[ConstraintSystem] Improve type parameter requirement locators

lib/Sema/ConstraintLocator.cpp

@@ -77,6 +77,7 @@ void ConstraintLocator::Profile(llvm::FoldingSetNodeID &id, Expr *anchor,
     case OpenedGeneric:
     case KeyPathComponent:
     case ConditionalRequirement:
+    case TypeParameterRequirement:
       if (unsigned numValues = numNumericValuesInPathElement(elt.getKind())) {
         id.AddInteger(elt.getValue());
         if (numValues > 1)
@@ -243,6 +244,10 @@ void ConstraintLocator::dump(SourceManager *sm, raw_ostream &out) {
     case ConditionalRequirement:
       out << "conditional requirement #" << llvm::utostr(elt.getValue());
       break;
+
+    case TypeParameterRequirement:
+      out << "type parameter requirement #" << llvm::utostr(elt.getValue());
+      break;
     }
   }
 

lib/Sema/ConstraintLocator.h

@@ -125,6 +125,8 @@ class ConstraintLocator : public llvm::FoldingSetNode {
     KeyPathComponent,
     /// The Nth conditional requirement in the parent locator's conformance.
     ConditionalRequirement,
+    /// A single requirement placed on the type parameters.
+    TypeParameterRequirement,
   };
 
   /// \brief Determine the number of numeric values used for the given path
@@ -164,6 +166,7 @@ class ConstraintLocator : public llvm::FoldingSetNode {
     case TupleElement:
     case KeyPathComponent:
     case ConditionalRequirement:
+    case TypeParameterRequirement:
       return 1;
 
     case ApplyArgToParam:
@@ -217,6 +220,7 @@ class ConstraintLocator : public llvm::FoldingSetNode {
     case Witness:
     case KeyPathComponent:
     case ConditionalRequirement:
+    case TypeParameterRequirement:
       return 0;
 
     case FunctionArgument:
@@ -353,6 +357,10 @@ class ConstraintLocator : public llvm::FoldingSetNode {
       return PathElement(ConditionalRequirement, index);
     }
 
+    static PathElement getTypeRequirementComponent(unsigned index) {
+      return PathElement(TypeParameterRequirement, index);
+    }
+
     /// \brief Retrieve the kind of path element.
     PathElementKind getKind() const {
       switch (static_cast<StoredKind>(storedKind)) {

lib/Sema/ConstraintSystem.cpp

@@ -1051,7 +1051,10 @@ void ConstraintSystem::openGeneric(
   bindArchetypesFromContext(*this, outerDC, locatorPtr, replacements);
 
   // Add the requirements as constraints.
-  for (auto req : sig->getRequirements()) {
+  auto requirements = sig->getRequirements();
+  for (unsigned pos = 0, n = requirements.size(); pos != n; ++pos) {
+    const auto &req = requirements[pos];
+
     Optional<Requirement> openedReq;
     auto openedFirst = openType(req.getFirstType(), replacements);
 
@@ -1078,7 +1081,11 @@ void ConstraintSystem::openGeneric(
       openedReq = Requirement(kind, openedFirst, req.getLayoutConstraint());
       break;
     }
-    addConstraint(*openedReq, locatorPtr);
+
+    addConstraint(
+        *openedReq,
+        locator.withPathElement(ConstraintLocator::OpenedGeneric)
+            .withPathElement(LocatorPathElt::getTypeRequirementComponent(pos)));
   }
 }