Sema: Use TypeResolution::forInterface() to resolve type alias underlying types

Author: slavapestov

lib/Sema/TypeCheckDecl.cpp

@@ -2057,7 +2057,7 @@ static NominalTypeDecl *resolveSingleNominalTypeDecl(
 
   TypeResolutionOptions options = TypeResolverContext::TypeAliasDecl;
   options |= flags;
-  if (tc.validateType(typeLoc, TypeResolution::forContextual(DC), options))
+  if (tc.validateType(typeLoc, TypeResolution::forInterface(DC), options))
     return nullptr;
 
   return typeLoc.getType()->getAnyNominal();
@@ -3469,7 +3469,7 @@ static void validateTypealiasType(TypeChecker &tc, TypeAliasDecl *typeAlias) {
   }
 
   if (tc.validateType(typeAlias->getUnderlyingTypeLoc(),
-                      TypeResolution::forContextual(typeAlias), options)) {
+                      TypeResolution::forInterface(typeAlias), options)) {
     typeAlias->setInvalid();
     typeAlias->getUnderlyingTypeLoc().setInvalidType(tc.Context);
   }

test/decl/typealias/protocol.swift

@@ -144,13 +144,18 @@ protocol P3 {
 
 // Test for not crashing on recursive aliases
 protocol Circular {
-  typealias Y = Self.Y // expected-error {{type alias 'Y' is not a member type of 'Self'}}
+  typealias Y = Self.Y // expected-error {{'Y' is not a member type of 'Self'}}
+  // expected-note@-1 {{did you mean 'Y'?}}
 
   typealias Y2 = Y2 // expected-error {{type alias 'Y2' references itself}}
   // expected-note@-1 {{type declared here}}
+  // expected-note@-2 {{did you mean 'Y2'?}}
 
   typealias Y3 = Y4 // expected-note {{type declared here}}
+  // expected-note@-1 {{did you mean 'Y3'?}}
+
   typealias Y4 = Y3 // expected-error {{type alias 'Y3' references itself}}
+  // expected-note@-1 {{did you mean 'Y4'?}}
 }
 
 // Qualified and unqualified references to protocol typealiases from concrete type