compiler: Throw 'nomatch' on matching with bad binary keys

Even if a binary key is written as a literal the compiler may
choose to make an expression. Emit a warning in those cases
and saying the case will not match.

This is a limitation in current implementation.

2 files changed, 18 insertions, 2 deletions

diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 04210ae243..46db9139c4 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -1595,7 +1595,9 @@ pattern_map_pair({map_field_exact,L,K,V}, St) ->
 	{bin,L,Es0} ->
 	    case constant_bin(Es0) of
 		error ->
-		    throw(badmatch);
+		    %% this will throw a cryptic error message
+		    %% but it is better than nothing
+		    throw(nomatch);
 		Bin ->
 		    #c_literal{anno=lineno_anno(L,St),val=Bin}
 	    end;
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index e8ec48df14..ad4ad91f74 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -600,7 +600,21 @@ maps(Config) when is_list(Config) ->
 		 ok.
            ">>,
            [],
-	   {warnings,[{3,v3_core,bad_map}]}}],
+	   {warnings,[{3,v3_core,bad_map}]}},
+	   {bad_map_literal_key,
+           <<"
+             t() ->
+		 V = id(1),
+		 M = id(#{ <<$h,$i>> => V }),
+		 V = case M of
+		    #{ <<0:257>> := Val } -> Val;
+		    #{ <<$h,$i>> := Val } -> Val
+		 end,
+		 ok.
+	     id(I) -> I.
+           ">>,
+           [],
+	   {warnings,[{6,v3_core,nomatch}]}}],
     run(Config, Ts),
     ok.