[ConstraintSystem] Improve type parameter requirement locators

When opening generic types with type parameter requirements,
add information about requirement location to the locator of each
generated constraint to make it easier to extract such information
if needed.

Author: xedin

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)));
   }
 }