Reject invalid derived Hashable members explicitly

Hashable doesn't quite have the know-how to reject invalid derivation contexts before hand.  Give it a little help by adding a way to retrieve if a decl added to the conformance context was invalid after type checking completes.  Otherwise we'll emit "Hashable is broken".

Author: CodaFi

lib/Sema/DerivedConformanceEquatableHashable.cpp

@@ -1251,7 +1251,11 @@ static ValueDecl *deriveHashable_hashValue(DerivedConformance &derived) {
       C, StaticSpellingKind::None, hashValuePat, /*InitExpr*/ nullptr,
       parentDC);
 
-  derived.addMembersToConformanceContext({hashValueDecl, patDecl});
+  // If any of the members we synthesized didn't typecheck, bail out.
+  if (derived.addMembersToConformanceContext({hashValueDecl, patDecl})) {
+    return nullptr;
+  }
+
   return hashValueDecl;
 }
 

lib/Sema/DerivedConformances.cpp

@@ -35,13 +35,16 @@ DeclContext *DerivedConformance::getConformanceContext() const {
   return cast<DeclContext>(ConformanceDecl);
 }
 
-void DerivedConformance::addMembersToConformanceContext(
+bool DerivedConformance::addMembersToConformanceContext(
     ArrayRef<Decl *> children) {
   auto IDC = cast<IterableDeclContext>(ConformanceDecl);
+  bool anyInvalid = false;
   for (auto child : children) {
     IDC->addMember(child);
     TypeChecker::typeCheckDecl(child);
+    anyInvalid |= child->isInvalid();
   }
+  return anyInvalid;
 }
 
 Type DerivedConformance::getProtocolType() const {

lib/Sema/DerivedConformances.h

@@ -46,7 +46,10 @@ class DerivedConformance {
   DeclContext *getConformanceContext() const;
 
   /// Add \c children as members of the context that declares the conformance.
-  void addMembersToConformanceContext(ArrayRef<Decl *> children);
+  ///
+  /// \returns True if any of the added members were found to be invalid after type
+  /// checking.
+  bool addMembersToConformanceContext(ArrayRef<Decl *> children);
 
   /// Get the declared type of the protocol that this is conformance is for.
   Type getProtocolType() const;

test/Sema/enum_conformance_synthesis.swift

@@ -61,7 +61,7 @@ func customHashable() {
 enum InvalidCustomHashable {
   case A, B
 
-  var hashValue: String { return "" } // expected-note{{previously declared here}}
+  var hashValue: String { return "" } // expected-note 2 {{previously declared here}}
 }
 func ==(x: InvalidCustomHashable, y: InvalidCustomHashable) -> String {
   return ""
@@ -72,7 +72,7 @@ func invalidCustomHashable() {
   s = InvalidCustomHashable.A.hashValue
   _ = s
   var _: Int = InvalidCustomHashable.A.hashValue
-  InvalidCustomHashable.A.hash(into: &hasher)
+  InvalidCustomHashable.A.hash(into: &hasher) // expected-error {{value of type 'InvalidCustomHashable' has no member 'hash'}}
 }
 
 // Check use of an enum's synthesized members before the enum is actually declared.