Merge pull request swiftlang#31484 from CodaFi/opaque-results-may-vary

Propagate Failures Explicitly in Opaque Type Resolution

Author: CodaFi

lib/Sema/TypeCheckType.cpp

@@ -2657,17 +2657,21 @@ Type TypeResolver::resolveOpaqueReturnType(TypeRepr *repr,
   if (auto generic = dyn_cast<GenericIdentTypeRepr>(repr)) {
     for (auto argRepr : generic->getGenericArgs()) {
       auto argTy = resolveType(argRepr, options);
-      if (!argTy)
-        return Type();
+      // If we cannot resolve the generic parameter, propagate the error out.
+      if (!argTy || argTy->hasError()) {
+        return ErrorType::get(Context);
+      }
       TypeArgsBuf.push_back(argTy);
     }
   }
 
   // Use type reconstruction to summon the opaque type decl.
   Demangler demangle;
   auto definingDeclNode = demangle.demangleSymbol(mangledName);
-  if (!definingDeclNode)
-    return Type();
+  if (!definingDeclNode) {
+    diagnose(repr->getLoc(), diag::no_opaque_return_type_of);
+    return ErrorType::get(Context);
+  }
   if (definingDeclNode->getKind() == Node::Kind::Global)
     definingDeclNode = definingDeclNode->getChild(0);
   ASTBuilder builder(Context);
@@ -2677,8 +2681,9 @@ Type TypeResolver::resolveOpaqueReturnType(TypeRepr *repr,
 
   auto TypeArgs = ArrayRef<Type>(TypeArgsBuf);
   auto ty = builder.resolveOpaqueType(opaqueNode, TypeArgs, ordinal);
-  if (!ty) {
+  if (!ty || ty->hasError()) {
     diagnose(repr->getLoc(), diag::no_opaque_return_type_of);
+    return ErrorType::get(Context);
   }
   return ty;
 }

test/ModuleInterface/invalid-opaque-result-types.swift

@@ -0,0 +1,23 @@
+// Test that we emit a diagnostic (and don't crash) when we cannot resolve
+// an opaque result type reference.
+//
+// First, emit an empty module interface:
+//
+// RUN: %empty-directory(%t)
+// RUN: echo "" | %target-swift-frontend -typecheck -emit-module-interface-path %t/InvalidOpaqueResultType.swiftinterface -enable-library-evolution -swift-version 5 -module-name InvalidOpaqueResultType -
+//
+// Then, blit some invalid opaque result types into the interface
+//
+// Test that we reject broken type parameters
+// RUN: echo "public typealias SomeGenericBalderdash = @_opaqueReturnTypeOf(\"$somesuchnonsense\", 0) 🦸<InvalidParameter>" >> %t/InvalidOpaqueResultType.swiftinterface
+// Test that we reject types we cannot demangle
+// RUN: echo "public typealias SomesuchNonsense = @_opaqueReturnTypeOf(\"$somesuchnonsense\", 0) 🦸" >> %t/InvalidOpaqueResultType.swiftinterface
+//
+// The stage is set:
+//
+// RUN: not %target-swift-frontend -typecheck %s -I %t 2>&1 | %FileCheck %s
+
+// CHECK: cannot find type 'InvalidParameter' in scope
+// CHECK: unable to resolve type for _opaqueReturnTypeOf attribute
+// CHECK: failed to build module 'InvalidOpaqueResultType' from its module interface
+import InvalidOpaqueResultType