1 files changed, 49 insertions, 7 deletions

diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 3d17557e01..082809b8a0 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -77,7 +77,8 @@
 		splitwith/2,keyfind/3,sort/1,foreach/2,droplast/1,last/1]).
 -import(ordsets, [add_element/2,del_element/2,is_element/2,
 		  union/1,union/2,intersection/2,subtract/2]).
--import(cerl, [ann_c_cons/3,ann_c_cons_skel/3,ann_c_tuple/2,c_tuple/1]).
+-import(cerl, [ann_c_cons/3,ann_c_cons_skel/3,ann_c_tuple/2,c_tuple/1,
+	       ann_c_map/2, ann_c_map/3]).
 
 -include("core_parse.hrl").
 
@@ -515,12 +516,20 @@ expr({map,L,Es0}, St0) ->
     % in map construction.
     {Es1,Eps,St1} = map_pair_list(Es0, St0),
     A = lineno_anno(L, St1),
-    {#c_map{anno=A,es=Es1},Eps,St1};
+    {ann_c_map(A,Es1),Eps,St1};
 expr({map,L,M0,Es0}, St0) ->
-    {M1,Mps,St1} = safe(M0, St0),
-    {Es1,Eps,St2} = map_pair_list(Es0, St1),
-    A = lineno_anno(L, St2),
-    {#c_map{anno=A,var=M1,es=Es1},Mps++Eps,St2};
+    try expr_map(M0,Es0,lineno_anno(L, St0),St0) of
+	{_,_,_}=Res -> Res
+    catch
+	throw:bad_map ->
+	    St = add_warning(L, bad_map, St0),
+	    LineAnno = lineno_anno(L, St),
+	    As = [#c_literal{anno=LineAnno,val=badarg}],
+	    {#icall{anno=#a{anno=LineAnno},	%Must have an #a{}
+		    module=#c_literal{anno=LineAnno,val=erlang},
+		    name=#c_literal{anno=LineAnno,val=error},
+		    args=As},[],St}
+    end;
 expr({bin,L,Es0}, St0) ->
     try expr_bin(Es0, lineno_anno(L, St0), St0) of
 	{_,_,_}=Res -> Res
@@ -730,6 +739,37 @@ make_bool_switch_guard(L, E, V, T, F) ->
       {clause,NegL,[V],[],[V]}
      ]}.
 
+expr_map(M0,Es0,A,St0) ->
+    {M1,Mps,St1} = safe(M0, St0),
+    case is_valid_map_src(M1) of
+	true ->
+	    case {M1,Es0} of
+		{#c_var{}, []} ->
+		    %% transform M#{} to is_map(M)
+		    {Vpat,St2} = new_var(St1),
+		    {Fpat,St3} = new_var(St2),
+		    Cs = [#iclause{
+			   anno=A,
+			   pats=[Vpat],
+			   guard=[#icall{anno=#a{anno=A},
+				   module=#c_literal{anno=A,val=erlang},
+			           name=#c_literal{anno=A,val=is_map},
+				   args=[Vpat]}],
+			   body=[Vpat]}],
+		    Fc = fail_clause([Fpat], A, #c_literal{val=badarg}),
+		    {#icase{anno=#a{anno=A},args=[M1],clauses=Cs,fc=Fc},Mps,St3};
+		{_,_} ->
+		    {Es1,Eps,St2} = map_pair_list(Es0, St1),
+		    {ann_c_map(A,M1,Es1),Mps++Eps,St2}
+	    end;
+	false -> throw(bad_map)
+    end.
+
+is_valid_map_src(#c_literal{val = M}) when is_map(M) -> true;
+is_valid_map_src(#c_map{})  -> true;
+is_valid_map_src(#c_var{})  -> true;
+is_valid_map_src(_)         -> false.
+
 map_pair_list(Es, St) ->
     foldr(fun
 	    ({map_field_assoc,L,K0,V0}, {Ces,Esp,St0}) ->
@@ -2256,7 +2296,9 @@ is_simple_list(Es) -> lists:all(fun is_simple/1, Es).
 format_error(nomatch) ->
     "pattern cannot possibly match";
 format_error(bad_binary) ->
-    "binary construction will fail because of a type mismatch".
+    "binary construction will fail because of a type mismatch";
+format_error(bad_map) ->
+    "map construction will fail because of a type mismatch".
 
 add_warning(Line, Term, #core{ws=Ws,file=[{file,File}]}=St) when Line >= 0 ->
     St#core{ws=[{File,[{location(Line),?MODULE,Term}]}|Ws]};