[CSSimplify] Don't suppress existential opening if as any ... is in parens

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -1479,13 +1479,14 @@ shouldOpenExistentialCallArgument(
     return None;
 
   // An argument expression that explicitly coerces to an existential
-  // disables the implicit opening of the existential.
+  // disables the implicit opening of the existential unless it's
+  // wrapped in parens.
   if (argExpr) {
     if (auto argCast = dyn_cast<ExplicitCastExpr>(
             argExpr->getSemanticsProvidingExpr())) {
       if (auto typeRepr = argCast->getCastTypeRepr()) {
         if (auto toType = cs.getType(typeRepr)) {
-          if (toType->isAnyExistentialType())
+          if (!isa<ParenExpr>(argExpr) && toType->isAnyExistentialType())
             return None;
         }
       }

test/Constraints/opened_existentials.swift

@@ -288,6 +288,6 @@ func testExplicitCoercionRequirement(v: any B, otherV: any B & D) {
   getP(getC(v)) // expected-error {{inferred result type 'any P' requires explicit coercion due to loss of generic requirements}} {{8-8=(}} {{15-15=as any P)}}
   getP(v.getC()) // expected-error {{inferred result type 'any P' requires explicit coercion due to loss of generic requirements}}  {{8-8=(}} {{14-14=as any P)}}
 
-  getP((getC(v) as any P)) // Ok - parens avoid opening suppression
-
+  getP((getC(v) as any P))   // Ok - parens avoid opening suppression
+  getP((v.getC() as any P))  // Ok - parens avoid opening suppression
 }