Merge pull request #20495 from theblixguy/fix/SR-9213

[Sema] [CSDiag] Fixes incorrect diagnostic when using keypath with tuples

Author: xedin

include/swift/AST/DiagnosticsSema.def

@@ -510,6 +510,8 @@ ERROR(expr_string_interpolation_outside_string,none,
       "string interpolation can only appear inside a string literal", ())
 ERROR(unsupported_keypath_tuple_element_reference,none,
       "key path cannot reference tuple elements", ())
+ERROR(expr_keypath_unimplemented_tuple,none,
+      "key path support for tuples is not implemented", ())
 ERROR(expr_keypath_subscript_index_not_hashable, none,
       "subscript index of type %0 in a key path must be Hashable", (Type))
 ERROR(expr_smart_keypath_application_type_mismatch,none,

lib/Sema/CSDiag.cpp

@@ -6686,8 +6686,14 @@ static bool diagnoseKeyPathComponents(ConstraintSystem &CS, KeyPathExpr *KPE,
                                corrections);
 
       if (currentType)
-        TC.diagnose(componentNameLoc, diag::could_not_find_type_member,
-                    currentType, componentName);
+        if (isa<TupleType>(currentType.getPointer())) {
+          TC.diagnose(KPE->getLoc(), diag::expr_keypath_unimplemented_tuple);
+          isInvalid = true;
+          break;
+        }
+        else
+          TC.diagnose(componentNameLoc, diag::could_not_find_type_member,
+                      currentType, componentName);
       else
         TC.diagnose(componentNameLoc, diag::use_unresolved_identifier,
                     componentName, false);

test/expr/unary/keypath/keypath-unimplemented.swift

@@ -12,3 +12,13 @@ class C {
 // rdar://problem/32209039 - Improve diagnostic when unsupported tuple element references are used in key path literals
 let _ = \(Int, String).0 // expected-error {{key path cannot reference tuple elements}}
 let _ = \(a: Int, b: String).b // expected-error {{key path cannot reference tuple elements}}
+
+struct TupleKeypath {
+    let labeled: (foo: Int, bar: String)
+    let unlabeled: (Int, Int)
+}
+
+let _: KeyPath<TupleKeypath, Int> = \TupleKeypath.labeled.foo // expected-error {{key path support for tuples is not implemented}}
+let _: KeyPath<TupleKeypath, String> = \TupleKeypath.labeled.bar // expected-error {{key path support for tuples is not implemented}}
+let _: KeyPath<TupleKeypath, Int> = \TupleKeypath.unlabeled.0 // expected-error {{key path support for tuples is not implemented}}
+let _: KeyPath<TupleKeypath, String> = \TupleKeypath.unlabeled.1 // expected-error {{key path support for tuples is not implemented}}