[TypeChecker] Not warning element cast to unrelated for known collection types (Set,Array and Dictionary)

Author: LucianoPAlmeida

lib/Sema/CSFix.cpp

@@ -151,7 +151,7 @@ CoerceToCheckedCast *CoerceToCheckedCast::attempt(ConstraintSystem &cs,
     return nullptr;
 
   const auto castKind = TypeChecker::typeCheckCheckedCast(
-      fromType, toType, CheckedCastContextKind::None, cs.DC,
+      fromType, toType, CheckedCastContextKind::Coercion, cs.DC,
       SourceLoc(), coerceExpr->getSubExpr(), SourceRange());
 
   // Invalid cast.

lib/Sema/TypeCheckConstraints.cpp

@@ -3037,7 +3037,9 @@ CheckedCastKind TypeChecker::typeCheckCheckedCast(Type fromType,
                                                   Expr *fromExpr,
                                                   SourceRange diagToRange) {
   // Determine whether we should suppress diagnostics.
-  const bool suppressDiagnostics = contextKind == CheckedCastContextKind::None;
+  const bool suppressDiagnostics =
+      contextKind == CheckedCastContextKind::None ||
+      contextKind == CheckedCastContextKind::Coercion;
   assert((suppressDiagnostics || diagLoc.isValid()) &&
          "diagnostics require a valid source location");
 
@@ -3133,6 +3135,7 @@ CheckedCastKind TypeChecker::typeCheckCheckedCast(Type fromType,
 
         switch (contextKind) {
         case CheckedCastContextKind::None:
+        case CheckedCastContextKind::Coercion:
           llvm_unreachable("suppressing diagnostics");
 
         case CheckedCastContextKind::ForcedCast: {
@@ -3264,7 +3267,9 @@ CheckedCastKind TypeChecker::typeCheckCheckedCast(Type fromType,
       return castKind;
 
     case CheckedCastKind::Unresolved:
-      return failed();
+      if (contextKind == CheckedCastContextKind::Coercion)
+        return failed();
+      return castKind;
     }
     llvm_unreachable("invalid cast type");
   };
@@ -3295,15 +3300,17 @@ CheckedCastKind TypeChecker::typeCheckCheckedCast(Type fromType,
                                          BridgingCoercion);
         break;
 
+      case CheckedCastKind::Unresolved:
+        if (contextKind == CheckedCastContextKind::Coercion)
+          return failed();
+        LLVM_FALLTHROUGH;
+
       case CheckedCastKind::ArrayDowncast:
       case CheckedCastKind::DictionaryDowncast:
       case CheckedCastKind::SetDowncast:
       case CheckedCastKind::ValueCast:
         hasCast = true;
         break;
-
-      case CheckedCastKind::Unresolved:
-        return failed();
       }
 
       switch (typeCheckCheckedCast(fromKeyValue->second, toKeyValue->second,
@@ -3318,15 +3325,17 @@ CheckedCastKind TypeChecker::typeCheckCheckedCast(Type fromType,
                                          BridgingCoercion);
         break;
 
+      case CheckedCastKind::Unresolved:
+        if (contextKind == CheckedCastContextKind::Coercion)
+          return failed();
+        LLVM_FALLTHROUGH;
+
       case CheckedCastKind::ArrayDowncast:
       case CheckedCastKind::DictionaryDowncast:
       case CheckedCastKind::SetDowncast:
       case CheckedCastKind::ValueCast:
         hasCast = true;
         break;
-
-      case CheckedCastKind::Unresolved:
-        return failed();
       }
 
       if (hasCast) return CheckedCastKind::DictionaryDowncast;
@@ -3423,6 +3432,7 @@ CheckedCastKind TypeChecker::typeCheckCheckedCast(Type fromType,
     case CheckedCastContextKind::EnumElementPattern:
     case CheckedCastContextKind::IsExpr:
     case CheckedCastContextKind::None:
+    case CheckedCastContextKind::Coercion:
       break;
     }
   }

lib/Sema/TypeChecker.h

@@ -341,6 +341,9 @@ enum class CheckedCastContextKind {
   IsPattern,
   /// An enum-element pattern.
   EnumElementPattern,
+  /// Coerce to checked cast. Used when we verify if it is possible to
+  /// suggest to convert a coercion to a checked cast.
+  Coercion,
 };
 
 namespace TypeChecker {