Ban lifetime dependence specifiers on tuple result

Author: meg-gupta

include/swift/AST/DiagnosticsSema.def

@@ -7849,6 +7849,8 @@ ERROR(lifetime_dependence_cannot_infer_implicit_init, none,
       "cannot infer lifetime dependence on implicit initializer of ~Escapable"
       " type, define an initializer with explicit lifetime dependence"
       " specifiers", ())
+ERROR(lifetime_dependence_cannot_be_applied_to_tuple_elt, none,
+      "lifetime dependence specifiers cannot be applied to tuple elements", ())
 
 //===----------------------------------------------------------------------===//
 //                             MARK: Transferring

lib/Sema/TypeCheckType.cpp

@@ -5048,6 +5048,11 @@ TypeResolver::resolveResultDependsOnTypeRepr(ResultDependsOnTypeRepr *repr,
 
 NeverNullType TypeResolver::resolveLifetimeDependentReturnTypeRepr(
     LifetimeDependentReturnTypeRepr *repr, TypeResolutionOptions options) {
+  if (options.is(TypeResolverContext::TupleElement)) {
+    diagnoseInvalid(repr, repr->getSpecifierLoc(),
+                    diag::lifetime_dependence_cannot_be_applied_to_tuple_elt);
+    return ErrorType::get(getASTContext());
+  }
   if (!options.is(TypeResolverContext::FunctionResult)) {
     diagnoseInvalid(
         repr, repr->getSpecifierLoc(),

test/SIL/implicit_lifetime_dependence.swift

@@ -160,3 +160,9 @@ struct GenericBufferView<Element> : ~Escapable {
     }
   }
 }
+
+// CHECK: sil hidden @$s28implicit_lifetime_dependence23tupleLifetimeDependenceyAA10BufferViewV_ADtADYlsF : $@convention(thin) (@guaranteed BufferView) -> _scope(1) (@owned BufferView, @owned BufferView) {
+func tupleLifetimeDependence(_ x: borrowing BufferView) -> (BufferView, BufferView) {
+  return (BufferView(x.ptr, x.c), BufferView(x.ptr, x.c))
+}
+

test/Sema/explicit_lifetime_dependence_specifiers.swift

@@ -1,4 +1,5 @@
 // RUN: %target-typecheck-verify-swift -disable-availability-checking -enable-experimental-feature NonescapableTypes -disable-experimental-parser-round-trip   -enable-experimental-feature NoncopyableGenerics -enable-builtin-module -enable-experimental-feature BitwiseCopyable
+// REQUIRES: asserts
 // REQUIRES: noncopyable_generics
 import Builtin
 
@@ -97,6 +98,10 @@ func invalidSpecifierPosition2(_ x: borrowing BufferView) -> BufferView {
   return BufferView(y.ptr)
 }
 
+func invalidTupleLifetimeDependence(_ x: inout BufferView) -> (_mutate(x) BufferView, BufferView) { // expected-error{{lifetime dependence specifiers cannot be applied to tuple elements}}
+  return (BufferView(x.ptr), BufferView(x.ptr))
+}
+
 struct Wrapper : ~Escapable {
   let view: BufferView
   init(_ view: consuming BufferView) {