Allow lifetime dependence inference on implicit initializers

Author: meg-gupta

include/swift/AST/DiagnosticsSema.def

@@ -7870,36 +7870,31 @@ ERROR(lifetime_dependence_only_on_function_method_init_result, none,
        "functions, methods, initializers", ())
 ERROR(lifetime_dependence_invalid_return_type, none,
       "lifetime dependence can only be specified on ~Escapable results", ())
- ERROR(lifetime_dependence_cannot_infer_ambiguous_candidate, none,
-      "cannot infer lifetime dependence, multiple parameters qualifiy as a candidate", ())
+ERROR(lifetime_dependence_cannot_infer_ambiguous_candidate, none,
+      "cannot infer lifetime dependence %0, multiple parameters qualifiy as a candidate", (StringRef))
  ERROR(lifetime_dependence_cannot_infer_no_candidates, none,
-       "cannot infer lifetime dependence, no parameters found that are "
-       "~Escapable or Escapable with a borrowing ownership",
+       "cannot infer lifetime dependence %0, no parameters found that are "
+       "~Escapable or Escapable with a borrowing ownership", (StringRef))
+ ERROR(lifetime_dependence_ctor_non_self_or_nil_return, none,
+       "expected nil or self as return values in an initializer with "
+       "lifetime dependent specifiers",
        ())
-ERROR(lifetime_dependence_ctor_non_self_or_nil_return, none,
-      "expected nil or self as return values in an initializer with "
-       "lifetime dependent specifiers", ())
-ERROR(lifetime_dependence_on_bitwise_copyable, none,
-      "invalid lifetime dependence on bitwise copyable type", ())
-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
-//===----------------------------------------------------------------------===//
-
-ERROR(transferring_unsupported_param_specifier, none,
-      "'%0' cannot be applied to a 'transferring' parameter", (StringRef))
-
-ERROR(transferring_only_on_parameters_and_results, none,
-      "'transferring' may only be used on parameters and results", ())
-ERROR(transferring_cannot_be_applied_to_tuple_elt, none,
-      "'transferring' cannot be applied to tuple elements", ())
-
+ ERROR(lifetime_dependence_on_bitwise_copyable, none,
+       "invalid lifetime dependence on bitwise copyable type", ())
+ ERROR(lifetime_dependence_cannot_be_applied_to_tuple_elt, none,
+       "lifetime dependence specifiers cannot be applied to tuple elements", ())
+
+ //===----------------------------------------------------------------------===//
+ //                             MARK: Transferring
+ //===----------------------------------------------------------------------===//
+
+ ERROR(transferring_unsupported_param_specifier, none,
+       "'%0' cannot be applied to a 'transferring' parameter", (StringRef))
+
+ ERROR(transferring_only_on_parameters_and_results, none,
+       "'transferring' may only be used on parameters and results", ())
+ ERROR(transferring_cannot_be_applied_to_tuple_elt, none,
+       "'transferring' cannot be applied to tuple elements", ())
 
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

lib/Sema/LifetimeDependence.cpp

@@ -425,10 +425,6 @@ LifetimeDependenceInfo::infer(AbstractFunctionDecl *afd, Type resultType) {
   if (cd && cd->isImplicit()) {
     if (cd->getParameters()->size() == 0) {
       return std::nullopt;
-    } else {
-      diags.diagnose(cd->getLoc(),
-                     diag::lifetime_dependence_cannot_infer_implicit_init);
-      return std::nullopt;
     }
   }
 
@@ -470,9 +466,16 @@ LifetimeDependenceInfo::infer(AbstractFunctionDecl *afd, Type resultType) {
       continue;
     }
     if (candidateParam) {
-      diags.diagnose(
-          returnLoc,
-          diag::lifetime_dependence_cannot_infer_ambiguous_candidate);
+      if (afd->getKind() == DeclKind::Constructor && afd->isImplicit()) {
+        diags.diagnose(
+            returnLoc,
+            diag::lifetime_dependence_cannot_infer_ambiguous_candidate,
+            "on implicit initializer");
+        return std::nullopt;
+      }
+      diags.diagnose(returnLoc,
+                     diag::lifetime_dependence_cannot_infer_ambiguous_candidate,
+                     "");
       return std::nullopt;
     }
     candidateParam = param;
@@ -481,8 +484,15 @@ LifetimeDependenceInfo::infer(AbstractFunctionDecl *afd, Type resultType) {
   }
 
   if (!candidateParam && !hasParamError) {
+    if (afd->getKind() == DeclKind::Constructor && afd->isImplicit()) {
+      diags.diagnose(returnLoc,
+                     diag::lifetime_dependence_cannot_infer_no_candidates,
+                     "on implicit initializer");
+      return std::nullopt;
+    }
     diags.diagnose(returnLoc,
-                   diag::lifetime_dependence_cannot_infer_no_candidates);
+                   diag::lifetime_dependence_cannot_infer_no_candidates,
+                   "");
     return std::nullopt;
   }
   return lifetimeDependenceInfo;

test/Sema/implicit_lifetime_dependence.swift

@@ -0,0 +1,25 @@
+// RUN: %target-typecheck-verify-swift -disable-availability-checking -enable-experimental-feature NonescapableTypes -enable-experimental-feature NoncopyableGenerics
+// REQUIRES: asserts
+
+struct BufferView : ~Escapable, ~Copyable {
+  let ptr: UnsafeRawBufferPointer
+  let c: Int
+  @_unsafeNonescapableResult
+  init(_ ptr: UnsafeRawBufferPointer, _ c: Int) {
+    self.ptr = ptr
+    self.c = c
+  }
+}
+
+struct ImplicitInit1 : ~Escapable { // expected-error{{cannot infer lifetime dependence on implicit initializer, no parameters found that are ~Escapable or Escapable with a borrowing ownership}}
+  let ptr: UnsafeRawBufferPointer
+}
+
+struct ImplicitInit2 : ~Escapable, ~Copyable {
+  let mbv: BufferView
+}
+
+struct ImplicitInit3 : ~Escapable, ~Copyable { // expected-error{{cannot infer lifetime dependence on implicit initializer, multiple parameters qualifiy as a candidate}}
+  let mbv1: BufferView
+  let mbv2: BufferView
+}