[ConstraintSystem] Find solutions for code that contains circular member

references in the new diagnostic infrastructure.

Author: hborla

lib/Sema/CSSimplify.cpp

@@ -5461,22 +5461,9 @@ performMemberLookup(ConstraintKind constraintKind, DeclNameRef memberName,
   auto addChoice = [&](OverloadChoice candidate) {
     auto decl = candidate.getDecl();
 
-    // In a pattern binding initializer, immediately reject all of its bound
-    // variables. These would otherwise allow circular references.
-    if (auto *PBI = dyn_cast<PatternBindingInitializer>(DC)) {
-      if (auto *VD = dyn_cast<VarDecl>(decl)) {
-        if (PBI->getBinding() == VD->getParentPatternBinding()) {
-          // If this is a recursive reference to an instance variable,
-          // try to see if we can give a good diagnostic by adding it as
-          // an unviable candidate.
-          if (!VD->isStatic()) {
-            result.addUnviable(candidate,
-                               MemberLookupResult::UR_InstanceMemberOnType);
-          }
-          return;
-        }
-      }
-    }
+    // Reject circular references immediately.
+    if (decl->isRecursiveValidation())
+      return;
 
     // If the result is invalid, skip it.
     if (decl->isInvalid()) {

test/NameBinding/name_lookup.swift

@@ -619,20 +619,18 @@ struct PatternBindingWithTwoVars2 { var x = y, y = 3 }
 // expected-error@-1 {{cannot use instance member 'y' within property initializer; property initializers run before 'self' is available}}
 
 struct PatternBindingWithTwoVars3 { var x = y, y = x }
-// expected-error@-1 {{cannot use instance member 'x' within property initializer; property initializers run before 'self' is available}}
-// expected-error@-2 {{cannot use instance member 'y' within property initializer; property initializers run before 'self' is available}}
-// expected-error@-3 {{circular reference}}
+// expected-error@-1 {{circular reference}}
+// expected-note@-2 {{through reference here}}
+// expected-note@-3 {{through reference here}}
 // expected-note@-4 {{through reference here}}
 // expected-note@-5 {{through reference here}}
 // expected-note@-6 {{through reference here}}
-// expected-note@-7 {{through reference here}}
+// expected-error@-7 {{circular reference}}
 // expected-note@-8 {{through reference here}}
-// expected-error@-9 {{circular reference}}
+// expected-note@-9 {{through reference here}}
 // expected-note@-10 {{through reference here}}
 // expected-note@-11 {{through reference here}}
 // expected-note@-12 {{through reference here}}
-// expected-note@-13 {{through reference here}}
-// expected-note@-14 {{through reference here}}
 
 // https://bugs.swift.org/browse/SR-9015
 func sr9015() {

test/decl/overload.swift

@@ -577,23 +577,27 @@ enum SR_10084_E_8 {
 }
 
 enum SR_10084_E_9 {
-  case A // expected-note {{'A' previously declared here}}
+  case A // expected-note {{'A' previously declared here}} expected-note {{found this candidate}}
   static let A: SR_10084_E_9 = .A // expected-error {{invalid redeclaration of 'A'}}
+  // expected-error@-1 {{ambiguous use of 'A'}} expected-note@-1 {{found this candidate}}
 }
 
 enum SR_10084_E_10 {
   static let A: SR_10084_E_10 = .A // expected-note {{'A' previously declared here}}
-  case A // expected-error {{invalid redeclaration of 'A'}}
+  // expected-error@-1 {{ambiguous use of 'A'}} expected-note@-1 {{found this candidate}}
+  case A // expected-error {{invalid redeclaration of 'A'}} expected-note {{found this candidate}}
 }
 
 enum SR_10084_E_11 {
-  case A // expected-note {{'A' previously declared here}}
+  case A // expected-note {{'A' previously declared here}} expected-note {{found this candidate}}
   static var A: SR_10084_E_11 = .A // expected-error {{invalid redeclaration of 'A'}}
+  // expected-error@-1 {{ambiguous use of 'A'}} expected-note@-1 {{found this candidate}}
 }
 
 enum SR_10084_E_12 {
   static var A: SR_10084_E_12 = .A // expected-note {{'A' previously declared here}}
-  case A // expected-error {{invalid redeclaration of 'A'}}
+  // expected-error@-1 {{ambiguous use of 'A'}} expected-note@-1 {{found this candidate}}
+  case A // expected-error {{invalid redeclaration of 'A'}} expected-note {{found this candidate}}
 }
 
 enum SR_10084_E_13 {