From be782d05bcd259b229efcac47c0566e4026cf1f6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn-Egil=20Dahlberg?= <egil@erlang.org>
Date: Tue, 24 Sep 2013 15:22:41 +0200
Subject: compiler: Check for duplicate key literals in Map
If a literal key already is present in a Map update the latter should be used.
Warn for previous duplicates in the Map.
---
lib/compiler/src/sys_core_fold.erl | 30 ++++++++++++++++++++++++++++--
1 file changed, 28 insertions(+), 2 deletions(-)
(limited to 'lib')
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 672a8b94c0..cdbe2d0753 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -418,8 +418,31 @@ expr(#c_try{anno=A,arg=E0,vars=Vs0,body=B0,evars=Evs0,handler=H0}=Try, _, Sub0)
expr_list(Es, Ctxt, Sub) ->
[expr(E, Ctxt, Sub) || E <- Es].
+%% traverse pairs in reverse
+%% - remove later literals since they will be overwritten.
+
pair_list(Es, Ctxt, Sub) ->
- [pair(E, Ctxt, Sub) || E <- Es].
+ pair_list_reversed(lists:reverse(Es), Ctxt, Sub, [], gb_sets:empty()).
+
+pair_list_reversed([],_,_,Es,_) -> Es;
+pair_list_reversed([E|Es],Ctxt,Sub,Out,Keys) ->
+ Pair = pair(E,Ctxt,Sub),
+ case map_has_key(Pair,Keys) of
+ {false,Keys1} ->
+ pair_list_reversed(Es,Ctxt,Sub,[Pair|Out],Keys1);
+ {true,K} ->
+ add_warning(E, {map_pair_key_overloaded,K}),
+ pair_list_reversed(Es,Ctxt,Sub,Out,Keys)
+ end.
+
+%% check if key already is present in map, i.e. #{ a=>1, a=>2 }
+%% where 'a' is duplicate. Update maps set with the key if not present.
+
+map_has_key(#c_map_pair{key=#c_literal{val=K}},Ks) ->
+ case gb_sets:is_element(K,Ks) of
+ false -> {false, gb_sets:add(K,Ks)};
+ true -> {true, K}
+ end.
pair(#c_map_pair{key=K,val=V}, effect, Sub) ->
make_effect_seq([K,V], Sub);
@@ -697,7 +720,7 @@ useless_call(effect, #c_call{anno=Anno,
useless_call(_, _) -> no.
%% make_effect_seq([Expr], Sub) -> #c_seq{}|void()
-%% Convert a list of epressions evaluated in effect context to a chain of
+%% Convert a list of expressions evaluated in effect context to a chain of
%% #c_seq{}. The body in the innermost #c_seq{} will be void().
%% Anything that will not have any effect will be thrown away.
@@ -3019,6 +3042,9 @@ format_error(result_ignored) ->
"(suppress the warning by assigning the expression to the _ variable)";
format_error(useless_building) ->
"a term is constructed, but never used";
+format_error({map_pair_key_overloaded,K}) ->
+ M = io_lib:format("the key ~p is used multiple times in map value association",[K]),
+ flatten(M);
format_error(bin_opt_alias) ->
"INFO: the '=' operator will prevent delayed sub binary optimization";
format_error(bin_partition) ->
--
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