[ConstraintSystem] Use specific locators when matching pack types.

Author: hborla

lib/Sema/CSSimplify.cpp

@@ -2423,14 +2423,17 @@ static PackType *replaceTypeVariablesWithFreshPacks(ConstraintSystem &cs,
       // wrapping a pack type variable. Otherwise, create a new scalar
       // type variable.
       //
-      // FIXME: Locator for diagnostics
       // FIXME: Other TVO_* flags for type variables?
+      auto elementLoc = cs.getConstraintLocator(loc,
+          LocatorPathElt::PackElement(freshTypeVars.size()));
       if (packExpansionElt != nullptr) {
-        auto *freshTypeVar = cs.createTypeVariable(loc, TVO_CanBindToPack);
+        auto *freshTypeVar =
+            cs.createTypeVariable(elementLoc, TVO_CanBindToPack);
         freshTypeVars.push_back(PackExpansionType::get(
             freshTypeVar, packExpansionElt->getCountType()));
       } else {
-        freshTypeVars.push_back(cs.createTypeVariable(loc, /*options=*/0));
+        freshTypeVars.push_back(
+            cs.createTypeVariable(elementLoc, /*options=*/0));
       }
     }
   }
@@ -2483,7 +2486,6 @@ static PackType *replaceTypeVariablesWithFreshPacks(ConstraintSystem &cs,
   // Bind each pack type variable occurring in the pattern type to its
   // binding pack that was constructed above.
   for (const auto &pair : typeVars) {
-    // FIXME: Locator for diagnostics
     cs.addConstraint(ConstraintKind::Bind,
                      pair.first, PackType::get(ctx, pair.second), locator);
   }
@@ -2521,7 +2523,6 @@ ConstraintSystem::matchPackExpansionTypes(PackExpansionType *expansion1,
     if (auto *pack2 = pattern2->getAs<PackType>()) {
       if (auto *pack1 = replaceTypeVariablesWithFreshPacks(
              *this, pattern1, pack2, locator)) {
-        // FIXME: Locator for diagnostics.
         addConstraint(kind, pack1, pack2, locator);
         return getTypeMatchSuccess();
       }
@@ -2537,7 +2538,6 @@ ConstraintSystem::matchPackExpansionTypes(PackExpansionType *expansion1,
     if (auto *pack1 = pattern1->getAs<PackType>()) {
       if (auto *pack2 = replaceTypeVariablesWithFreshPacks(
               *this, pattern2, pack1, locator)) {
-        // FIXME: Locator for diagnostics.
         addConstraint(kind, pack1, pack2, locator);
         return getTypeMatchSuccess();
       }
@@ -6849,8 +6849,6 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
                             kind, subflags, packLoc);
     }
     case TypeKind::PackExpansion: {
-      // FIXME: Need a new locator element
-
       auto expansion1 = cast<PackExpansionType>(desugar1);
       auto expansion2 = cast<PackExpansionType>(desugar2);
 

lib/Sema/ConstraintLocator.cpp

@@ -436,9 +436,11 @@ void LocatorPathElt::dump(raw_ostream &out) const {
     break;
   }
 
-  case ConstraintLocator::ConstraintLocator::PackType:
-    out << "pack type";
+  case ConstraintLocator::ConstraintLocator::PackType: {
+    auto packElt = elt.castTo<LocatorPathElt::PackType>();
+    out << "pack type '" << packElt.getType()->getString(PO) << "'";
     break;
+  }
 
   case ConstraintLocator::PackElement: {
     auto packElt = elt.castTo<LocatorPathElt::PackElement>();