[Constraint solver] Add ConstraintKind::BindToPointerType.

This matches up with TypeMatchKind::BindToPointerType.

Author: DougGregor

lib/Sema/CSSimplify.cpp

@@ -1127,9 +1127,11 @@ ConstraintSystem::matchExistentialTypes(Type type1, Type type2,
 static ConstraintKind getConstraintKind(TypeMatchKind kind) {
   switch (kind) {
   case TypeMatchKind::BindType:
-  case TypeMatchKind::BindToPointerType:
     return ConstraintKind::Bind;
 
+  case TypeMatchKind::BindToPointerType:
+    return ConstraintKind::BindToPointerType;
+
   case TypeMatchKind::BindParamType:
     return ConstraintKind::BindParam;
 
@@ -3506,6 +3508,8 @@ static TypeMatchKind getTypeMatchKind(ConstraintKind kind) {
   case ConstraintKind::Bind: return TypeMatchKind::BindType;
   case ConstraintKind::Equal: return TypeMatchKind::SameType;
   case ConstraintKind::BindParam: return TypeMatchKind::BindParamType;
+  case ConstraintKind::BindToPointerType:
+    return TypeMatchKind::BindToPointerType;
   case ConstraintKind::Subtype: return TypeMatchKind::Subtype;
   case ConstraintKind::Conversion: return TypeMatchKind::Conversion;
   case ConstraintKind::ExplicitConversion:
@@ -4160,6 +4164,7 @@ ConstraintSystem::addConstraintImpl(ConstraintKind kind, Type first,
   case ConstraintKind::Equal:
   case ConstraintKind::Bind:
   case ConstraintKind::BindParam:
+  case ConstraintKind::BindToPointerType:
   case ConstraintKind::Subtype:
   case ConstraintKind::Conversion:
   case ConstraintKind::ExplicitConversion:
@@ -4230,6 +4235,7 @@ ConstraintSystem::simplifyConstraint(const Constraint &constraint) {
   case ConstraintKind::Bind:
   case ConstraintKind::Equal:
   case ConstraintKind::BindParam:
+  case ConstraintKind::BindToPointerType:
   case ConstraintKind::Subtype:
   case ConstraintKind::Conversion:
   case ConstraintKind::ExplicitConversion:

lib/Sema/CSSolver.cpp

@@ -676,6 +676,7 @@ static bool shouldBindToValueType(Constraint *constraint)
   case ConstraintKind::Bind:
   case ConstraintKind::Equal:
   case ConstraintKind::BindParam:
+  case ConstraintKind::BindToPointerType:
   case ConstraintKind::ConformsTo:
   case ConstraintKind::LiteralConformsTo:
   case ConstraintKind::CheckedCast:
@@ -757,6 +758,7 @@ static PotentialBindings getPotentialBindings(ConstraintSystem &cs,
     case ConstraintKind::Bind:
     case ConstraintKind::Equal:
     case ConstraintKind::BindParam:
+    case ConstraintKind::BindToPointerType:
     case ConstraintKind::Subtype:
     case ConstraintKind::Conversion:
     case ConstraintKind::ExplicitConversion:

lib/Sema/Constraint.cpp

@@ -53,6 +53,7 @@ Constraint::Constraint(ConstraintKind Kind, Type First, Type Second,
   case ConstraintKind::Bind:
   case ConstraintKind::Equal:
   case ConstraintKind::BindParam:
+  case ConstraintKind::BindToPointerType:
   case ConstraintKind::Subtype:
   case ConstraintKind::Conversion:
   case ConstraintKind::ExplicitConversion:
@@ -150,6 +151,7 @@ Constraint *Constraint::clone(ConstraintSystem &cs) const {
   case ConstraintKind::Bind:
   case ConstraintKind::Equal:
   case ConstraintKind::BindParam:
+  case ConstraintKind::BindToPointerType:
   case ConstraintKind::Subtype:
   case ConstraintKind::Conversion:
   case ConstraintKind::ExplicitConversion:
@@ -219,6 +221,7 @@ void Constraint::print(llvm::raw_ostream &Out, SourceManager *sm) const {
   case ConstraintKind::Bind: Out << " bind "; break;
   case ConstraintKind::Equal: Out << " equal "; break;
   case ConstraintKind::BindParam: Out << " bind param "; break;
+  case ConstraintKind::BindToPointerType: Out << " bind to pointer "; break;
   case ConstraintKind::Subtype: Out << " subtype "; break;
   case ConstraintKind::Conversion: Out << " conv "; break;
   case ConstraintKind::ExplicitConversion: Out << " expl conv "; break;
@@ -449,6 +452,7 @@ gatherReferencedTypeVars(Constraint *constraint,
   case ConstraintKind::ApplicableFunction:
   case ConstraintKind::Bind:
   case ConstraintKind::BindParam:
+  case ConstraintKind::BindToPointerType:
   case ConstraintKind::ArgumentConversion:
   case ConstraintKind::Conversion:
   case ConstraintKind::ExplicitConversion:

lib/Sema/Constraint.h

@@ -58,6 +58,8 @@ enum class ConstraintKind : char {
   /// type is an lvalue type with the same object type. Otherwise, the two
   /// types must be the same type.
   BindParam,
+  /// \brief Binds the first type to the element type of the second type.
+  BindToPointerType,
   /// \brief The first type is a subtype of the second type, i.e., a value
   /// of the type of the first type can be used wherever a value of the
   /// second type is expected.
@@ -464,6 +466,7 @@ class Constraint final : public llvm::ilist_node<Constraint>,
     case ConstraintKind::Bind:
     case ConstraintKind::Equal:
     case ConstraintKind::BindParam:
+    case ConstraintKind::BindToPointerType:
     case ConstraintKind::Subtype:
     case ConstraintKind::Conversion:
     case ConstraintKind::ExplicitConversion:

lib/Sema/ConstraintGraph.cpp

@@ -692,21 +692,22 @@ unsigned ConstraintGraph::computeConnectedComponents(
 /// edge in the graph.
 static bool shouldContractEdge(ConstraintKind kind) {
   switch (kind) {
-    case ConstraintKind::Bind:
-    case ConstraintKind::BindParam:
-    case ConstraintKind::Equal:
-    case ConstraintKind::BindOverload:
-
-    // We currently only allow subtype contractions for the purpose of 
-    // parameter binding constraints.
-    // TODO: We do this because of how inout parameter bindings are handled
-    // for implicit closure parameters. We should consider adjusting our
-    // current approach to unlock more opportunities for subtype contractions.
-    case ConstraintKind::Subtype:
-      return true;
-
-    default:
-      return false;
+  case ConstraintKind::Bind:
+  case ConstraintKind::BindParam:
+  case ConstraintKind::BindToPointerType:
+  case ConstraintKind::Equal:
+  case ConstraintKind::BindOverload:
+
+  // We currently only allow subtype contractions for the purpose of 
+  // parameter binding constraints.
+  // TODO: We do this because of how inout parameter bindings are handled
+  // for implicit closure parameters. We should consider adjusting our
+  // current approach to unlock more opportunities for subtype contractions.
+  case ConstraintKind::Subtype:
+    return true;
+
+  default:
+    return false;
   }
 }