SILGen: Include more effects in function_conversion peephole.

Sometimes we emit a closure literal with escaping/nonthrowing/nonasync type
into a context that wants a nonescaping/throwing/async function, and it
ends up wrapped in a conversion. We can look through any of these and emit
the closure literal directly with those effects.

Author: jckarter

lib/SILGen/SILGenExpr.cpp

@@ -1754,11 +1754,26 @@ static bool canPeepholeLiteralClosureConversion(Type literalType,
     return true;
   }
 
-  // Does the conversion only add `throws`?
-  if (literalFnType->isEqual(convertedFnType->getWithoutThrowing())) {
+  // Are the types equivalent aside from effects (throws) or coeffects
+  // (escaping)? Then we should emit the literal as having the destination type
+  // (co)effects, even if it doesn't exercise them.
+  //
+  // TODO: We could also in principle let `async` through here, but that
+  // interferes with the implementation of `reasync`.
+  auto literalWithoutEffects = literalFnType->getExtInfo().intoBuilder()
+    .withThrows(false)
+    .withNoEscape(false)
+    .build();
+    
+  auto convertedWithoutEffects = convertedFnType->getExtInfo().intoBuilder()
+    .withThrows(false)
+    .withNoEscape(false)
+    .build();
+  if (literalFnType->withExtInfo(literalWithoutEffects)
+        ->isEqual(convertedFnType->withExtInfo(convertedWithoutEffects))) {
     return true;
   }
-  
+
   return false;
 }
 

test/SILGen/closure_literal_reabstraction.swift

@@ -24,3 +24,11 @@ func reabstractCaptureListExprArgument() {
 func reabstractKeyPathFunctionArgument() {
     gen(f: \Butt.x)
 }
+
+// CHECK-LABEL: sil {{.*}} @{{.*}}reabstractStaticMemberRef
+// CHECK:         [[CLOSURE_FN:%.*]] = function_ref {{.*}}u_
+// CHECK:         [[CLOSURE:%.*]] = thin_to_thick_function [[CLOSURE_FN]]
+// CHECK:         apply {{.*}}<Int, Butt>([[CLOSURE]])
+func reabstractStaticMemberRef() {
+    gen(f: Butt.init)
+}

test/SILOptimizer/closure_lifetime_fixup.swift

@@ -95,15 +95,10 @@ public func dontCrash<In, Out>(test: Bool, body: @escaping ((In) -> Out, In) ->
 }
 
 // CHECK-LABEL: sil @$s22closure_lifetime_fixup28to_stack_of_convert_function1pySvSg_tF
-// CHECK:  [[FN:%.*]] = function_ref @$s22closure_lifetime_fixup28to_stack_of_convert_function1pySvSg_tFSSSvcfu_ : $@convention(thin) (UnsafeMutableRawPointer) -> @owned String
+// CHECK:  [[FN:%.*]] = function_ref @$s22closure_lifetime_fixup28to_stack_of_convert_function1pySvSg_tFSSSvcfu_ :
 // CHECK:  [[PA:%.*]] = thin_to_thick_function [[FN]]
-// CHECK:  [[CVT:%.*]] = convert_function [[PA]]
-// CHECK:  [[CVT2:%.*]] = convert_escape_to_noescape [[CVT]]
-// CHECK:  [[REABSTRACT:%.*]] = function_ref @$sSvSSs5Error_pIgyozo_SvSSsAA_pIegnrzo_TR
-// CHECK:  [[PA2:%.*]] = partial_apply [callee_guaranteed] [on_stack] [[REABSTRACT]]([[CVT2]])
-// CHECK:  [[CF2:%.*]] = convert_function [[PA2]]
 // CHECK:  [[MAP:%.*]] = function_ref @$sSq3mapyqd__Sgqd__xKXEKlF
-// CHECK:  try_apply [[MAP]]<UnsafeMutableRawPointer, String>({{.*}}, [[CF2]], {{.*}})
+// CHECK:  try_apply [[MAP]]<UnsafeMutableRawPointer, String>({{.*}}, [[PA]], {{.*}})
 public func to_stack_of_convert_function(p: UnsafeMutableRawPointer?) {
   _ = p.map(String.init(describing:))
 }