Merge pull request #67798 from slavapestov/fix-rdar113103854

Sema: Fix a couple of problems in checkContextualRequirements()

Author: slavapestov

lib/Sema/TypeCheckType.cpp

@@ -603,29 +603,43 @@ bool TypeChecker::checkContextualRequirements(GenericTypeDecl *decl,
     return true;
   }
 
+  // Protocols can't appear in constrained extensions, and their where
+  // clauses pertain to the requirement signature of the protocol and not
+  // its generic signature.
+  if (isa<ProtocolDecl>(decl))
+    return true;
+
+  auto *dc = decl->getDeclContext();
+
+  const auto genericSig = decl->getGenericSignature();
+
+  if (genericSig.getPointer() ==
+      dc->getSelfNominalTypeDecl()->getGenericSignature().getPointer()) {
+    return true;
+  }
+
+  // Otherwise, our decl has a where clause of its own, or its inside of a
+  // constrained extension.
   SourceLoc noteLoc;
   {
-    // We are interested in either a contextual where clause or
-    // a constrained extension context.
-    const auto ext = dyn_cast<ExtensionDecl>(decl->getDeclContext());
-    if (decl->getTrailingWhereClause())
-      noteLoc = decl->getLoc();
-    else if (ext && ext->isConstrainedExtension())
+    const auto ext = dyn_cast<ExtensionDecl>(dc);
+    if (ext && genericSig.getPointer() ==
+        ext->getGenericSignature().getPointer()) {
       noteLoc = ext->getLoc();
-    else
-      return true;
+    } else {
+      noteLoc = decl->getLoc();
+    }
 
     if (noteLoc.isInvalid())
       noteLoc = loc;
   }
 
-  const auto subMap = parentTy->getContextSubstitutions(decl->getDeclContext());
-  const auto genericSig = decl->getGenericSignature();
-
+  const auto subMap = parentTy->getContextSubstitutions(dc);
   const auto substitutions = [&](SubstitutableType *type) -> Type {
     auto result = QueryTypeSubstitutionMap{subMap}(type);
     if (result->hasTypeParameter()) {
       if (contextSig) {
+        // Avoid building this generic environment unless we need it.
         auto *genericEnv = contextSig.getGenericEnvironment();
         return genericEnv->mapTypeIntoContext(result);
       }

test/Sema/Inputs/where_clause_across_module_boundaries_module.swift

@@ -23,3 +23,11 @@ public extension DefaultsSerializable where Self: RawRepresentable {
 
 public struct ModuleAFoo: Codable, DefaultsSerializable {
 }
+
+public struct AliasTest<T> {
+  public typealias A = T.Element where T: Collection
+}
+
+extension AliasTest where T: Collection {
+  public typealias B = T.Element
+}

test/Sema/where_clause_across_module_boundaries.swift

@@ -14,3 +14,10 @@ struct ModuleBFoo: Codable, DefaultsSerializable {
 enum ModuleBBar: Int, Codable, DefaultsSerializable { // expected-error {{type 'ModuleBBar' does not conform to protocol 'DefaultsSerializable'}}
   case foo, bar
 }
+
+func foo() {
+  _ = AliasTest<Int>.A.self // expected-error {{type 'Int' does not conform to protocol 'Collection'}}
+  _ = AliasTest<Int>.B.self // expected-error {{type 'Int' does not conform to protocol 'Collection'}}
+  _ = AliasTest<String>.A.self
+  _ = AliasTest<String>.B.self
+}

test/decl/nested/protocol.swift

@@ -114,3 +114,16 @@ func testLookup<T: OuterForUFI.Inner>(_ x: T) {
   x.req()
   x.extMethod()
 }
+
+// rdar://problem/113103854
+
+protocol Q {
+  associatedtype A
+}
+
+struct OuterNonGeneric {
+  protocol P: Q where Self.A == Int {}
+  // expected-error@-1 {{protocol 'P' cannot be nested inside another declaration}}
+}
+
+func usesProtoWithWhereClause<T: OuterNonGeneric.P>(_: T) {}

validation-test/compiler_crashers_2_fixed/0161-issue-49119.swift

@@ -8,8 +8,8 @@ protocol P {
 
 struct Type<Param> {}
 extension Type: P where Param: P, Param.A == Type<Param> {
-  // expected-error@-1 5{{extension of generic struct 'Type' has self-referential generic requirements}}
-  // expected-note@-2 5{{through reference here}}
+  // expected-error@-1 6{{extension of generic struct 'Type' has self-referential generic requirements}}
+  // expected-note@-2 6{{through reference here}}
   // expected-error@-3 {{type 'Type<Param>' does not conform to protocol 'P'}}
   typealias A = Param
   // expected-note@-1 2{{through reference here}}