Merge pull request #19990 from xedin/rdar-45470505

[CSDiagnostics] Fix requirement source lookup to support initializers

Author: xedin

lib/Sema/CSDiagnostics.cpp

@@ -103,10 +103,16 @@ ValueDecl *RequirementFailure::getDeclRef() const {
     locator = cs.getConstraintLocator(
         ctor.withPathElement(PathEltKind::ApplyFunction)
             .withPathElement(PathEltKind::ConstructorMember));
-  } else if (isa<UnresolvedDotExpr>(anchor)) {
+  } else if (auto *UDE = dyn_cast<UnresolvedDotExpr>(anchor)) {
     ConstraintLocatorBuilder member(locator);
-    locator =
-        cs.getConstraintLocator(member.withPathElement(PathEltKind::Member));
+
+    if (UDE->getName().isSimpleName(DeclBaseName::createConstructor())) {
+      member = member.withPathElement(PathEltKind::ConstructorMember);
+    } else {
+      member = member.withPathElement(PathEltKind::Member);
+    }
+
+    locator = cs.getConstraintLocator(member);
   } else if (isa<SubscriptExpr>(anchor)) {
     ConstraintLocatorBuilder subscript(locator);
     locator = cs.getConstraintLocator(

lib/Sema/CSDiagnostics.h

@@ -163,6 +163,7 @@ class RequirementFailure : public FailureDiagnostic {
   RequirementFailure(Expr *expr, ConstraintSystem &cs,
                      ConstraintLocator *locator)
       : FailureDiagnostic(expr, cs, locator), AffectedDecl(getDeclRef()) {
+    assert(AffectedDecl);
     auto *anchor = getAnchor();
     expr->forEachChildExpr([&](Expr *subExpr) -> Expr * {
       auto *AE = dyn_cast<ApplyExpr>(subExpr);

validation-test/Sema/type_checker_crashers_fixed/rdar45470505.swift

@@ -0,0 +1,16 @@
+// RUN: %target-typecheck-verify-swift
+
+extension BinaryInteger {
+  init(bytes: [UInt8]) { fatalError() }
+
+  init<S: Sequence>(bytes: S) where S.Iterator.Element == UInt8 {
+    self.init(bytes // expected-error {{ambiguous reference to initializer 'init(_:)'}}
+// expected-note@-1 {{}}
+
+extension
+// expected-error@-1 {{declaration is only valid at file scope}}
+// expected-error@-2 {{expected ')' in expression list}}
+// expected-error@-3 {{expected '{' in extension}}
+  }
+// expected-error@-1 {{expected type name in extension declaration}}
+}