[Diagnostics] Fix requirement note to properly handle layout requirements

Layout requirement doesn't have a second type since it's always `AnyObject`,
requirement failure note should handle that, otherwise in no assertion builds
this would crash in diagnostic engine trying to emit the note.

Resolves: rdar://79672230

Author: xedin

lib/Sema/CSDiagnostics.cpp

@@ -399,8 +399,14 @@ bool RequirementFailure::diagnoseAsNote() {
   const auto &req = getRequirement();
   const auto *reqDC = getRequirementDC();
 
+  // Layout requirement doesn't have a second type, let's always
+  // `AnyObject`.
+  auto requirementTy = req.getKind() == RequirementKind::Layout
+                           ? getASTContext().getAnyObjectType()
+                           : req.getSecondType();
+
   emitDiagnosticAt(reqDC->getAsDecl(), getDiagnosticAsNote(), getLHS(),
-                   getRHS(), req.getFirstType(), req.getSecondType());
+                   getRHS(), req.getFirstType(), requirementTy);
   return true;
 }
 

test/Constraints/overload.swift

@@ -246,3 +246,14 @@ func test_no_hole_propagation() {
     return arguments.reduce(0, +) // expected-error {{cannot convert value of type 'Int' to expected argument type 'String'}}
   }
 }
+
+// rdar://79672230 - crash due to unsatisfied `: AnyObject` requirement
+func rdar79672230() {
+  struct MyType {}
+
+  func test(_ representation: MyType) -> Bool {} // expected-note {{found candidate with type 'MyType'}}
+  func test<T>(_ object: inout T) -> Bool where T : AnyObject {} // expected-note {{candidate requires that 'MyType' conform to 'AnyObject' (requirement specified as 'T' : 'AnyObject')}}
+
+  var t: MyType = MyType()
+  test(&t) // expected-error {{no exact matches in call to local function 'test'}}
+}