Merge pull request swiftlang#35729 from slavapestov/fix-generic-alias-property-wrapper-regression-5.4

Sema: Tweak assertion in CustomAttrTypeRequest to allow generic typealiases [5.4]

Author: slavapestov

lib/Sema/TypeCheckType.cpp

@@ -3970,12 +3970,26 @@ Type CustomAttrTypeRequest::evaluate(Evaluator &eval, CustomAttr *attr,
     };
   }
 
-  ASTContext &ctx = dc->getASTContext();
   const auto type = TypeResolution::forContextual(dc, options, unboundTyOpener)
                         .resolveType(attr->getTypeRepr());
 
-  // We always require the type to resolve to a nominal type.
-  if (!type->getAnyNominal()) {
+  // We always require the type to resolve to a nominal type. If the type was
+  // not a nominal type, we should have already diagnosed an error via
+  // CustomAttrNominalRequest.
+  auto checkType = [](Type type) -> bool {
+    while (auto *genericDecl = type->getAnyGeneric()) {
+      if (isa<NominalTypeDecl>(genericDecl))
+        return true;
+
+      auto *aliasDecl = cast<TypeAliasDecl>(genericDecl);
+      type = aliasDecl->getUnderlyingType();
+    }
+
+    return false;
+  };
+
+  if (!checkType(type)) {
+    ASTContext &ctx = dc->getASTContext();
     assert(ctx.Diags.hadAnyError());
     return ErrorType::get(ctx);
   }

test/decl/var/property_wrapper_generic_aliases.swift

@@ -0,0 +1,19 @@
+// RUN: %target-typecheck-verify-swift
+
+// https://bugs.swift.org/browse/SR-14143
+
+@propertyWrapper
+struct SomeLongFooName<Holder, T> {
+  var wrappedValue: T
+  
+  init(wrappedValue: T) {
+    self.wrappedValue = wrappedValue
+  }
+}
+
+
+struct Bar {
+  typealias Foo<T> = SomeLongFooName<Self, T>
+  
+  @Foo var baz: Bool = false
+}

test/decl/var/property_wrapper_generic_aliases_invalid.swift

@@ -0,0 +1,20 @@
+// RUN: %target-typecheck-verify-swift
+
+@propertyWrapper
+struct SomeStruct<T> {
+  var wrappedValue: T 
+    
+  init(wrappedValue: T) { 
+    self.wrappedValue = wrappedValue
+  } 
+}
+
+typealias Invalid1<T> = (T) -> ()
+typealias Invalid2<T> = SomeStruct<T>.Type
+typealias Invalid3 = SomeStruct<Bool>.Type
+
+struct Bar {
+  @Invalid1 var badWrapper1: Bool = false // expected-error {{unknown attribute 'Invalid1'}}
+  @Invalid2 var badWrapper2: Bool = false // expected-error {{unknown attribute 'Invalid2'}}
+  @Invalid3 var badWrapper3: Bool = false // expected-error {{unknown attribute 'Invalid3'}}
+}