[Diagnostics] Use ContextualFailure and ContextualMistatch as base classes

for `AutoClosurePointerConversionFailure` and `AllowAutoClosurePointerConversion`
respectively.

Author: hborla

lib/Sema/CSDiagnostics.cpp

@@ -1981,7 +1981,7 @@ bool AutoClosureForwardingFailure::diagnoseAsError() {
 bool AutoClosurePointerConversionFailure::diagnoseAsError() {
   auto *anchor = getAnchor();
   auto diagnostic = diag::invalid_autoclosure_pointer_conversion;
-  emitDiagnostic(anchor->getLoc(), diagnostic, PointeeType, PointerType)
+  emitDiagnostic(anchor->getLoc(), diagnostic, getFromType(), getToType())
       .highlight(anchor->getSourceRange());
   return true;
 }

lib/Sema/CSDiagnostics.h

@@ -785,16 +785,12 @@ class AutoClosureForwardingFailure final : public FailureDiagnostic {
 /// var i = 0
 /// foo(&i) // Invalid conversion to UnsafePointer
 /// \endcode
-class AutoClosurePointerConversionFailure final : public FailureDiagnostic {
-  Type PointeeType;
-  Type PointerType;
-
+class AutoClosurePointerConversionFailure final : public ContextualFailure {
 public:
   AutoClosurePointerConversionFailure(Expr *root, ConstraintSystem &cs,
                                       Type pointeeType, Type pointerType,
                                       ConstraintLocator *locator)
-      : FailureDiagnostic(root, cs, locator), PointeeType(pointeeType),
-        PointerType(pointerType) {}
+      : ContextualFailure(root, cs, pointeeType, pointerType, locator) {}
 
   bool diagnoseAsError() override;
 };

lib/Sema/CSFix.cpp

@@ -271,7 +271,7 @@ AutoClosureForwarding *AutoClosureForwarding::create(ConstraintSystem &cs,
 
 bool AllowAutoClosurePointerConversion::diagnose(Expr *root, bool asNote) const {
   auto failure = AutoClosurePointerConversionFailure(root, getConstraintSystem(),
-      PointeeType, PointerType, getLocator());
+      getFromType(), getToType(), getLocator());
   return failure.diagnose(asNote);
 }
 

lib/Sema/CSFix.h

@@ -625,14 +625,11 @@ class AutoClosureForwarding final : public ConstraintFix {
                                        ConstraintLocator *locator);
 };
 
-class AllowAutoClosurePointerConversion final : public ConstraintFix {
-  Type PointeeType;
-  Type PointerType;
-
+class AllowAutoClosurePointerConversion final : public ContextualMismatch {
   AllowAutoClosurePointerConversion(ConstraintSystem &cs, Type pointeeType,
                                     Type pointerType, ConstraintLocator *locator)
-      : ConstraintFix(cs, FixKind::AllowAutoClosurePointerConversion, locator),
-        PointeeType(pointeeType), PointerType(pointerType) {}
+      : ContextualMismatch(cs, FixKind::AllowAutoClosurePointerConversion,
+                           pointeeType, pointerType, locator) {}
 
 public:
   std::string getName() const override {