Sema: Fix crash in IgnoreAssignmentDestinationType::diagnoseForAmbiguity()

Author: slavapestov

lib/Sema/CSFix.cpp

@@ -1796,15 +1796,18 @@ bool IgnoreAssignmentDestinationType::diagnoseForAmbiguity(
   if (!overload)
     return false;
 
-  auto memberName = overload->choice.getName().getBaseName();
+  auto declName = overload->choice.getName();
+  if (!declName)
+    return false;
+
   auto destType = solution.getType(assignment->getDest());
 
   auto &DE = cs.getASTContext().Diags;
   // TODO(diagnostics): It might be good to add a tailored diagnostic
   // for cases like this instead of using "contextual" one.
   DE.diagnose(assignment->getSrc()->getLoc(),
               diag::no_candidates_match_result_type,
-              memberName.userFacingName(),
+              declName.getBaseName().userFacingName(),
               solution.simplifyType(destType)->getRValueType());
 
   for (auto &entry : commonFixes) {

lib/Sema/ConstraintSystem.cpp

@@ -2037,7 +2037,7 @@ DeclName OverloadChoice::getName() const {
     case OverloadChoiceKind::MaterializePack:
     case OverloadChoiceKind::TupleIndex:
     case OverloadChoiceKind::ExtractFunctionIsolation:
-      llvm_unreachable("no name!");
+      return DeclName();
   }
 
   llvm_unreachable("Unhandled OverloadChoiceKind in switch.");

validation-test/compiler_crashers_2/d4a53522d2dce157.swift renamed to validation-test/compiler_crashers_2_fixed/d4a53522d2dce157.swift

@@ -1,3 +1,3 @@
 // {"kind":"typecheck","original":"e0be092d","signature":"swift::constraints::IgnoreAssignmentDestinationType::diagnoseForAmbiguity(llvm::ArrayRef<std::__1::pair<swift::constraints::Solution const*, swift::constraints::ConstraintFix const*>>) const"}
-// RUN: not --crash %target-swift-frontend -typecheck %s
+// RUN: not %target-swift-frontend -typecheck %s
 stride = (a:2).0