Merge branch 'bjorn/compiler/map-fixes'

* bjorn/compiler/map-fixes:
  cerl: Remove a clause in fold_map_pairs/3 that will never be reached
  Move grouping of map constructions from v3_core to v3_kernel
  core_pp: Correct printing of map literals
  Strengthen and modernize compile_SUITE
  core_parse: Always fold literal conses
  cerl: Make sure that we preserve the invariants for maps
  cerl_clauses: Fix indentation
  sys_core_fold: Strengthen optimization of letrecs in effect context
  Fix handling of binary map keys in comprehensions
  core_lib: Teach is_var_used/2 to handle keys in map patterns
  warnings_SUITE: Eliminate compiler warning for a shadowed variable
  lc_SUITE: Add shadow/1
  Modernize lc_SUITE

9 files changed, 217 insertions, 180 deletions

diff --git a/lib/compiler/src/cerl.erl b/lib/compiler/src/cerl.erl
index 7a2c3d70de..1a2957ee31 100644
--- a/lib/compiler/src/cerl.erl
+++ b/lib/compiler/src/cerl.erl
@@ -123,11 +123,13 @@
 	 bitstr_flags/1,
 
 	 %% keep map exports here for now
+	 c_map_pattern/1,
 	 map_es/1,
 	 map_arg/1,
 	 update_c_map/3,
 	 c_map/1, is_c_map_empty/1,
 	 ann_c_map/2, ann_c_map/3,
+	 ann_c_map_pattern/2,
 	 map_pair_op/1,map_pair_key/1,map_pair_val/1,
 	 update_c_map_pair/4,
 	 c_map_pair/2,
@@ -1590,7 +1592,17 @@ map_arg(#c_map{arg=M}) ->
 -spec c_map([c_map_pair()]) -> c_map().
 
 c_map(Pairs) ->
-    #c_map{es=Pairs}.
+    ann_c_map([], Pairs).
+
+-spec c_map_pattern([c_map_pair()]) -> c_map().
+
+c_map_pattern(Pairs) ->
+    #c_map{es=Pairs, is_pat=true}.
+
+-spec ann_c_map_pattern([term()], [c_map_pair()]) -> c_map().
+
+ann_c_map_pattern(As, Pairs) ->
+    #c_map{anno=As, es=Pairs, is_pat=true}.
 
 -spec is_c_map_empty(c_map() | c_literal()) -> boolean().
 
@@ -1598,25 +1610,13 @@ is_c_map_empty(#c_map{ es=[] }) -> true;
 is_c_map_empty(#c_literal{val=M}) when is_map(M),map_size(M) =:= 0 -> true;
 is_c_map_empty(_) -> false.
 
--spec ann_c_map([term()], [cerl()]) -> c_map() | c_literal().
+-spec ann_c_map([term()], [c_map_pair()]) -> c_map() | c_literal().
 
-ann_c_map(As,Es) ->
+ann_c_map(As, Es) ->
     ann_c_map(As, #c_literal{val=#{}}, Es).
 
 -spec ann_c_map([term()], c_map() | c_literal(), [c_map_pair()]) -> c_map() | c_literal().
 
-ann_c_map(As,#c_literal{val=Mval}=M,Es) when is_map(Mval), map_size(Mval) =:= 0 ->
-    Pairs = [[Ck,Cv]||#c_map_pair{key=Ck,val=Cv}<-Es],
-    IsLit = lists:foldl(fun(Pair,Res) ->
-		Res andalso is_lit_list(Pair)
-	end, true, Pairs),
-    Fun = fun(Pair) -> [K,V] = lit_list_vals(Pair), {K,V} end,
-    case IsLit of
-	false ->
-	    #c_map{arg=M, es=Es, anno=As };
-	true ->
-	    #c_literal{anno=As, val=maps:from_list(lists:map(Fun, Pairs))}
-	end;
 ann_c_map(As,#c_literal{val=M},Es) when is_map(M) ->
     fold_map_pairs(As,Es,M);
 ann_c_map(As,M,Es) ->
@@ -1644,14 +1644,14 @@ fold_map_pairs(As,[#c_map_pair{op=#c_literal{val=exact},key=Ck,val=Cv}=E|Es],M)
 	    end;
 	false ->
 	    #c_map{arg=#c_literal{val=M,anno=As}, es=[E|Es], anno=As }
-    end;
-fold_map_pairs(As,Es,M) ->
-    #c_map{arg=#c_literal{val=M,anno=As}, es=Es, anno=As }.
+    end.
 
-%-spec update_c_map(c_map() | c_literal(), [c_map_pair()]) -> c_map() | c_literal().
+-spec update_c_map(c_map(), cerl(), [cerl()]) -> c_map() | c_literal().
 
-update_c_map(Old,M,Es) ->
-    #c_map{arg=M, es = Es, anno = get_ann(Old)}.
+update_c_map(#c_map{is_pat=true}=Old, M, Es) ->
+    Old#c_map{arg=M, es=Es};
+update_c_map(#c_map{is_pat=false}=Old, M, Es) ->
+    ann_c_map(get_ann(Old), M, Es).
 
 map_pair_key(#c_map_pair{key=K}) -> K.
 map_pair_val(#c_map_pair{val=V}) -> V.
diff --git a/lib/compiler/src/cerl_clauses.erl b/lib/compiler/src/cerl_clauses.erl
index 87bd47c08b..ef74c5b76f 100644
--- a/lib/compiler/src/cerl_clauses.erl
+++ b/lib/compiler/src/cerl_clauses.erl
@@ -354,29 +354,29 @@ match(P, E, Bs) ->
 			    {false, Bs}
 		    end
 	    end;
-    map ->
-        %% The most we can do is to say "definitely no match" if a
-        %% map pattern is matched against non-map data.
-        case E of
-            any ->
-                {false, Bs};
-            _ ->
-                case type(E) of
-		    literal ->
-			case is_map(concrete(E)) of
-			    false ->
-				none;
-			    true ->
-				{false, Bs}
-			end;
-                    cons ->
-                        none;
-                    tuple ->
-                        none;
-                    _ ->
-                        {false, Bs}
-                end
-        end;
+	map ->
+	    %% The most we can do is to say "definitely no match" if a
+	    %% map pattern is matched against non-map data.
+	    case E of
+		any ->
+		    {false, Bs};
+		_ ->
+		    case type(E) of
+			literal ->
+			    case is_map(concrete(E)) of
+				false ->
+				    none;
+				true ->
+				    {false, Bs}
+			    end;
+			cons ->
+			    none;
+			tuple ->
+			    none;
+			_ ->
+			    {false, Bs}
+		    end
+	    end;
 	_ ->
 	    match_1(P, E, Bs)
     end.
diff --git a/lib/compiler/src/core_lib.erl b/lib/compiler/src/core_lib.erl
index 0d95971f91..730e3a5317 100644
--- a/lib/compiler/src/core_lib.erl
+++ b/lib/compiler/src/core_lib.erl
@@ -236,10 +236,15 @@ vu_pat_seg_list(V, Ss, St) ->
 			end
 		end, St, Ss).
 
-vu_map_pairs(V, [#c_map_pair{val=Pat}|T], St0) ->
-    case vu_pattern(V, Pat, St0) of
-	{true,_}=St -> St;
-	St -> vu_map_pairs(V, T, St)
+vu_map_pairs(V, [#c_map_pair{key=Key,val=Pat}|T], St0) ->
+    case vu_expr(V, Key) of
+	true ->
+	    {true,false};
+	false ->
+	    case vu_pattern(V, Pat, St0) of
+		{true,_}=St -> St;
+		St -> vu_map_pairs(V, T, St)
+	    end
     end;
 vu_map_pairs(_, [], St) -> St.
 
diff --git a/lib/compiler/src/core_parse.hrl b/lib/compiler/src/core_parse.hrl
index 4a00535360..7fd4a82e4e 100644
--- a/lib/compiler/src/core_parse.hrl
+++ b/lib/compiler/src/core_parse.hrl
@@ -72,7 +72,8 @@
 
 -record(c_map, {anno=[],
 		arg=#c_literal{val=#{}} :: cerl:c_var() | cerl:c_literal(),
-		es :: [cerl:c_map_pair()]}).
+		es :: [cerl:c_map_pair()],
+		is_pat=false :: boolean()}).
 
 -record(c_map_pair, {anno=[],
 	             op :: #c_literal{val::'assoc'} | #c_literal{val::'exact'},
diff --git a/lib/compiler/src/core_parse.yrl b/lib/compiler/src/core_parse.yrl
index a66ad4235f..849f801a11 100644
--- a/lib/compiler/src/core_parse.yrl
+++ b/lib/compiler/src/core_parse.yrl
@@ -182,23 +182,23 @@ atomic_pattern -> atomic_literal : '$1'.
 tuple_pattern -> '{' '}' : c_tuple([]).
 tuple_pattern -> '{' anno_patterns '}' : c_tuple('$2').
 
-map_pattern -> '~' '{' '}' '~' : #c_map{es=[]}.
+map_pattern -> '~' '{' '}' '~' : c_map_pattern([]).
 map_pattern -> '~' '{' map_pair_patterns '}' '~' :
-		   #c_map{es=lists:sort('$3')}.
+		   c_map_pattern(lists:sort('$3')).
 
 map_pair_patterns -> map_pair_pattern : ['$1'].
 map_pair_patterns -> map_pair_pattern ',' map_pair_patterns : ['$1' | '$3'].
 
-map_pair_pattern -> '~' '<' anno_pattern ',' anno_pattern '>' :
+map_pair_pattern -> '~' '<' anno_expression ',' anno_pattern '>' :
 			#c_map_pair{op=#c_literal{val=exact},key='$3',val='$5'}.
 
 cons_pattern -> '[' anno_pattern tail_pattern :
-		    #c_cons{hd='$2',tl='$3'}.
+		    c_cons('$2', '$3').
 
 tail_pattern -> ']' : #c_literal{val=[]}.
 tail_pattern -> '|' anno_pattern ']' : '$2'.
 tail_pattern -> ',' anno_pattern tail_pattern :
-		    #c_cons{hd='$2',tl='$3'}.
+		    c_cons('$2', '$3').
 
 binary_pattern -> '#' '{' '}' '#' : #c_binary{segments=[]}.
 binary_pattern -> '#' '{' segment_patterns '}' '#' : #c_binary{segments='$3'}.
@@ -206,7 +206,7 @@ binary_pattern -> '#' '{' segment_patterns '}' '#' : #c_binary{segments='$3'}.
 segment_patterns -> segment_pattern ',' segment_patterns : ['$1' | '$3'].
 segment_patterns -> segment_pattern : ['$1'].
 
-segment_pattern -> '#' '<' anno_pattern '>' '(' anno_patterns ')':
+segment_pattern -> '#' '<' anno_pattern '>' '(' anno_expressions ')':
 	case '$6' of
 	    [S,U,T,Fs] ->
 		#c_bitstr{val='$3',size=S,unit=U,type=T,flags=Fs};
@@ -279,15 +279,15 @@ cons_literal -> '[' literal tail_literal : c_cons('$2', '$3').
 
 tail_literal -> ']' : #c_literal{val=[]}.
 tail_literal -> '|' literal ']' : '$2'.
-tail_literal -> ',' literal tail_literal : #c_cons{hd='$2',tl='$3'}.
+tail_literal -> ',' literal tail_literal : c_cons('$2', '$3').
 
 tuple -> '{' '}' : c_tuple([]).
 tuple -> '{' anno_expressions '}' : c_tuple('$2').
 
-map_expr -> '~' '{' '}' '~' : #c_map{es=[]}.
-map_expr -> '~' '{' map_pairs '}' '~' : #c_map{es='$3'}.
-map_expr -> '~' '{' map_pairs '|' variable '}' '~' : #c_map{arg='$5',es='$3'}.
-map_expr -> '~' '{' map_pairs '|' map_expr '}' '~' : #c_map{arg='$5',es='$3'}.
+map_expr -> '~' '{' '}' '~' : c_map([]).
+map_expr -> '~' '{' map_pairs '}' '~' : c_map('$3').
+map_expr -> '~' '{' map_pairs '|' variable '}' '~' : ann_c_map([], '$5', '$3').
+map_expr -> '~' '{' map_pairs '|' map_expr '}' '~' : ann_c_map([], '$5', '$3').
 
 map_pairs -> map_pair : ['$1'].
 map_pairs -> map_pair ',' map_pairs : ['$1' | '$3'].
@@ -307,7 +307,7 @@ tail -> '|' anno_expression ']' : '$2'.
 tail -> ',' anno_expression tail : c_cons('$2', '$3').
 
 binary -> '#' '{' '}' '#' : #c_literal{val = <<>>}.
-binary -> '#' '{' segments '}' '#' : #c_binary{segments='$3'}.
+binary -> '#' '{' segments '}' '#' : make_binary('$3').
 
 segments -> segment ',' segments : ['$1' | '$3'].
 segments -> segment : ['$1'].
@@ -410,9 +410,55 @@ Erlang code.
 
 -include("core_parse.hrl").
 
--import(cerl, [c_cons/2,c_tuple/1]).
+-import(cerl, [ann_c_map/3,c_cons/2,c_map/1,c_map_pattern/1,c_tuple/1]).
 
 tok_val(T) -> element(3, T).
 tok_line(T) -> element(2, T).
 
+%% make_binary([#c_bitstr{}]) -> #c_binary{} | #c_literal{}
+%%  Create either #c_binary{} or #c_literal{} from the binary segments.
+%%  In certain contexts, such as keys for maps, only literals and
+%%  variables are allowed, so we must not create a #c_binary{}
+%%  record in those situation.
+%%
+%%  To keep this function simple, we use a crude heuristic. We will
+%%  assume that Core Erlang has been produced by core_pp. If the
+%%  segments *could* have been output from a literal binary by
+%%  core_pp, we will create a #c_literal{}. Otherwise we will create a
+%%  #c_binary{} record.
+
+make_binary(Segs) ->
+    try make_lit_bin(<<>>, Segs) of
+	Bs when is_bitstring(Bs) ->
+	    #c_literal{val=Bs}
+    catch
+	throw:impossible ->
+	    #c_binary{segments=Segs}
+    end.
+
+make_lit_bin(Acc, [#c_bitstr{val=I0,size=Sz0,unit=U0,type=Type0,flags=F0}|T]) ->
+    I = get_lit_val(I0),
+    Sz = get_lit_val(Sz0),
+    U = get_lit_val(U0),
+    Type = get_lit_val(Type0),
+    F = get_lit_val(F0),
+    if
+	is_integer(I), U =:= 1, Type =:= integer, F =:= [unsigned,big] ->
+	    ok;
+	true ->
+	    throw(impossible)
+    end,
+    if
+	Sz =< 8, T =:= [] ->
+	    <<Acc/binary,I:Sz>>;
+	Sz =:= 8 ->
+	    make_lit_bin(<<Acc/binary,I:8>>, T);
+	true ->
+	    throw(impossible)
+    end;
+make_lit_bin(Acc, []) -> Acc.
+
+get_lit_val(#c_literal{val=Val}) -> Val;
+get_lit_val(_) -> throw(impossible).
+
 %% vim: syntax=erlang
diff --git a/lib/compiler/src/core_pp.erl b/lib/compiler/src/core_pp.erl
index 03801a9b6d..01922c3fdf 100644
--- a/lib/compiler/src/core_pp.erl
+++ b/lib/compiler/src/core_pp.erl
@@ -184,12 +184,12 @@ format_1(#c_map{arg=Var,es=Es}, Ctxt) ->
     ];
 format_1(#c_map_pair{op=#c_literal{val=assoc},key=K,val=V}, Ctxt) ->
     ["::<",
-     format_hseq([K,V], ",", add_indent(Ctxt, 1), fun format/2),
+     format_map_pair(K, V, Ctxt),
      ">"
     ];
 format_1(#c_map_pair{op=#c_literal{val=exact},key=K,val=V}, Ctxt) ->
     ["~<",
-     format_hseq([K,V], ",", add_indent(Ctxt, 1), fun format/2),
+     format_map_pair(K, V, Ctxt),
      ">"
     ];
 format_1(#c_cons{hd=H,tl=T}, Ctxt) ->
@@ -448,6 +448,12 @@ format_list_tail(#c_cons{anno=[],hd=H,tl=T}, Ctxt) ->
 format_list_tail(Tail, Ctxt) ->
     ["|",format(Tail, add_indent(Ctxt, 1)),"]"].
 
+format_map_pair(K, V, Ctxt0) ->
+    Ctxt1 = add_indent(Ctxt0, 1),
+    Txt = format(K, set_class(Ctxt1, expr)),
+    Ctxt2 = add_indent(Ctxt0, width(Txt, Ctxt1)),
+    [Txt,",",format(V, Ctxt2)].
+
 indent(Ctxt) -> indent(Ctxt#ctxt.indent, Ctxt).
 
 indent(N, _) when N =< 0 -> "";
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index f3e90f8eb2..ba46adfbc6 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -313,7 +313,7 @@ expr(#c_letrec{defs=Fs0,body=B0}=Letrec, Ctxt, Sub) ->
     Fs1 = map(fun ({Name,Fb}) ->
 		      {Name,expr(Fb, {letrec,Ctxt}, Sub)}
 	      end, Fs0),
-    B1 = body(B0, value, Sub),
+    B1 = body(B0, Ctxt, Sub),
     Letrec#c_letrec{defs=Fs1,body=B1};
 expr(#c_case{}=Case0, Ctxt, Sub) ->
     %% Ideally, the compiler should only emit warnings when there is
@@ -607,14 +607,6 @@ eval_binary_1([#c_bitstr{val=#c_literal{val=Val},size=#c_literal{val=Sz},
 	error:_ ->
 	    throw(impossible)
     end;
-eval_binary_1([#c_bitstr{val=#c_literal{},size=#c_literal{},
-			 unit=#c_literal{},type=#c_literal{},
-			 flags=#c_cons{}=Flags}=Bitstr|Ss], Acc0) ->
-    case cerl:fold_literal(Flags) of
-	#c_literal{} = Flags1 ->
-	    eval_binary_1([Bitstr#c_bitstr{flags=Flags1}|Ss], Acc0);
-	_ -> throw(impossible)
-    end;
 eval_binary_1([], Acc) -> Acc;
 eval_binary_1(_, _) -> throw(impossible).
 
diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 612660c2d6..a9b54005d1 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -105,7 +105,8 @@
 -record(iset,      {anno=#a{},var,arg}).
 -record(itry,      {anno=#a{},args,vars,body,evars,handler}).
 -record(ifilter,   {anno=#a{},arg}).
--record(igen,      {anno=#a{},acc_pat,acc_guard,skip_pat,tail,tail_pat,arg}).
+-record(igen,      {anno=#a{},ceps=[],acc_pat,acc_guard,
+		    skip_pat,tail,tail_pat,arg}).
 
 -type iapply()    :: #iapply{}.
 -type ibinary()   :: #ibinary{}.
@@ -535,7 +536,7 @@ expr({tuple,L,Es0}, St0) ->
     A = record_anno(L, St1),
     {annotate_tuple(A, Es1, St1),Eps,St1};
 expr({map,L,Es0}, St0) ->
-    map_build_pair_chain(#c_literal{val=#{}},Es0,lineno_anno(L,St0),St0);
+    map_build_pairs(#c_literal{val=#{}}, Es0, lineno_anno(L, St0), St0);
 expr({map,L,M0,Es0}, St0) ->
     try expr_map(M0,Es0,lineno_anno(L, St0),St0) of
 	{_,_,_}=Res -> Res
@@ -778,66 +779,35 @@ expr_map(M0,Es0,A,St0) ->
 		    Fc = fail_clause([Fpat], A, #c_literal{val=badarg}),
 		    {#icase{anno=#a{anno=A},args=[M1],clauses=Cs,fc=Fc},Mps,St3};
 		{_,_} ->
-		    {M2,Eps,St2} = map_build_pair_chain(M1,Es0,A,St1),
+		    {M2,Eps,St2} = map_build_pairs(M1, Es0, A, St1),
 		    {M2,Mps++Eps,St2}
 	    end;
 	false -> throw({bad_map,bad_map})
     end.
 
-%% Group continuous literal blocks and single variables, i.e.
-%% M0#{ a := 1, b := V1, K1 := V2, K2 := 42}
-%% becomes equivalent to
-%% M1 = M0#{ a := 1, b := V1 },
-%% M2 = M1#{ K1 := V1 },
-%% M3 = M2#{ K2 := 42 }
-
-map_build_pair_chain(M,Es,A,St) ->
-    %% hack, remove iset if only literal
-    case map_build_pair_chain(M,Es,A,St,[]) of
-	{_,[#iset{arg=#c_literal{}=Val}],St1} -> {Val,[],St1};
-	Normal -> Normal
+map_build_pairs(Map0, Es0, Ann, St0) ->
+    {Es,Pre,St1} = map_build_pairs_1(Es0, St0),
+    case ann_c_map(Ann, Map0, Es) of
+	#c_literal{}=Map ->
+	    {Map,[],St1};
+	#c_map{}=Map ->
+	    {Var,St2} = new_var(St1),
+	    {Var,Pre++[#iset{var=Var,arg=Map}],St2}
     end.
 
-map_build_pair_chain(M0,[],_,St,Mps) ->
-    {M0,Mps,St};
-map_build_pair_chain(M0,Es0,A,St0,Mps) ->
-    % group continuous literal blocks
-    % Anno = #a{anno=[compiler_generated]},
-    % order is important, we need to reverse the literals
-    case map_pair_block(Es0,[],[],St0) of
-	{{CesL,EspL},{[],[]},Es1,St1} ->
-	    {MVar,St2} = new_var(St1),
-	    Pre = [#iset{var=MVar, arg=ann_c_map(A,M0,reverse(CesL))}],
-	    map_build_pair_chain(MVar,Es1,A,St2,Mps++EspL++Pre);
-	{{[],[]},{CesV,EspV},Es1,St1} ->
-	    {MVar,St2} = new_var(St1),
-	    Pre = [#iset{var=MVar, arg=#c_map{arg=M0,es=CesV, anno=A}}],
-	    map_build_pair_chain(MVar,Es1,A,St2,Mps ++ EspV++Pre);
-	{{CesL,EspL},{CesV,EspV},Es1,St1} ->
-	    {MVarL,St2} = new_var(St1),
-	    {MVarV,St3} = new_var(St2),
-	    Pre = [#iset{var=MVarL, arg=ann_c_map(A,M0,reverse(CesL))},
-		   #iset{var=MVarV, arg=#c_map{arg=MVarL,es=CesV,anno=A}}],
-	    map_build_pair_chain(MVarV,Es1,A,St3,Mps++EspL++EspV++Pre)
-    end.
-
-map_pair_block([{Op,L,K0,V0}|Es],Ces,Esp,St0) ->
-    {K,Ep0,St1} = safe(K0, St0),
-    {V,Ep1,St2} = safe(V0, St1),
-    A = lineno_anno(L, St2),
-    Pair0 = map_op_to_c_map_pair(Op),
-    Pair1 = Pair0#c_map_pair{anno=A,key=K,val=V},
-    case cerl:is_literal(K) of
-	true ->
-	    map_pair_block(Es,[Pair1|Ces],Ep0 ++ Ep1 ++ Esp,St2);
-	false ->
-	    {{Ces,Esp},{[Pair1],Ep0++Ep1},Es,St2}
-    end;
-map_pair_block([],Ces,Esp,St) ->
-    {{Ces,Esp},{[],[]},[],St}.
+map_build_pairs_1([{Op0,L,K0,V0}|Es], St0) ->
+    {K,Pre0,St1} = safe(K0, St0),
+    {V,Pre1,St2} = safe(V0, St1),
+    {Pairs,Pre2,St3} = map_build_pairs_1(Es, St2),
+    As = lineno_anno(L, St3),
+    Op = map_op(Op0),
+    Pair = cerl:ann_c_map_pair(As, Op, K, V),
+    {[Pair|Pairs],Pre0++Pre1++Pre2,St3};
+map_build_pairs_1([], St) ->
+    {[],[],St}.
 
-map_op_to_c_map_pair(map_field_assoc) -> #c_map_pair{op=#c_literal{val=assoc}};
-map_op_to_c_map_pair(map_field_exact) -> #c_map_pair{op=#c_literal{val=exact}}.
+map_op(map_field_assoc) -> #c_literal{val=assoc};
+map_op(map_field_exact) -> #c_literal{val=exact}.
 
 is_valid_map_src(#c_literal{val = M}) when is_map(M) -> true;
 is_valid_map_src(#c_var{})  -> true;
@@ -1011,7 +981,8 @@ fun_tq({_,_,Name}=Id, Cs0, L, St0, NameInfo) ->
 %% lc_tq(Line, Exp, [Qualifier], Mc, State) -> {LetRec,[PreExp],State}.
 %%  This TQ from Simon PJ pp 127-138.  
 
-lc_tq(Line, E, [#igen{anno=GAnno,acc_pat=AccPat,acc_guard=AccGuard,
+lc_tq(Line, E, [#igen{anno=GAnno,ceps=Ceps,
+		      acc_pat=AccPat,acc_guard=AccGuard,
                       skip_pat=SkipPat,tail=Tail,tail_pat=TailPat,
                       arg={Pre,Arg}}|Qs], Mc, St0) ->
     {Name,St1} = new_fun_name("lc", St0),
@@ -1046,7 +1017,7 @@ lc_tq(Line, E, [#igen{anno=GAnno,acc_pat=AccPat,acc_guard=AccGuard,
     Fun = #ifun{anno=LAnno,id=[],vars=[Var],clauses=Cs,fc=Fc},
     {#iletrec{anno=LAnno#a{anno=[list_comprehension|LA]},defs=[{{Name,1},Fun}],
               body=Pre ++ [#iapply{anno=LAnno,op=F,args=[Arg]}]},
-     [],St4};
+     Ceps,St4};
 lc_tq(Line, E, [#ifilter{}=Filter|Qs], Mc, St) ->
     filter_tq(Line, E, Filter, Mc, St, Qs, fun lc_tq/5);
 lc_tq(Line, E0, [], Mc0, St0) ->
@@ -1071,7 +1042,8 @@ bc_tq(Line, Exp, Qs0, _, St0) ->
 			    args=[Sz]}}] ++ BcPre,
     {E,Pre,St}.
 
-bc_tq1(Line, E, [#igen{anno=GAnno,acc_pat=AccPat,acc_guard=AccGuard,
+bc_tq1(Line, E, [#igen{anno=GAnno,ceps=Ceps,
+		       acc_pat=AccPat,acc_guard=AccGuard,
                        skip_pat=SkipPat,tail=Tail,tail_pat=TailPat,
                        arg={Pre,Arg}}|Qs], Mc, St0) ->
     {Name,St1} = new_fun_name("lbc", St0),
@@ -1109,7 +1081,7 @@ bc_tq1(Line, E, [#igen{anno=GAnno,acc_pat=AccPat,acc_guard=AccGuard,
     Fun = #ifun{anno=LAnno,id=[],vars=Vars,clauses=Cs,fc=Fc},
     {#iletrec{anno=LAnno#a{anno=[list_comprehension|LA]},defs=[{{Name,2},Fun}],
               body=Pre ++ [#iapply{anno=LAnno,op=F,args=[Arg,Mc]}]},
-     [],St4};
+     Ceps,St4};
 bc_tq1(Line, E, [#ifilter{}=Filter|Qs], Mc, St) ->
     filter_tq(Line, E, Filter, Mc, St, Qs, fun bc_tq1/5);
 bc_tq1(_, {bin,Bl,Elements}, [], AccVar, St0) ->
@@ -1245,8 +1217,9 @@ generator(Line, {generate,Lg,P0,E}, Gs, St0) ->
                                 ann_c_cons(LA, Skip, Tail)}
                        end,
     {Ce,Pre,St4} = safe(E, St3),
-    Gen = #igen{anno=#a{anno=GA},acc_pat=AccPat,acc_guard=Cg,skip_pat=SkipPat,
-                tail=Tail,tail_pat=#c_literal{anno=LA,val=[]},arg={Ceps++Pre,Ce}},
+    Gen = #igen{anno=#a{anno=GA},ceps=Ceps,
+		acc_pat=AccPat,acc_guard=Cg,skip_pat=SkipPat,
+                tail=Tail,tail_pat=#c_literal{anno=LA,val=[]},arg={Pre,Ce}},
     {Gen,St4};
 generator(Line, {b_generate,Lg,P,E}, Gs, St0) ->
     LA = lineno_anno(Line, St0),
@@ -1634,7 +1607,7 @@ pattern({tuple,L,Ps}, St) ->
     {annotate_tuple(record_anno(L, St), Ps1, St),Eps,St1};
 pattern({map,L,Pairs}, St0) ->
     {Ps,Eps,St1} = pattern_map_pairs(Pairs, St0),
-    {#c_map{anno=lineno_anno(L, St1), es=Ps},Eps,St1};
+    {#c_map{anno=lineno_anno(L, St1),es=Ps,is_pat=true},Eps,St1};
 pattern({bin,L,Ps}, St) ->
     %% We don't create a #ibinary record here, since there is
     %% no need to hold any used/new annotations in a pattern.
diff --git a/lib/compiler/src/v3_kernel.erl b/lib/compiler/src/v3_kernel.erl
index 6504351c02..72e7a39333 100644
--- a/lib/compiler/src/v3_kernel.erl
+++ b/lib/compiler/src/v3_kernel.erl
@@ -521,62 +521,76 @@ is_valid_map_src(#k_var{}) -> true;
 is_valid_map_src(_) -> false.
 
 map_split_pairs(A, Var, Ces, Sub, St0) ->
-    %% two steps
-    %% 1. force variables
-    %% 2. remove multiples
-    Pairs0 = [{Op,K,V} || #c_map_pair{op=#c_literal{val=Op},key=K,val=V} <- Ces],
+    %% 1. Force variables.
+    %% 2. Group adjacent pairs with literal keys.
+    %% 3. Within each such group, remove multiple assignments to the same key.
+    %% 4. Partition each group according to operator ('=>' and ':=').
+    Pairs0 = [{Op,K,V} ||
+		 #c_map_pair{op=#c_literal{val=Op},key=K,val=V} <- Ces],
     {Pairs,Esp,St1} = foldr(fun
 	    ({Op,K0,V0}, {Ops,Espi,Sti0}) when Op =:= assoc; Op =:= exact ->
 		{K,Eps1,Sti1} = atomic(K0, Sub, Sti0),
 		{V,Eps2,Sti2} = atomic(V0, Sub, Sti1),
 		{[{Op,K,V}|Ops],Eps1 ++ Eps2 ++ Espi,Sti2}
 	end, {[],[],St0}, Pairs0),
-
-    case map_group_pairs(Pairs) of
-	{Assoc,[]} ->
-	    Kes = [#k_map_pair{key=K,val=V}||{_,{assoc,K,V}} <- Assoc],
-	    {#k_map{anno=A,op=assoc,var=Var,es=Kes},Esp,St1};
-	{[],Exact} ->
-	    Kes = [#k_map_pair{key=K,val=V}||{_,{exact,K,V}} <- Exact],
-	    {#k_map{anno=A,op=exact,var=Var,es=Kes},Esp,St1};
-	{Assoc,Exact} ->
-	    Kes1 = [#k_map_pair{key=K,val=V}||{_,{assoc,K,V}} <- Assoc],
-	    {Mvar,Em,St2} = force_atomic(#k_map{anno=A,op=assoc,var=Var,es=Kes1},St1),
-	    Kes2 = [#k_map_pair{key=K,val=V}||{_,{exact,K,V}} <- Exact],
-	    {#k_map{anno=A,op=exact,var=Mvar,es=Kes2},Esp ++ Em,St2}
-
+    map_split_pairs_1(A, Var, Pairs, Esp, St1).
+
+map_split_pairs_1(A, Map0, [{Op,Key,Val}|Pairs1]=Pairs0, Esp0, St0) ->
+    {Map1,Em,St1} = force_atomic(Map0, St0),
+    case Key of
+	#k_var{} ->
+	    %% Don't combine variable keys with other keys.
+	    Kes = [#k_map_pair{key=Key,val=Val}],
+	    Map = #k_map{anno=A,op=Op,var=Map1,es=Kes},
+	    map_split_pairs_1(A, Map, Pairs1, Esp0 ++ Em, St1);
+	_ ->
+	    %% Literal key. Split off all literal keys.
+	    {L,Pairs} = splitwith(fun({_,#k_var{},_}) -> false;
+				     ({_,_,_}) -> true
+				  end, Pairs0),
+	    {Map,Esp,St2} = map_group_pairs(A, Map1, L, Esp0 ++ Em, St1),
+	    map_split_pairs_1(A, Map, Pairs, Esp, St2)
+    end;
+map_split_pairs_1(_, Map, [], Esp, St0) ->
+    {Map,Esp,St0}.
+
+map_group_pairs(A, Var, Pairs0, Esp, St0) ->
+    Pairs = map_remove_dup_keys(Pairs0),
+    Assoc = [#k_map_pair{key=K,val=V} || {_,{assoc,K,V}} <- Pairs],
+    Exact = [#k_map_pair{key=K,val=V} || {_,{exact,K,V}} <- Pairs],
+    case {Assoc,Exact} of
+	{[_|_],[]} ->
+	    {#k_map{anno=A,op=assoc,var=Var,es=Assoc},Esp,St0};
+	{[],[_|_]} ->
+	    {#k_map{anno=A,op=exact,var=Var,es=Exact},Esp,St0};
+	{[_|_],[_|_]} ->
+	    Map = #k_map{anno=A,op=assoc,var=Var,es=Assoc},
+	    {Mvar,Em,St1} = force_atomic(Map, St0),
+	    {#k_map{anno=A,op=exact,var=Mvar,es=Exact},Esp ++ Em,St1}
     end.
 
-%% Group map by Assoc operations and Exact operations
-
-map_group_pairs(Es) ->
-    Groups = dict:to_list(map_group_pairs(Es,dict:new())),
-    partition(fun({_,{Op,_,_}}) -> Op =:= assoc end, Groups).
-
-map_group_pairs([{assoc,K,V}|Es0],Used0) ->
-    Used1 = case map_key_is_used(K,Used0) of
-	{ok, {assoc,_,_}} -> map_key_set_used(K,{assoc,K,V},Used0);
-	{ok, {exact,_,_}} -> map_key_set_used(K,{exact,K,V},Used0);
-	_                 -> map_key_set_used(K,{assoc,K,V},Used0)
-    end,
-    map_group_pairs(Es0,Used1);
-map_group_pairs([{exact,K,V}|Es0],Used0) ->
-    Used1 = case map_key_is_used(K,Used0) of
-	{ok, {assoc,_,_}} -> map_key_set_used(K,{assoc,K,V},Used0);
-	{ok, {exact,_,_}} -> map_key_set_used(K,{exact,K,V},Used0);
-	_                 -> map_key_set_used(K,{exact,K,V},Used0)
-    end,
-    map_group_pairs(Es0,Used1);
-map_group_pairs([],Used) ->
-    Used.
+map_remove_dup_keys(Es) ->
+    dict:to_list(map_remove_dup_keys(Es, dict:new())).
 
-map_key_set_used(K,How,Used) ->
-    dict:store(map_key_clean(K),How,Used).
-
-map_key_is_used(K,Used) ->
-    dict:find(map_key_clean(K),Used).
+map_remove_dup_keys([{assoc,K0,V}|Es0],Used0) ->
+    K = map_key_clean(K0),
+    Op = case dict:find(K, Used0) of
+	     {ok,{exact,_,_}} -> exact;
+	     _                -> assoc
+	 end,
+    Used1 = dict:store(K, {Op,K0,V}, Used0),
+    map_remove_dup_keys(Es0, Used1);
+map_remove_dup_keys([{exact,K0,V}|Es0],Used0) ->
+    K = map_key_clean(K0),
+    Op = case dict:find(K, Used0) of
+	     {ok,{assoc,_,_}} -> assoc;
+	     _                -> exact
+	 end,
+    Used1 = dict:store(K, {Op,K0,V}, Used0),
+    map_remove_dup_keys(Es0, Used1);
+map_remove_dup_keys([], Used) -> Used.
 
-%% Be explicit instead of using set_kanno(K,[])
+%% Be explicit instead of using set_kanno(K, []).
 map_key_clean(#k_var{name=V})    -> {var,V};
 map_key_clean(#k_literal{val=V}) -> {lit,V};
 map_key_clean(#k_int{val=V})     -> {lit,V};