[Constraint] Add an ability to attach a fix to BindOverload constraint

Author: xedin

lib/Sema/Constraint.cpp

@@ -166,9 +166,9 @@ Constraint::Constraint(ConstraintKind kind, Type first, Type second,
 }
 
 Constraint::Constraint(Type type, OverloadChoice choice, DeclContext *useDC,
-                       ConstraintLocator *locator,
+                       ConstraintFix *fix, ConstraintLocator *locator,
                        ArrayRef<TypeVariableType *> typeVars)
-    : Kind(ConstraintKind::BindOverload), HasRestriction(false),
+    : Kind(ConstraintKind::BindOverload), TheFix(fix), HasRestriction(false),
       IsActive(false), IsDisabled(false), RememberChoice(false),
       IsFavored(false),
       NumTypeVariables(typeVars.size()), Overload{type, choice, useDC},
@@ -639,18 +639,7 @@ Constraint *Constraint::createBindOverload(ConstraintSystem &cs, Type type,
                                            OverloadChoice choice, 
                                            DeclContext *useDC,
                                            ConstraintLocator *locator) {
-  // Collect type variables.
-  SmallVector<TypeVariableType *, 4> typeVars;
-  if (type->hasTypeVariable())
-    type->getTypeVariables(typeVars);
-  if (auto baseType = choice.getBaseType()) {
-    baseType->getTypeVariables(typeVars);
-  }
-
-  // Create the constraint.
-  unsigned size = totalSizeToAlloc<TypeVariableType*>(typeVars.size());
-  void *mem = cs.getAllocator().Allocate(size, alignof(Constraint));
-  return new (mem) Constraint(type, choice, useDC, locator, typeVars);
+  return createFixedChoice(cs, type, choice, useDC, /*fix=*/nullptr, locator);
 }
 
 Constraint *Constraint::createRestricted(ConstraintSystem &cs, 
@@ -690,6 +679,25 @@ Constraint *Constraint::createFixed(ConstraintSystem &cs, ConstraintKind kind,
   return new (mem) Constraint(kind, fix, first, second, locator, typeVars);
 }
 
+Constraint *Constraint::createFixedChoice(ConstraintSystem &cs, Type type,
+                                          OverloadChoice choice,
+                                          DeclContext *useDC,
+                                          ConstraintFix *fix,
+                                          ConstraintLocator *locator) {
+  // Collect type variables.
+  SmallVector<TypeVariableType *, 4> typeVars;
+  if (type->hasTypeVariable())
+    type->getTypeVariables(typeVars);
+  if (auto baseType = choice.getBaseType()) {
+    baseType->getTypeVariables(typeVars);
+  }
+
+  // Create the constraint.
+  unsigned size = totalSizeToAlloc<TypeVariableType *>(typeVars.size());
+  void *mem = cs.getAllocator().Allocate(size, alignof(Constraint));
+  return new (mem) Constraint(type, choice, useDC, fix, locator, typeVars);
+}
+
 Constraint *Constraint::createDisjunction(ConstraintSystem &cs,
                                           ArrayRef<Constraint *> constraints,
                                           ConstraintLocator *locator,

lib/Sema/Constraint.h

@@ -339,9 +339,10 @@ class Constraint final : public llvm::ilist_node<Constraint>,
              ConstraintLocator *locator,
              ArrayRef<TypeVariableType *> typeVars);
 
-  /// Construct a new overload-binding constraint.
+  /// Construct a new overload-binding constraint, which might have a fix.
   Constraint(Type type, OverloadChoice choice, DeclContext *useDC,
-             ConstraintLocator *locator, ArrayRef<TypeVariableType *> typeVars);
+             ConstraintFix *fix, ConstraintLocator *locator,
+             ArrayRef<TypeVariableType *> typeVars);
 
   /// Construct a restricted constraint.
   Constraint(ConstraintKind kind, ConversionRestrictionKind restriction,
@@ -399,6 +400,12 @@ class Constraint final : public llvm::ilist_node<Constraint>,
                                  ConstraintFix *fix, Type first, Type second,
                                  ConstraintLocator *locator);
 
+  /// Create a bind overload choice with a fix.
+  static Constraint *createFixedChoice(ConstraintSystem &cs, Type type,
+                                       OverloadChoice choice,
+                                       DeclContext *useDC, ConstraintFix *fix,
+                                       ConstraintLocator *locator);
+
   /// Create a new disjunction constraint.
   static Constraint *createDisjunction(ConstraintSystem &cs,
                                        ArrayRef<Constraint *> constraints,