[Sema] Prevent duplicate diagnostics for opaque return type

Author: angela-laar

lib/Sema/TypeCheckGeneric.cpp

@@ -79,6 +79,7 @@ OpaqueResultTypeRequest::evaluate(Evaluator &evaluator,
         .diagnose(repr->getLoc(), diag::opaque_type_in_protocol_requirement)
         .fixItInsert(fixitLoc, result)
         .fixItReplace(repr->getSourceRange(), placeholder);
+    repr->setInvalid();
 
     return nullptr;
   }
@@ -162,6 +163,7 @@ OpaqueResultTypeRequest::evaluate(Evaluator &evaluator,
              .diagnose(currentRepr->getLoc(), diag::opaque_of_optional_rewrite)
              .fixItReplaceChars(currentRepr->getStartLoc(),
                                 currentRepr->getEndLoc(), stream.str());
+          repr->setInvalid();
           return nullptr;
         }
       }
@@ -199,6 +201,7 @@ OpaqueResultTypeRequest::evaluate(Evaluator &evaluator,
         // Error out if the constraint type isn't a class or existential type.
         ctx.Diags.diagnose(currentRepr->getLoc(),
                            diag::opaque_type_invalid_constraint);
+        currentRepr->setInvalid();
         return nullptr;
       }
 
@@ -246,6 +249,7 @@ OpaqueResultTypeRequest::evaluate(Evaluator &evaluator,
         ctx.Diags.diagnose(repr->getLoc(),
                            diag::opaque_type_in_parameter,
                            false, interfaceType);
+        repr->setInvalid();
         return true;
       }
     }

lib/Sema/TypeCheckType.cpp

@@ -2278,8 +2278,10 @@ NeverNullType TypeResolver::resolveType(TypeRepr *repr,
     bool isInExistential = diagnoseDisallowedExistential(opaqueRepr);
 
     if (auto opaqueDecl = dyn_cast<OpaqueTypeDecl>(DC)) {
-      if (auto ordinal = opaqueDecl->getAnonymousOpaqueParamOrdinal(opaqueRepr))
-        return getIdentityOpaqueTypeArchetypeType(opaqueDecl, *ordinal);
+      if (auto ordinal = opaqueDecl->getAnonymousOpaqueParamOrdinal(opaqueRepr)){
+        if(!isInExistential)
+          return getIdentityOpaqueTypeArchetypeType(opaqueDecl, *ordinal);
+      }
     }
 
     // Check whether any of the generic parameters in the context represents
@@ -2295,7 +2297,7 @@ NeverNullType TypeResolver::resolveType(TypeRepr *repr,
       }
     }
 
-    if (!isInExistential){
+    if (!repr->isInvalid()){
       // We are not inside an `OpaqueTypeDecl`, so diagnose an error.
       if (!(options & TypeResolutionFlags::SilenceErrors)) {
         diagnose(opaqueRepr->getOpaqueLoc(),
@@ -4515,6 +4517,7 @@ TypeResolver::resolveExistentialType(ExistentialTypeRepr *repr,
   if (constraintType->hasError())
     return ErrorType::get(getASTContext());
 
+  //TO-DO: generalize this and emit the same erorr for some P?
   if (!constraintType->isConstraintType()) {
     // Emit a tailored diagnostic for the incorrect optional
     // syntax 'any P?' with a fix-it to add parenthesis.