[ConstraintSystem] Add a locator path element for the pattern of a pack expansion.

Author: hborla

include/swift/Sema/ConstraintLocatorPathElts.def

@@ -198,6 +198,9 @@ CUSTOM_LOCATOR_PATH_ELT(PackElement)
 /// The shape of a parameter pack.
 SIMPLE_LOCATOR_PATH_ELT(PackShape)
 
+/// The pattern  of a pack expansion.
+SIMPLE_LOCATOR_PATH_ELT(PackExpansionPattern)
+
 /// An unresolved member.
 SIMPLE_LOCATOR_PATH_ELT(UnresolvedMember)
 

lib/Sema/CSGen.cpp

@@ -2918,10 +2918,12 @@ namespace {
         CS.setType(binding, type);
       }
 
-      auto elementResultType = CS.getType(expr->getPatternExpr());
-      auto patternTy = CS.createTypeVariable(CS.getConstraintLocator(expr),
+      auto *patternLoc =
+          CS.getConstraintLocator(expr, ConstraintLocator::PackExpansionPattern);
+      auto patternTy = CS.createTypeVariable(patternLoc,
                                              TVO_CanBindToPack |
                                              TVO_CanBindToHole);
+      auto elementResultType = CS.getType(expr->getPatternExpr());
       CS.addConstraint(ConstraintKind::PackElementOf, elementResultType,
                        patternTy, CS.getConstraintLocator(expr));
 

lib/Sema/CSSimplify.cpp

@@ -7559,9 +7559,10 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifySubclassOfConstraint(
     for (unsigned i = 0, e = packType->getNumElements(); i < e; ++i) {
       auto eltType = packType->getElementType(i);
       if (auto *packExpansionType = eltType->getAs<PackExpansionType>()) {
-        // FIXME: Locator element for pack expansion pattern
+        auto patternLoc =
+            locator.withPathElement(ConstraintLocator::PackExpansionPattern);
         addConstraint(ConstraintKind::SubclassOf, packExpansionType->getPatternType(),
-                      classType, locator.withPathElement(LocatorPathElt::PackElement(i)));
+                      classType, patternLoc);
       } else {
         addConstraint(ConstraintKind::SubclassOf, eltType,
                       classType, locator.withPathElement(LocatorPathElt::PackElement(i)));
@@ -7677,11 +7678,12 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyConformsToConstraint(
     for (unsigned i = 0, e = packType->getNumElements(); i < e; ++i) {
       auto eltType = packType->getElementType(i);
       if (auto *packExpansionType = eltType->getAs<PackExpansionType>()) {
-        // FIXME: Locator element for pack expansion pattern
+        auto patternLoc =
+            locator.withPathElement(ConstraintLocator::PackExpansionPattern);
         addConstraint(ConstraintKind::ConformsTo,
                       packExpansionType->getPatternType(),
                       protocol->getDeclaredInterfaceType(),
-                      locator.withPathElement(LocatorPathElt::PackElement(i)));
+                      patternLoc);
       } else {
         addConstraint(ConstraintKind::ConformsTo, eltType,
                       protocol->getDeclaredInterfaceType(),

lib/Sema/ConstraintLocator.cpp

@@ -98,6 +98,7 @@ unsigned LocatorPathElt::getNewSummaryFlags() const {
   case ConstraintLocator::PackType:
   case ConstraintLocator::PackElement:
   case ConstraintLocator::PackShape:
+  case ConstraintLocator::PackExpansionPattern:
   case ConstraintLocator::PatternBindingElement:
   case ConstraintLocator::NamedPatternDecl:
   case ConstraintLocator::AnyPatternDecl:
@@ -450,6 +451,11 @@ void LocatorPathElt::dump(raw_ostream &out) const {
     break;
   }
 
+  case ConstraintLocator::PackExpansionPattern: {
+    out << "pack expansion pattern";
+    break;
+  }
+
   case ConstraintLocator::PatternBindingElement: {
     auto patternBindingElt =
         elt.castTo<LocatorPathElt::PatternBindingElement>();

lib/Sema/ConstraintSystem.cpp

@@ -5330,6 +5330,14 @@ void constraints::simplifyLocator(ASTNode &anchor,
     case ConstraintLocator::PackShape:
       break;
 
+    case ConstraintLocator::PackExpansionPattern: {
+      if (auto *expansion = getAsExpr<PackExpansionExpr>(anchor))
+        anchor = expansion->getPatternExpr();
+
+      path = path.slice(1);
+      break;
+    }
+
     case ConstraintLocator::PatternBindingElement: {
       auto pattern = path[0].castTo<LocatorPathElt::PatternBindingElement>();
       auto *patternBinding = cast<PatternBindingDecl>(anchor.get<Decl *>());