[CSFix] NFC: Add a common base class for all requirement failures

(cherry picked from commit edb6ef0)

Author: xedin

include/swift/Sema/CSFix.h

@@ -587,21 +587,36 @@ class RelabelArguments final
   }
 };
 
+class RequirementFix : public ConstraintFix {
+protected:
+  Type LHS;
+  Type RHS;
+
+  RequirementFix(ConstraintSystem &cs, FixKind kind, Type lhs, Type rhs,
+                 ConstraintLocator *locator)
+      : ConstraintFix(cs, kind, locator), LHS(lhs), RHS(rhs) {}
+
+public:
+  std::string getName() const override = 0;
+
+  Type lhsType() const { return LHS; }
+  Type rhsType() const { return RHS; }
+
+  bool diagnose(const Solution &solution,
+                bool asNote = false) const override = 0;
+};
+
 /// Add a new conformance to the type to satisfy a requirement.
-class MissingConformance final : public ConstraintFix {
+class MissingConformance final : public RequirementFix {
   // Determines whether given protocol type comes from the context e.g.
   // assignment destination or argument comparison.
   bool IsContextual;
 
-  Type NonConformingType;
-  // This could either be a protocol or protocol composition.
-  Type ProtocolType;
-
   MissingConformance(ConstraintSystem &cs, bool isContextual, Type type,
                      Type protocolType, ConstraintLocator *locator)
-      : ConstraintFix(cs, FixKind::AddConformance, locator),
-        IsContextual(isContextual), NonConformingType(type),
-        ProtocolType(protocolType) {}
+      : RequirementFix(cs, FixKind::AddConformance, type, protocolType,
+                       locator),
+        IsContextual(isContextual) {}
 
 public:
   std::string getName() const override {
@@ -620,9 +635,9 @@ class MissingConformance final : public ConstraintFix {
                                            Type protocolType,
                                            ConstraintLocator *locator);
 
-  Type getNonConformingType() { return NonConformingType; }
+  Type getNonConformingType() const { return LHS; }
 
-  Type getProtocolType() { return ProtocolType; }
+  Type getProtocolType() const { return RHS; }
 
   bool isEqual(const ConstraintFix *other) const;
 
@@ -633,13 +648,11 @@ class MissingConformance final : public ConstraintFix {
 
 /// Skip same-type generic requirement constraint,
 /// and assume that types are equal.
-class SkipSameTypeRequirement final : public ConstraintFix {
-  Type LHS, RHS;
-
+class SkipSameTypeRequirement final : public RequirementFix {
   SkipSameTypeRequirement(ConstraintSystem &cs, Type lhs, Type rhs,
                           ConstraintLocator *locator)
-      : ConstraintFix(cs, FixKind::SkipSameTypeRequirement, locator), LHS(lhs),
-        RHS(rhs) {}
+      : RequirementFix(cs, FixKind::SkipSameTypeRequirement, lhs, rhs,
+                       locator) {}
 
 public:
   std::string getName() const override {
@@ -648,9 +661,6 @@ class SkipSameTypeRequirement final : public ConstraintFix {
 
   bool diagnose(const Solution &solution, bool asNote = false) const override;
 
-  Type lhsType() { return LHS; }
-  Type rhsType() { return RHS; }
-
   static SkipSameTypeRequirement *create(ConstraintSystem &cs, Type lhs,
                                          Type rhs, ConstraintLocator *locator);
 
@@ -661,13 +671,11 @@ class SkipSameTypeRequirement final : public ConstraintFix {
 
 /// Skip same-shape generic requirement constraint,
 /// and assume that types are equal.
-class SkipSameShapeRequirement final : public ConstraintFix {
-  Type LHS, RHS;
-
+class SkipSameShapeRequirement final : public RequirementFix {
   SkipSameShapeRequirement(ConstraintSystem &cs, Type lhs, Type rhs,
                            ConstraintLocator *locator)
-      : ConstraintFix(cs, FixKind::SkipSameShapeRequirement, locator), LHS(lhs),
-        RHS(rhs) {}
+      : RequirementFix(cs, FixKind::SkipSameShapeRequirement, lhs, rhs,
+                       locator) {}
 
 public:
   std::string getName() const override {
@@ -676,9 +684,6 @@ class SkipSameShapeRequirement final : public ConstraintFix {
 
   bool diagnose(const Solution &solution, bool asNote = false) const override;
 
-  Type lhsType() { return LHS; }
-  Type rhsType() { return RHS; }
-
   static SkipSameShapeRequirement *create(ConstraintSystem &cs, Type lhs,
                                           Type rhs, ConstraintLocator *locator);
 
@@ -689,13 +694,11 @@ class SkipSameShapeRequirement final : public ConstraintFix {
 
 /// Skip 'superclass' generic requirement constraint,
 /// and assume that types are equal.
-class SkipSuperclassRequirement final : public ConstraintFix {
-  Type LHS, RHS;
-
+class SkipSuperclassRequirement final : public RequirementFix {
   SkipSuperclassRequirement(ConstraintSystem &cs, Type lhs, Type rhs,
                             ConstraintLocator *locator)
-      : ConstraintFix(cs, FixKind::SkipSuperclassRequirement, locator),
-        LHS(lhs), RHS(rhs) {}
+      : RequirementFix(cs, FixKind::SkipSuperclassRequirement, lhs, rhs,
+                       locator) {}
 
 public:
   std::string getName() const override {

lib/Sema/CSFix.cpp

@@ -400,12 +400,13 @@ bool MissingConformance::diagnose(const Solution &solution, bool asNote) const {
     auto &cs = solution.getConstraintSystem();
     auto context = cs.getContextualTypePurpose(locator->getAnchor());
     MissingContextualConformanceFailure failure(
-        solution, context, NonConformingType, ProtocolType, locator);
+        solution, context, getNonConformingType(), getProtocolType(), locator);
     return failure.diagnose(asNote);
   }
 
   MissingConformanceFailure failure(
-      solution, locator, std::make_pair(NonConformingType, ProtocolType));
+      solution, locator,
+      std::make_pair(getNonConformingType(), getProtocolType()));
   return failure.diagnose(asNote);
 }
 
@@ -433,8 +434,9 @@ bool MissingConformance::isEqual(const ConstraintFix *other) const {
     return false;
 
   return IsContextual == conformanceFix->IsContextual &&
-         NonConformingType->isEqual(conformanceFix->NonConformingType) &&
-         ProtocolType->isEqual(conformanceFix->ProtocolType);
+         getNonConformingType()->isEqual(
+             conformanceFix->getNonConformingType()) &&
+         getProtocolType()->isEqual(conformanceFix->getProtocolType());
 }
 
 MissingConformance *