Generalize optimizations of case statements

Case expressions such as:

  case {Expr1,Expr} of
     {V1,V2} -> ...
  end

are already optimized to not actually build the tuple. Generalize
the optimization to avoid building any kind of composite term,
such as:

  case {ok,[A,B]} of
    {ok,[X,Y]} -> ...
  end

We don't expect programmers to write such code directly, but
inlining can produce such code.

We need to be careful about the warnings we produce. If the case
expression is a literal, it is expected that no warnings should be
produced for clauses that don't match. We must make sure that we
continue to suppress those warnings.

2 files changed, 10 insertions, 0 deletions

diff --git a/lib/compiler/test/core_fold_SUITE.erl b/lib/compiler/test/core_fold_SUITE.erl
index a5a4e62a42..69f61a046f 100644
--- a/lib/compiler/test/core_fold_SUITE.erl
+++ b/lib/compiler/test/core_fold_SUITE.erl
@@ -249,6 +249,12 @@ coverage(Config) when is_list(Config) ->
     case list_to_pid("<0.42.0>") of
 	Pid when is_pid(Pid) -> ok
     end,
+
+    %% Cover the non-variable case in bsm_do_an/4.
+    ok = bsm_an_inlined(<<1>>, Config),
+    error = bsm_an_inlined(<<1,2,3>>, Config),
+    error = bsm_an_inlined([], Config),
+
     ok.
 
 cover_will_match_list_type(A) ->
@@ -290,6 +296,9 @@ cover_is_safe_bool_expr(X) ->
 	    false
     end.
 
+bsm_an_inlined(<<_:8>>, _) -> ok;
+bsm_an_inlined(_, _) -> error.
+
 id(I) -> I.
 
 unused_multiple_values_error(Config) when is_list(Config) ->
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index 810b2b48c9..7186956603 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -117,6 +117,7 @@ pattern2(Config) when is_list(Config) ->
 	   Source,
 	   [nowarn_unused_vars],
 	   {warnings,[{2,sys_core_fold,{nomatch_shadow,1}},
+		      {4,sys_core_fold,no_clause_match},
 		      {5,sys_core_fold,nomatch_clause_type},
 		      {6,sys_core_fold,nomatch_clause_type}]}}],
     ?line [] = run(Config, Ts),