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

14 files changed, 352 insertions, 237 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};
diff --git a/lib/compiler/test/compile_SUITE.erl b/lib/compiler/test/compile_SUITE.erl
index 0ff03c4295..1c96abe017 100644
--- a/lib/compiler/test/compile_SUITE.erl
+++ b/lib/compiler/test/compile_SUITE.erl
@@ -748,42 +748,65 @@ env_1(Simple, Target) ->
 %% compile the generated Core Erlang files.
 
 core(Config) when is_list(Config) ->
-    ?line Dog = test_server:timetrap(test_server:minutes(5)),
-    ?line PrivDir = ?config(priv_dir, Config),
-    ?line Outdir = filename:join(PrivDir, "core"),
-    ?line ok = file:make_dir(Outdir),
+    PrivDir = ?config(priv_dir, Config),
+    Outdir = filename:join(PrivDir, "core"),
+    ok = file:make_dir(Outdir),
 
-    ?line Wc = filename:join(filename:dirname(code:which(?MODULE)), "*.beam"),
-    ?line TestBeams = filelib:wildcard(Wc),
-    ?line Abstr = [begin {ok,{Mod,[{abstract_code,
+    Wc = filename:join(filename:dirname(code:which(?MODULE)), "*.beam"),
+    TestBeams = filelib:wildcard(Wc),
+    Abstr = [begin {ok,{Mod,[{abstract_code,
 				    {raw_abstract_v1,Abstr}}]}} = 
 			     beam_lib:chunks(Beam, [abstract_code]),
 			 {Mod,Abstr} end || Beam <- TestBeams],
-    ?line Res = test_lib:p_run(fun(F) -> do_core(F, Outdir) end, Abstr),
-    ?line test_server:timetrap_cancel(Dog),
-    Res.
-
+    test_lib:p_run(fun(F) -> do_core(F, Outdir) end, Abstr).
     
 do_core({M,A}, Outdir) ->
     try
-	{ok,M,Core} = compile:forms(A, [to_core,report]),
-	CoreFile = filename:join(Outdir, atom_to_list(M)++".core"),
-	CorePP = core_pp:format(Core),
-	ok = file:write_file(CoreFile, CorePP),
-	case compile:file(CoreFile, [clint,from_core,binary]) of
-	    {ok,M,_} ->
-		ok = file:delete(CoreFile);
-	    Other ->
-		io:format("*** core_lint failure '~p' for ~s\n",
-			  [Other,CoreFile]),
-		error
-	end
-    catch Class:Error ->
+	do_core_1(M, A, Outdir)
+    catch
+	throw:{error,Error} ->
+	    io:format("*** compilation failure '~p' for module ~s\n",
+		      [Error,M]),
+	    error;
+	Class:Error ->
 	    io:format("~p: ~p ~p\n~p\n",
 		      [M,Class,Error,erlang:get_stacktrace()]),
 	    error
     end.
 
+do_core_1(M, A, Outdir) ->
+    {ok,M,Core0} = compile:forms(A, [to_core]),
+    CoreFile = filename:join(Outdir, atom_to_list(M)++".core"),
+    CorePP = core_pp:format(Core0),
+    ok = file:write_file(CoreFile, CorePP),
+
+    %% Parse the .core file and return the result as Core Erlang Terms.
+    Core = case compile:file(CoreFile, [report_errors,from_core,no_copt,to_core,binary]) of
+	       {ok,M,Core1} -> Core1;
+	       Other -> throw({error,Other})
+	   end,
+    ok = file:delete(CoreFile),
+
+    %% Compile as usual (including optimizations).
+    compile_forms(Core, [clint,from_core,binary]),
+
+    %% Don't optimize to test that we are not dependent
+    %% on the Core Erlang optmimization passes.
+    %% (Example of a previous bug: The core_parse pass
+    %% would not turn map literals into #c_literal{}
+    %% records; if sys_core_fold was run it would fix
+    %% that; if sys_core_fold was not run v3_kernel would
+    %% crash.)
+    compile_forms(Core, [clint,from_core,no_copt,binary]),
+
+    ok.
+
+compile_forms(Forms, Opts) ->
+    case compile:forms(Forms, [report_errors|Opts]) of
+	{ok,[],_} ->  ok;
+	Other -> throw({error,Other})
+    end.
+
 %% Compile to Beam assembly language (.S) and then try to
 %% run .S through the compiler again.
 
diff --git a/lib/compiler/test/lc_SUITE.erl b/lib/compiler/test/lc_SUITE.erl
index 398398a397..6c5b34498b 100644
--- a/lib/compiler/test/lc_SUITE.erl
+++ b/lib/compiler/test/lc_SUITE.erl
@@ -18,12 +18,12 @@
 %%
 -module(lc_SUITE).
 
--author('[email protected]').
 -export([all/0, suite/0,groups/0,init_per_suite/1, end_per_suite/1, 
 	 init_per_group/2,end_per_group/2,
 	 init_per_testcase/2,end_per_testcase/2,
 	 basic/1,deeply_nested/1,no_generator/1,
-	 empty_generator/1,no_export/1]).
+	 empty_generator/1,no_export/1,shadow/1,
+	 effect/1]).
 
 -include_lib("test_server/include/test_server.hrl").
 
@@ -31,10 +31,18 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
 
 all() -> 
     test_lib:recompile(?MODULE),
-    [basic, deeply_nested, no_generator, empty_generator, no_export].
+    [{group,p}].
 
 groups() -> 
-    [].
+    [{p,test_lib:parallel(),
+      [basic,
+       deeply_nested,
+       no_generator,
+       empty_generator,
+       no_export,
+       shadow,
+       effect
+      ]}].
 
 init_per_suite(Config) ->
     Config.
@@ -59,34 +67,34 @@ end_per_testcase(Case, Config) when is_atom(Case), is_list(Config) ->
     ok.
 
 basic(Config) when is_list(Config) ->
-    ?line L0 = lists:seq(1, 10),
-    ?line L1 = my_map(fun(X) -> {x,X} end, L0),
-    ?line L1 = [{x,X} || X <- L0],
-    ?line L0 = my_map(fun({x,X}) -> X end, L1),
-    ?line [1,2,3,4,5] = [X || X <- L0, X < 6],
-    ?line [4,5,6] = [X || X <- L0, X > 3, X < 7],
-    ?line [] = [X || X <- L0, X > 32, X < 7],
-    ?line [1,3,5,7,9] = [X || X <- L0, odd(X)],
-    ?line [2,4,6,8,10] = [X || X <- L0, not odd(X)],
-    ?line [1,3,5,9] = [X || X <- L0, odd(X), X =/= 7],
-    ?line [2,4,8,10] = [X || X <- L0, not odd(X), X =/= 6],
+    L0 = lists:seq(1, 10),
+    L1 = my_map(fun(X) -> {x,X} end, L0),
+    L1 = [{x,X} || X <- L0],
+    L0 = my_map(fun({x,X}) -> X end, L1),
+    [1,2,3,4,5] = [X || X <- L0, X < 6],
+    [4,5,6] = [X || X <- L0, X > 3, X < 7],
+    [] = [X || X <- L0, X > 32, X < 7],
+    [1,3,5,7,9] = [X || X <- L0, odd(X)],
+    [2,4,6,8,10] = [X || X <- L0, not odd(X)],
+    [1,3,5,9] = [X || X <- L0, odd(X), X =/= 7],
+    [2,4,8,10] = [X || X <- L0, not odd(X), X =/= 6],
 
     %% Append is specially handled.
-    ?line [1,3,5,9,2,4,8,10] = [X || X <- L0, odd(X), X =/= 7] ++
+    [1,3,5,9,2,4,8,10] = [X || X <- L0, odd(X), X =/= 7] ++
 	[X || X <- L0, not odd(X), X =/= 6],
 
     %% Guards BIFs are evaluated in guard context. Weird, but true.
-    ?line [{a,b,true},{x,y,true,true}] = [X || X <- tuple_list(), element(3, X)],
+    [{a,b,true},{x,y,true,true}] = [X || X <- tuple_list(), element(3, X)],
 
     %% Filter expressions with andalso/orelse.
-    ?line "abc123" = alphanum("?abc123.;"),
+    "abc123" = alphanum("?abc123.;"),
 
     %% Error cases.
-    ?line [] = [{xx,X} || X <- L0, element(2, X) == no_no_no],
-    ?line {'EXIT',_} = (catch [X || X <- L1, list_to_atom(X) == dum]),
-    ?line [] = [X || X <- L1, X+1 < 2],
-    ?line {'EXIT',_} = (catch [X || X <- L1, odd(X)]),
-    ?line fc([x], catch [E || E <- id(x)]),
+    [] = [{xx,X} || X <- L0, element(2, X) == no_no_no],
+    {'EXIT',_} = (catch [X || X <- L1, list_to_atom(X) == dum]),
+    [] = [X || X <- L1, X+1 < 2],
+    {'EXIT',_} = (catch [X || X <- L1, odd(X)]),
+    fc([x], catch [E || E <- id(x)]),
     ok.
 
 tuple_list() ->
@@ -116,12 +124,12 @@ deeply_nested_1() ->
 	X16 <- [4],X17 <- [3],X18 <- [fun() -> X16+X17 end],X19 <- [2],X20 <- [1]].
 
 no_generator(Config) when is_list(Config) ->
-    ?line Seq = lists:seq(-10, 17),
-    ?line [no_gen_verify(no_gen(A, B), A, B) || A <- Seq, B <- Seq],
+    Seq = lists:seq(-10, 17),
+    [no_gen_verify(no_gen(A, B), A, B) || A <- Seq, B <- Seq],
 
     %% Literal expression, for coverage.
-    ?line [a] = [a || true],
-    ?line [a,b,c] = [a || true] ++ [b,c],
+    [a] = [a || true],
+    [a,b,c] = [a || true] ++ [b,c],
     ok.
 
 no_gen(A, B) ->    
@@ -174,13 +182,40 @@ no_gen_eval(Fun, Res) ->
 no_gen_one_more(A, B) -> A + 1 =:= B.
 
 empty_generator(Config) when is_list(Config) ->
-    ?line [] = [X || {X} <- [], (false or (X/0 > 3))],
+    [] = [X || {X} <- [], (false or (X/0 > 3))],
     ok.
 
 no_export(Config) when is_list(Config) ->
     [] = [ _X = a || false ] ++ [ _X = a || false ],
     ok.
 
+%% Test that variables in list comprehensions are
+%% correctly shadowed.
+
+shadow(Config) when is_list(Config) ->
+    Shadowed = nomatch,
+    _ = id(Shadowed),				%Eliminate warning.
+    L = [{Shadowed,Shadowed+1} || Shadowed <- lists:seq(7, 9)],
+    [{7,8},{8,9},{9,10}] = id(L),
+    [8,9] = id([Shadowed || {_,Shadowed} <- id(L),
+			    Shadowed < 10]),
+    ok.
+
+effect(Config) when is_list(Config) ->
+    [{42,{a,b,c}}] =
+	do_effect(fun(F, L) ->
+			  [F({V1,V2}) ||
+			      #{<<1:500>>:=V1,<<2:301>>:=V2} <- L],
+			  ok
+		  end, id([#{},x,#{<<1:500>>=>42,<<2:301>>=>{a,b,c}}])),
+    ok.
+
+do_effect(Lc, L) ->
+    put(?MODULE, []),
+    F = fun(V) -> put(?MODULE, [V|get(?MODULE)]) end,
+    ok = Lc(F, L),
+    lists:reverse(erase(?MODULE)).
+
 id(I) -> I.
     
 fc(Args, {'EXIT',{function_clause,[{?MODULE,_,Args,_}|_]}}) -> ok;
diff --git a/lib/compiler/test/map_SUITE.erl b/lib/compiler/test/map_SUITE.erl
index dbac61765b..bc5ae803c6 100644
--- a/lib/compiler/test/map_SUITE.erl
+++ b/lib/compiler/test/map_SUITE.erl
@@ -319,6 +319,12 @@ t_update_exact(Config) when is_list(Config) ->
     {'EXIT',{badarg,_}} = (catch M0#{42=>v1,42.0:=v2,42:=v3}),
     {'EXIT',{badarg,_}} = (catch <<>>#{nonexisting:=val}),
     {'EXIT',{badarg,_}} = (catch M0#{<<0:257>> := val}), %% limitation
+
+    %% A workaround for a bug allowed an empty map to be updated.
+    {'EXIT',{badarg,_}} = (catch (id(#{}))#{a:=1}),
+    {'EXIT',{badarg,_}} = (catch #{}#{a:=1}),
+    Empty = #{},
+    {'EXIT',{badarg,_}} = (catch Empty#{a:=1}),
     ok.
 
 t_update_values(Config) when is_list(Config) ->
diff --git a/lib/compiler/test/match_SUITE.erl b/lib/compiler/test/match_SUITE.erl
index 033988e4c8..74efed7588 100644
--- a/lib/compiler/test/match_SUITE.erl
+++ b/lib/compiler/test/match_SUITE.erl
@@ -22,7 +22,8 @@
 	 init_per_group/2,end_per_group/2,
 	 pmatch/1,mixed/1,aliases/1,match_in_call/1,
 	 untuplify/1,shortcut_boolean/1,letify_guard/1,
-	 selectify/1,underscore/1,match_map/1,coverage/1]).
+	 selectify/1,underscore/1,match_map/1,map_vars_used/1,
+      coverage/1]).
 	 
 -include_lib("test_server/include/test_server.hrl").
 
@@ -36,7 +37,7 @@ groups() ->
     [{p,[parallel],
       [pmatch,mixed,aliases,match_in_call,untuplify,
        shortcut_boolean,letify_guard,selectify,
-       underscore,match_map,coverage]}].
+       underscore,match_map,map_vars_used,coverage]}].
 
 
 init_per_suite(Config) ->
@@ -412,6 +413,19 @@ do_match_map(#s{map=#{key:=Val}}=S) ->
     %% Would crash with a 'badarg' exception.
     S#s{t=Val}.
 
+map_vars_used(Config) when is_list(Config) ->
+    {some,value} = do_map_vars_used(a, b, #{{a,b}=>42,v=>{some,value}}),
+    ok.
+
+do_map_vars_used(X, Y, Map) ->
+    case {X,Y} of
+	T ->
+	    %% core_lib:is_var_used/2 would not consider T used.
+	    #{T:=42,v:=Val} = Map,
+	    Val
+    end.
+
+
 coverage(Config) when is_list(Config) ->
     %% Cover beam_dead.
     ok = coverage_1(x, a),
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index be0348a92d..6e5a7d35e9 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -699,10 +699,10 @@ run(Config, Tests) ->
 %% Compiles a test module and returns the list of errors and warnings.
 
 run_test(Conf, Test0, Warnings) ->
-    Mod = "warnings_"++test_lib:uniq(),
-    Filename = Mod ++ ".erl",
+    Module = "warnings_"++test_lib:uniq(),
+    Filename = Module ++ ".erl",
     ?line DataDir = ?privdir,
-    Test = ["-module(", Mod, "). ", Test0],
+    Test = ["-module(", Module, "). ", Test0],
     ?line File = filename:join(DataDir, Filename),
     ?line Opts = [binary,export_all,return|Warnings],
     ?line ok = file:write_file(File, Test),