[PATCH] D142738: Warn if _Optional used at top-level of decl

[Christopher Bazley via Phabricator via cfe-commits]

chrisbazley created this revision.
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Parameter declarations using [] syntax can be
written more naturally using an _Optional
qualifier than using Clang's _Nullable
annotation, e.g.

void myfunc(_Optional const char s[]);
// s may be a null pointer

With the above exception, it isn't useful to
declare a non-pointed-to object as _Optional
(although so-qualified types exist during
expression evaluation). Such declarations are
therefore disallowed, like equivalent abuse of
the restrict qualifier, to avoid confusion.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D142738

Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaDecl.cpp
  clang/lib/Sema/SemaType.cpp


Index: clang/lib/Sema/SemaType.cpp
===================================================================
--- clang/lib/Sema/SemaType.cpp
+++ clang/lib/Sema/SemaType.cpp
@@ -5807,6 +5807,16 @@
     }
   }
 
+  // Types other than those of a pointed-to object or pointed-to incomplete 
type
+  // shall not be _Optional-qualified in a declaration.
+  if (T.isOptionalQualified() && !IsTypedefName &&
+      (!T->isArrayType() || !D.isPrototypeContext())) {
+    S.Diag(D.getDeclSpec().getOptionalSpecLoc(),
+           diag::err_typecheck_invalid_optional_not_pointee)
+        << T;
+    Context.getNonOptionalType(T);
+  }
+
   // Apply any undistributed attributes from the declaration or declarator.
   ParsedAttributesView NonSlidingAttrs;
   for (ParsedAttr &AL : D.getDeclarationAttributes()) {
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -5088,6 +5088,13 @@
       Diag(DS.getRestrictSpecLoc(),
            diag::err_typecheck_invalid_restrict_not_pointer_noarg)
            << DS.getSourceRange();
+
+    // Types other than those of a pointed-to object or pointed-to incomplete
+    // type shall not be _Optional-qualified in a declaration.
+    if (TypeQuals & DeclSpec::TQ_optional)
+      Diag(DS.getOptionalSpecLoc(),
+           diag::err_typecheck_invalid_optional_not_pointee_noarg)
+          << DS.getSourceRange();
   }
 
   if (DS.isInlineSpecified())
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5930,6 +5930,10 @@
   "restrict requires a pointer or reference">;
 def err_typecheck_invalid_restrict_invalid_pointee : Error<
   "pointer to function type %0 may not be 'restrict' qualified">;
+def err_typecheck_invalid_optional_not_pointee : Error<
+  "_Optional is only valid on a pointed-to object or incomplete type (%0 is 
invalid)">;
+def err_typecheck_invalid_optional_not_pointee_noarg : Error<
+  "_Optional is only valid on a pointed-to object or incomplete type">;
 def ext_typecheck_zero_array_size : Extension<
   "zero size arrays are an extension">, InGroup<ZeroLengthArray>;
 def err_typecheck_zero_array_size : Error<



Index: clang/lib/Sema/SemaType.cpp
===================================================================
--- clang/lib/Sema/SemaType.cpp
+++ clang/lib/Sema/SemaType.cpp
@@ -5807,6 +5807,16 @@
     }
   }
 
+  // Types other than those of a pointed-to object or pointed-to incomplete type
+  // shall not be _Optional-qualified in a declaration.
+  if (T.isOptionalQualified() && !IsTypedefName &&
+      (!T->isArrayType() || !D.isPrototypeContext())) {
+    S.Diag(D.getDeclSpec().getOptionalSpecLoc(),
+           diag::err_typecheck_invalid_optional_not_pointee)
+        << T;
+    Context.getNonOptionalType(T);
+  }
+
   // Apply any undistributed attributes from the declaration or declarator.
   ParsedAttributesView NonSlidingAttrs;
   for (ParsedAttr &AL : D.getDeclarationAttributes()) {
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -5088,6 +5088,13 @@
       Diag(DS.getRestrictSpecLoc(),
            diag::err_typecheck_invalid_restrict_not_pointer_noarg)
            << DS.getSourceRange();
+
+    // Types other than those of a pointed-to object or pointed-to incomplete
+    // type shall not be _Optional-qualified in a declaration.
+    if (TypeQuals & DeclSpec::TQ_optional)
+      Diag(DS.getOptionalSpecLoc(),
+           diag::err_typecheck_invalid_optional_not_pointee_noarg)
+          << DS.getSourceRange();
   }
 
   if (DS.isInlineSpecified())
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5930,6 +5930,10 @@
   "restrict requires a pointer or reference">;
 def err_typecheck_invalid_restrict_invalid_pointee : Error<
   "pointer to function type %0 may not be 'restrict' qualified">;
+def err_typecheck_invalid_optional_not_pointee : Error<
+  "_Optional is only valid on a pointed-to object or incomplete type (%0 is invalid)">;
+def err_typecheck_invalid_optional_not_pointee_noarg : Error<
+  "_Optional is only valid on a pointed-to object or incomplete type">;
 def ext_typecheck_zero_array_size : Extension<
   "zero size arrays are an extension">, InGroup<ZeroLengthArray>;
 def err_typecheck_zero_array_size : Error<

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