[NFC] Rename @lvalue Locator Path Element

8271c1a removed the last hacky usage of ArrayElementType,
leaving behind just the @lvalue-to-inout conversions.  Rename
the locator path element to reflect this and do a bit of cleanup on the
unrelated-but-near-enough other hack RValueAdjustment.

lib/Sema/CSDiag.cpp

@@ -195,10 +195,11 @@ void constraints::simplifyLocator(Expr *&anchor,
       break;
 
     case ConstraintLocator::AutoclosureResult:
-    case ConstraintLocator::RvalueAdjustment:
+    case ConstraintLocator::LValueConversion:
+    case ConstraintLocator::RValueAdjustment:
     case ConstraintLocator::ScalarToTuple:
     case ConstraintLocator::UnresolvedMember:
-      // Arguments in autoclosure positions, rvalue adjustments, and
+      // Arguments in autoclosure positions, lvalue and rvalue adjustments, and
       // scalar-to-tuple conversions, and unresolved members are
       // implicit.
       path = path.slice(1);

lib/Sema/CSGen.cpp

@@ -1487,12 +1487,12 @@ namespace {
       // If there is an argument, apply it.
       if (auto arg = expr->getArgument()) {
         // The result type of the function must be convertible to the base type.
-        // TODO: we definitely want this to include ImplicitlyUnwrappedOptional; does it
+        // TODO: we definitely want this to include ImplicitlyUnwrappedOptional;
-        // need to include everything else in the world?
+        // does it need to include everything else in the world?
         auto outputTy = CS.createTypeVariable(
             CS.getConstraintLocator(expr, ConstraintLocator::FunctionResult));
         CS.addConstraint(ConstraintKind::Conversion, outputTy, baseTy,
-          CS.getConstraintLocator(expr, ConstraintLocator::RvalueAdjustment));
+          CS.getConstraintLocator(expr, ConstraintLocator::RValueAdjustment));
 
         // The function/enum case must be callable with the given argument.
         auto funcTy = FunctionType::get(CS.getType(arg), outputTy);
@@ -1505,7 +1505,7 @@ namespace {
 
       // Otherwise, the member needs to be convertible to the base type.
       CS.addConstraint(ConstraintKind::Conversion, memberTy, baseTy,
-        CS.getConstraintLocator(expr, ConstraintLocator::RvalueAdjustment));
+        CS.getConstraintLocator(expr, ConstraintLocator::RValueAdjustment));
       
       // The member type also needs to be convertible to the context type, which
       // preserves lvalue-ness.
@@ -2388,7 +2388,7 @@ namespace {
       auto tv = CS.createTypeVariable(CS.getConstraintLocator(expr));
       CS.addConstraint(ConstraintKind::DynamicTypeOf, tv,
                        CS.getType(expr->getBase()),
-           CS.getConstraintLocator(expr, ConstraintLocator::RvalueAdjustment));
+           CS.getConstraintLocator(expr, ConstraintLocator::RValueAdjustment));
       return tv;
     }
 

lib/Sema/CSSimplify.cpp

@@ -1925,7 +1925,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
                         cast<LValueType>(desugar2)->getObjectType(),
                         ConstraintKind::Equal, subflags,
                         locator.withPathElement(
-                          ConstraintLocator::ArrayElementType));
+                          ConstraintLocator::LValueConversion));
     
     case TypeKind::InOut:
       // If the RHS is an inout type, the LHS must be an @lvalue type.
@@ -1936,7 +1936,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
       return matchTypes(cast<InOutType>(desugar1)->getObjectType(),
                         cast<InOutType>(desugar2)->getObjectType(),
                         ConstraintKind::Equal, subflags,
-                  locator.withPathElement(ConstraintLocator::ArrayElementType));
+                  locator.withPathElement(ConstraintLocator::LValueConversion));
 
     case TypeKind::UnboundGeneric:
       llvm_unreachable("Unbound generic type should have been opened");
@@ -2303,7 +2303,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
       return matchTypes(type1, LValueType::get(iot->getObjectType()),
                         kind, subflags,
                         locator.withPathElement(
-                                ConstraintLocator::ArrayElementType));
+                                ConstraintLocator::LValueConversion));
     }
   }
 
@@ -2337,7 +2337,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
         return matchTypes(iot->getObjectType(), lvt->getObjectType(),
                           ConstraintKind::Bind, subflags,
                           locator.withPathElement(
-                            ConstraintLocator::ArrayElementType));
+                            ConstraintLocator::LValueConversion));
       }
     }
   }

lib/Sema/ConstraintLocator.cpp

@@ -61,13 +61,13 @@ void ConstraintLocator::Profile(llvm::FoldingSetNodeID &id, Expr *anchor,
     case SubscriptMember:
     case SubscriptResult:
     case ConstructorMember:
-    case RvalueAdjustment:
+    case LValueConversion:
+    case RValueAdjustment:
     case ClosureResult:
     case ParentType:
     case InstanceType:
     case SequenceIteratorProtocol:
     case GeneratorElementType:
-    case ArrayElementType:
     case ScalarToTuple:
     case AutoclosureResult:
     case GenericArgument:
@@ -115,10 +115,6 @@ void ConstraintLocator::dump(SourceManager *sm, raw_ostream &out) {
   for (auto elt : getPath()) {
     out << " -> ";
     switch (elt.getKind()) {
-    case ArrayElementType:
-      out << "array element";
-      break;
-
     case Archetype:
       out << "archetype '" << elt.getArchetype()->getString() << "'";
       break;
@@ -197,7 +193,11 @@ void ConstraintLocator::dump(SourceManager *sm, raw_ostream &out) {
       out << "parent type";
       break;
 
-    case RvalueAdjustment:
+    case LValueConversion:
+      out << "@lvalue-to-inout conversion";
+      break;
+
+    case RValueAdjustment:
       out << "rvalue adjustment";
       break;
 

lib/Sema/ConstraintLocator.h

@@ -95,8 +95,11 @@ public:
     SubscriptResult,
     /// \brief The lookup for a constructor member.
     ConstructorMember,
-    /// \brief Rvalue adjustment.
+    /// \brief An implicit @lvalue-to-inout conversion; only valid for operator
-    RvalueAdjustment,
+    /// arguments.
+    LValueConversion,
+    /// \brief RValue adjustment.
+    RValueAdjustment,
     /// \brief The result of a closure.
     ClosureResult,
     /// \brief The parent of a nested type.
@@ -107,8 +110,6 @@ public:
     SequenceIteratorProtocol,
     /// \brief The element type of a generator.
     GeneratorElementType,
-    /// \brief The element of an array type.
-    ArrayElementType,
     /// \brief The scalar type of a tuple type.
     ScalarToTuple,
     /// \brief An argument passed in an autoclosure parameter
@@ -152,13 +153,13 @@ public:
     case SubscriptMember:
     case SubscriptResult:
     case ConstructorMember:
-    case RvalueAdjustment:
+    case LValueConversion:
+    case RValueAdjustment:
     case ClosureResult:
     case ParentType:
     case InstanceType:
     case SequenceIteratorProtocol:
     case GeneratorElementType:
-    case ArrayElementType:
     case ScalarToTuple:
     case AutoclosureResult:
     case Requirement:
@@ -202,7 +203,6 @@ public:
     case ApplyArgToParam:
     case SequenceIteratorProtocol:
     case GeneratorElementType:
-    case ArrayElementType:
     case ClosureResult:
     case ConstructorMember:
     case InstanceType:
@@ -212,7 +212,8 @@ public:
     case MemberRefBase:
     case UnresolvedMember:
     case ParentType:
-    case RvalueAdjustment:
+    case LValueConversion:
+    case RValueAdjustment:
     case ScalarToTuple:
     case SubscriptIndex:
     case SubscriptMember:

lib/Sema/ConstraintSystem.cpp

@@ -1571,7 +1571,7 @@ resolveOverloadForDeclWithSpecialTypeCheckingSemantics(ConstraintSystem &CS,
     auto inputTuple = TupleType::get(inputArg, CS.getASTContext());
     
     CS.addConstraint(ConstraintKind::DynamicTypeOf, output, input,
-        CS.getConstraintLocator(locator, ConstraintLocator::RvalueAdjustment));
+        CS.getConstraintLocator(locator, ConstraintLocator::RValueAdjustment));
     refType = FunctionType::get(inputTuple, output);
     openedFullType = refType;
     return true;
@@ -1586,7 +1586,7 @@ resolveOverloadForDeclWithSpecialTypeCheckingSemantics(ConstraintSystem &CS,
         CS.getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
     CS.addConstraint(ConstraintKind::EscapableFunctionOf,
          escapeClosure, noescapeClosure,
-         CS.getConstraintLocator(locator, ConstraintLocator::RvalueAdjustment));
+         CS.getConstraintLocator(locator, ConstraintLocator::RValueAdjustment));
     auto result = CS.createTypeVariable(
         CS.getConstraintLocator(locator, ConstraintLocator::FunctionResult));
     auto bodyClosure = FunctionType::get(
@@ -1618,7 +1618,7 @@ resolveOverloadForDeclWithSpecialTypeCheckingSemantics(ConstraintSystem &CS,
         CS.getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
     CS.addConstraint(ConstraintKind::OpenedExistentialOf,
          openedTy, existentialTy,
-         CS.getConstraintLocator(locator, ConstraintLocator::RvalueAdjustment));
+         CS.getConstraintLocator(locator, ConstraintLocator::RValueAdjustment));
     auto result = CS.createTypeVariable(
         CS.getConstraintLocator(locator, ConstraintLocator::FunctionResult));
     auto bodyClosure = FunctionType::get(