Raise an error on namespace aliases with qualified names. #86122

katzdm · 2024-03-21T14:14:06Z

Clang's current behavior is to ignore the trailing qualifiers, but the grammar for namespace-alias-definition requires an identifier without qualification.

https://godbolt.org/z/1zvW5q4f8

github-actions · 2024-03-21T14:14:23Z

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llvmbot · 2024-03-21T14:14:57Z

@llvm/pr-subscribers-testing-tools

@llvm/pr-subscribers-clang

Author: Daniel M. Katz (katzdm)

Changes

Clang's current behavior is to ignore the trailing qualifiers, but the grammar for namespace-alias-definition requires an identifier without qualification.

https://godbolt.org/z/1zvW5q4f8

Full diff: https://github.com/llvm/llvm-project/pull/86122.diff

3 Files Affected:

(modified) clang/include/clang/Basic/DiagnosticParseKinds.td (+2)
(modified) clang/lib/Parse/ParseDeclCXX.cpp (+5)
(modified) clang/test/SemaCXX/namespace-alias.cpp (+2)

diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index 816c3ff5f8b2aa..d45a1f0b6ad1c0 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -268,6 +268,8 @@ def err_expected_semi_after_namespace_name : Error<
   "expected ';' after namespace name">;
 def err_unexpected_namespace_attributes_alias : Error<
   "attributes cannot be specified on namespace alias">;
+def err_unexpected_qualified_namespace_alias : Error<
+  "unexpected nested name specifier in namespace alias definition">;
 def err_unexpected_nested_namespace_attribute : Error<
   "attributes cannot be specified on a nested namespace definition">;
 def err_inline_namespace_alias : Error<"namespace alias cannot be inline">;
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 77d2382ea6d907..0ef2f2fad2a9d1 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -140,6 +140,11 @@ Parser::DeclGroupPtrTy Parser::ParseNamespace(DeclaratorContext Context,
       SkipUntil(tok::semi);
       return nullptr;
     }
+    if (!ExtraNSs.empty()) {
+      Diag(IdentLoc, diag::err_unexpected_qualified_namespace_alias);
+      SkipUntil(tok::semi);
+      return nullptr;
+    }
     if (attrLoc.isValid())
       Diag(attrLoc, diag::err_unexpected_namespace_attributes_alias);
     if (InlineLoc.isValid())
diff --git a/clang/test/SemaCXX/namespace-alias.cpp b/clang/test/SemaCXX/namespace-alias.cpp
index 281ee9962e8b52..10d2e8beeccaa0 100644
--- a/clang/test/SemaCXX/namespace-alias.cpp
+++ b/clang/test/SemaCXX/namespace-alias.cpp
@@ -47,6 +47,8 @@ namespace I {
   namespace A1 { int i; }
   
   namespace A2 = A1;
+
+  namespace A3::extra::specifiers = A2;  // expected-error {{unexpected nested name specifier}}
 }
 
 int f() {

Sirraide

Thanks for contributing! This needs a release note (in clang/docs/ReleaseNotes.rst) and some changes to the diagnostics, but other than that it looks fine to me.

clang/include/clang/Basic/DiagnosticParseKinds.td

clang/lib/Parse/ParseDeclCXX.cpp

katzdm · 2024-03-21T15:46:01Z

@Sirraide Thanks for the quick review! I've applied your feedback. Here is an example error message with the patch applied:

test.cpp:4:20: error: namespace alias must be a single identifier
    4 |     namespace alias::extra::qualifiers = ::myns;
      |                    ^~~~~~~~~~~~~~~~~~~
1 error generated.

Oops, still need the release note.

Sirraide · 2024-03-21T16:33:51Z

test.cpp:4:20: error: namespace alias must be a single identifier
    4 |     namespace alias::extra::qualifiers = ::myns;
      |                    ^~~~~~~~~~~~~~~~~~~
1 error generated.

Nice, that is pretty much exactly what I had in mind.

Sirraide

LGTM except for a minor comment wrt the release note.

clang/docs/ReleaseNotes.rst

Sirraide · 2024-03-21T16:36:01Z

You can ignore the merge conflicts in the release notes; it’s better to let whoever ends up merging this (probably me) take care of that when it comes to the release notes (because they get updated constantly).

Current behavior is to ignore the trailing qualifiers, but the grammar for `namespace-alias-definition` requires an `identifier` without qualification. https://godbolt.org/z/1zvW5q4f8 https://eel.is/c++draft/namespace.alias#nt:namespace-alias-definition

llvm/utils/lit/lit/formats/googletest.py

github-actions · 2024-03-21T16:38:30Z

✅ With the latest revision this PR passed the Python code formatter.

katzdm · 2024-03-21T16:42:02Z

You can ignore the merge conflicts in the release notes; it’s better to let whoever ends up merging this (probably me) take care of that when it comes to the release notes (because they get updated constantly).

Ah, missed this - already fixed it. Will ignore if it happens again.

Sirraide · 2024-03-21T16:45:36Z

You can ignore the merge conflicts in the release notes; it’s better to let whoever ends up merging this (probably me) take care of that when it comes to the release notes (because they get updated constantly).

Ah, missed this - already fixed it. Will ignore if it happens again.

I mean, no-one’s gonna be mad at you for fixing that yourself because it means less work for them; just saying that merging release notes is fairly trivial, so whoever merges it can just do that when they merge the pr—at least that’s my opinion on this. Otherwise, you’d have to keep resolving merge conflicts because they might come back time and time again if a pr stays open for a while.

github-actions · 2024-03-22T23:08:30Z

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llvmbot added clang Clang issues not falling into any other category clang:frontend Language frontend issues, e.g. anything involving "Sema" labels Mar 21, 2024

Sirraide requested changes Mar 21, 2024

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clang/include/clang/Basic/DiagnosticParseKinds.td Outdated Show resolved Hide resolved

clang/lib/Parse/ParseDeclCXX.cpp Outdated Show resolved Hide resolved

Sirraide requested changes Mar 21, 2024

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clang/docs/ReleaseNotes.rst Outdated Show resolved Hide resolved

llvmbot added llvm-lit testing-tools labels Mar 21, 2024

katzdm added 2 commits March 21, 2024 12:36

Addressing feedback.

e40b7af

Sirraide requested changes Mar 21, 2024

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llvm/utils/lit/lit/formats/googletest.py Outdated Show resolved Hide resolved

Sirraide removed llvm-lit testing-tools labels Mar 21, 2024

Add release notes.

4f65d91

Fix release note.

3c6632e

katzdm force-pushed the disallow-qualified-ns-alises branch from c5997ee to 3c6632e Compare March 21, 2024 16:40

Sirraide approved these changes Mar 21, 2024

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Sirraide merged commit 0024875 into llvm:main Mar 22, 2024

katzdm deleted the disallow-qualified-ns-alises branch March 22, 2024 23:13

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Raise an error on namespace aliases with qualified names. #86122

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