[Type checker] Produce diagnostics for each of the evaluator requests.

We were suppressing diagnostics for some request kinds; we shouldn't
do that.

Author: DougGregor

include/swift/Sema/TypeCheckRequests.h

@@ -58,8 +58,8 @@ class InheritedTypeRequest :
 public:
   // Cycle handling
   Type breakCycle() const { return Type(); }
-  void diagnoseCycle(DiagnosticEngine &diags) const { }
-  void noteCycleStep(DiagnosticEngine &diags) const { }
+  void diagnoseCycle(DiagnosticEngine &diags) const;
+  void noteCycleStep(DiagnosticEngine &diags) const;
 
   // Caching
   bool isCached() const { return true; }

lib/Sema/TypeCheckRequests.cpp

@@ -117,6 +117,18 @@ Type InheritedTypeRequest::operator()(
   return inheritedType ? inheritedType : ErrorType::get(tc.Context);
 }
 
+void InheritedTypeRequest::diagnoseCycle(DiagnosticEngine &diags) const {
+  const auto &storage = getStorage();
+  auto &typeLoc = getTypeLoc(std::get<0>(storage), std::get<1>(storage));
+  diags.diagnose(typeLoc.getLoc(), diag::circular_reference);
+}
+
+void InheritedTypeRequest::noteCycleStep(DiagnosticEngine &diags) const {
+  const auto &storage = getStorage();
+  auto &typeLoc = getTypeLoc(std::get<0>(storage), std::get<1>(storage));
+  diags.diagnose(typeLoc.getLoc(), diag::circular_reference_through);
+}
+
 Optional<Type> InheritedTypeRequest::getCachedResult() const {
   const auto &storage = getStorage();
   auto &typeLoc = getTypeLoc(std::get<0>(storage), std::get<1>(storage));
@@ -218,15 +230,15 @@ Type EnumRawTypeRequest::operator()(Evaluator &evaluator,
 
 void EnumRawTypeRequest::diagnoseCycle(DiagnosticEngine &diags) const {
   // FIXME: Improve this diagnostic.
-  auto classDecl = std::get<0>(getStorage());
-  std::string className = "'" + std::string(classDecl->getNameStr()) + "'";
-  diags.diagnose(classDecl, diag::circular_class_inheritance, className);
+  auto enumDecl = std::get<0>(getStorage());
+  std::string className = "'" + std::string(enumDecl->getNameStr()) + "'";
+  diags.diagnose(enumDecl, diag::circular_enum_inheritance, className);
 }
 
 void EnumRawTypeRequest::noteCycleStep(DiagnosticEngine &diags) const {
-  auto classDecl = std::get<0>(getStorage());
+  auto enumDecl = std::get<0>(getStorage());
   // FIXME: Customize this further.
-  diags.diagnose(classDecl, diag::circular_reference_through);
+  diags.diagnose(enumDecl, diag::circular_reference_through);
 }
 
 Optional<Type> EnumRawTypeRequest::getCachedResult() const {

test/decl/class/circular_inheritance.swift

@@ -14,22 +14,27 @@ class Automorphism : Automorphism { } // expected-error{{circular class inherita
 let _ = A() // expected-error{{'A' cannot be constructed because it has no accessible initializers}}
 
 // FIXME: Not technically a circular dependency.
-class Left : Right.Hand { // expected-error{{circular class inheritance 'Left'}}
+class Left  // expected-error{{circular class inheritance 'Left'}}
+    : Right.Hand { // expected-note{{through reference here}}
   class Hand {}
 }
 
-class Right : Left.Hand { // expected-note{{through reference here}}
+class Right // expected-note{{through reference here}}
+  : Left.Hand { // expected-note{{through reference here}}
   class Hand {}
 }
 
 class Outer {
   class Inner : Outer {}
 }
 
-class Outer2 : Outer2.Inner { // expected-error{{circular class inheritance 'Outer2'}}
+class Outer2 // expected-error{{circular class inheritance 'Outer2'}}
+    : Outer2.Inner { // expected-note{{through reference here}}
+
   class Inner {}
 }
 
-class Outer3 : Outer3.Inner<Int> { // expected-error{{circular class inheritance 'Outer3'}}
+class Outer3 // expected-error{{circular class inheritance 'Outer3'}}
+    : Outer3.Inner<Int> { // expected-note{{through reference here}}
   class Inner<T> {}
 }