> {vtmerge(Rvt, Usvt), warn_if_literal_update(Anno, Rec, St2)};
         WildAnno -> {[],add_error(WildAnno, {wildcard_in_update,Name}, St2)}
     end;
 expr({bin,_Anno,Fs}, Vt, St) ->
@@ -4151,6 +4156,38 @@ has_wildcard_field([{record_field,_Af,{var,Aa,'_'},_Val}|_Fs]) -> Aa;
 has_wildcard_field([_|Fs]) -> has_wildcard_field(Fs);
 has_wildcard_field([]) -> no.
 
+%% Raises a warning when updating a (map, record) literal, as that is most
+%% likely unintentional. For example, if we forget a comma in a list like the
+%% following:
+%%
+%%    -record(foo, {bar}).
+%%
+%%    list() ->
+%%        [
+%%            #foo{bar = foo} %% MISSING COMMA!
+%%            #foo{bar = bar}
+%%        ].
+%%
+%% We only raise a warning when the expression-to-be-updated is a map or a
+%% record, as better warnings will be raised elsewhere for other funny
+%% constructs.
+warn_if_literal_update(Anno, Expr, St) ->
+    case is_literal_update(Expr) andalso is_warn_enabled(update_literal, St) of
+        true -> add_warning(Anno, update_literal, St);
+        false -> St
+    end.
+
+is_literal_update({record, _, Inner, _, _}) ->
+    is_literal_update(Inner);
+is_literal_update({record, _, _, _}) ->
+    true;
+is_literal_update({map, _, Inner, _}) ->
+    is_literal_update(Inner);
+is_literal_update({map, _, _}) ->
+    true;
+is_literal_update(_Expr) ->
+    false.
+
 %% check_remote_function(Anno, ModuleName, FuncName, [Arg], State) -> State.
 %%  Perform checks on known remote calls.
 
diff --git a/lib/stdlib/test/erl_lint_SUITE.erl b/lib/stdlib/test/erl_lint_SUITE.erl
index c54c1bd00d..184d2fcf55 100644
--- a/lib/stdlib/test/erl_lint_SUITE.erl
+++ b/lib/stdlib/test/erl_lint_SUITE.erl
@@ -85,7 +85,8 @@
          redefined_builtin_type/1,
          tilde_k/1,
          match_float_zero/1,
-         undefined_module/1]).
+         undefined_module/1,
+         update_literal/1]).
 
 suite() ->
     [{ct_hooks,[ts_install_cth]},
@@ -119,7 +120,8 @@ all() ->
      tilde_k,
      singleton_type_var_errors,
      match_float_zero,
-     undefined_module].
+     undefined_module,
+     update_literal].
 
 groups() -> 
     [{unused_vars_warn, [],
@@ -4049,10 +4051,11 @@ maps(Config) ->
                   ok.
             ">>,
            [],
-           {errors,[{{2,24},erl_lint,illegal_map_construction},
-                    {{4,24},erl_lint,illegal_map_construction},
-                    {{8,36},erl_lint,illegal_map_construction}],
-            []}},
+           {error,
+            [{{2,24},erl_lint,illegal_map_construction},
+             {{4,24},erl_lint,illegal_map_construction},
+             {{8,36},erl_lint,illegal_map_construction}],
+            [{{5,20},erl_lint,update_literal}]}},
           {illegal_pattern,
            <<"t(#{ a := A,
                    c => d,
@@ -5330,6 +5333,31 @@ undefined_module(Config) ->
 
     ok.
 
+update_literal(Config) ->
+    Ts = [{update_record_literal,
+           <<"-record(a, {b}).
+             t() -> #a{}#a{}#a{b=aoeu}.
+             k() -> A = #a{}, A#a{}#a{b=aoeu}.">>,
+           [],
+           {warnings,[{{2,25},erl_lint,update_literal},
+                      {{2,29},erl_lint,update_literal}]}},
+          {update_map_literal_assoc,
+           <<"t() -> #{}#{}#{b=>aoeu}.
+              k() -> A = #{}, A#{}#{b=>aoeu}.">>,
+           [],
+           {warnings,[{{1,31},erl_lint,update_literal},
+                      {{1,34},erl_lint,update_literal}]}},
+          {update_map_literal_exact,
+           <<"t() -> #{}#{}#{b:=aoeu}.
+              k() -> A = #{}, A#{}#{b:=aoeu}.">>,
+           [],
+           {warnings,[{{1,31},erl_lint,update_literal},
+                      {{1,34},erl_lint,update_literal}]}}
+         ],
+    [] = run(Config, Ts),
+
+    ok.
+
 %%%
 %%% Common utilities.
 %%%
-- 
2.35.3

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File 2181-erl_lint-Warn-on-updating-map-record-literals.patch of Package erlang (Revision a95c38533dd94a5c195230b3b146d029)

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