[CSFix] Add a specific kind for CollectionElementContextualMismatch

Author: xedin

include/swift/Sema/CSFix.h

@@ -365,6 +365,10 @@ enum class FixKind : uint8_t {
   /// Ignore either capability (read/write) or type mismatch in conversion
   /// between two key path types.
   IgnoreKeyPathContextualMismatch,
+
+  /// Ignore a type mismatch between deduced element type and externally
+  /// imposed one.
+  IgnoreCollectionElementContextualMismatch,
 };
 
 class ConstraintFix {
@@ -1845,7 +1849,9 @@ class RemoveReturn final : public ContextualMismatch {
 class CollectionElementContextualMismatch final : public ContextualMismatch {
   CollectionElementContextualMismatch(ConstraintSystem &cs, Type srcType,
                                       Type dstType, ConstraintLocator *locator)
-      : ContextualMismatch(cs, srcType, dstType, locator) {}
+      : ContextualMismatch(cs,
+                           FixKind::IgnoreCollectionElementContextualMismatch,
+                           srcType, dstType, locator) {}
 
 public:
   std::string getName() const override {
@@ -1857,6 +1863,10 @@ class CollectionElementContextualMismatch final : public ContextualMismatch {
   static CollectionElementContextualMismatch *
   create(ConstraintSystem &cs, Type srcType, Type dstType,
          ConstraintLocator *locator);
+
+  static bool classof(ConstraintFix *fix) {
+    return fix->getKind() == FixKind::IgnoreCollectionElementContextualMismatch;
+  }
 };
 
 class DefaultGenericArgument final : public ConstraintFix {

lib/Sema/CSSimplify.cpp

@@ -11689,7 +11689,8 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
   case FixKind::ContextualMismatch:
   case FixKind::IgnoreContextualType:
   case FixKind::IgnoreAssignmentDestinationType:
-  case FixKind::AllowConversionThroughInOut: {
+  case FixKind::AllowConversionThroughInOut:
+  case FixKind::IgnoreCollectionElementContextualMismatch: {
     auto impact = 1;
 
     auto locator = fix->getLocator();