[clang-format] Don't move qualifiers past pointers-to-member

[rymiel]

Summary

Previously, given a pointer-to-member type such as Foo const Bar::*,
clang-format would see the const Bar:: part as a regular type name
with scope resolution operators, and with QualifierAlignment: Right it
would attempt to "fix" it, resulting in Foo Bar::const *, a syntax
error.

This patch no longer allows qualifiers to be moved across ::*.

Fixes https://github.com/llvm/llvm-project/issues/60898

[owenpan]

clang/lib/Format/QualifierAlignmentFixer.cpp

284–285

Or:

while (Next && (Next->is(tok::identifier) || (Next->is(tok::coloncolon) &&
           (!Next->Next || Next->Next->isNot(tok::star))))) {

Nevertheless, I'm okay if you don't make any change.

[MyDeveloperDay]

Thanks for doing this @rymiel, LGTM..

[MyDeveloperDay]

maybe we should cherry pick into 16?

[HazardyKnusperkeks]

In D144537#4145545, @MyDeveloperDay wrote:

maybe we should cherry pick into 16?

+1

[rymiel]

In D144537#4145545, @MyDeveloperDay wrote:

maybe we should cherry pick into 16?

It's up to one of you (mostly because I don't know how to do backports and I don't want to mess it up)

[owenpan]

In D144537#4152225, @rymiel wrote:

In D144537#4145545, @MyDeveloperDay wrote:

maybe we should cherry pick into 16?

I don't know how to do backports and I don't want to mess it up

It's easy. Just reopen the issue, add it to the release milestone, and add a /check-pick comment and the release:backport label. See also https://llvm.org/docs/GitHub.html#backporting-fixes-to-the-release-branches.

clang/lib/Format/QualifierAlignmentFixer.cpp

if (LastQual && Qual != LastQual) {
     FormatToken *Next = Tok->Next;
     // The case  `const Foo` -> `Foo const`
     // The case  `const ::Foo` -> `::Foo const`
     // The case  `const Foo *` -> `Foo const *`
     // The case  `const Foo &` -> `Foo const &`
     // The case  `const Foo &&` -> `Foo const &&`
     // The case  `const std::Foo &&` -> `std::Foo const &&`
     // The case  `const std::Foo<T> &&` -> `std::Foo<T> const &&`
-    while (Next && Next->isOneOf(tok::identifier, tok::coloncolon))
+    // However,  `const Bar::*` remains the same.
+    while (Next && Next->isOneOf(tok::identifier, tok::coloncolon) &&
+           !Next->startsSequence(tok::coloncolon, tok::star)) {
       Next = Next->Next;
+    }
     if (Next && Next->is(TT_TemplateOpener)) {
       Next = Next->MatchingParen;
       // Move to the end of any template class members e.g.
       // `Foo<int>::iterator`.
       if (Next && Next->startsSequence(TT_TemplateCloser, tok::coloncolon,
                                        tok::identifier)) {
         return Tok;
       }

clang/unittests/Format/QualifierFixerTest.cpp

verifyFormat("int const P;\n#if 0\n#else\n#endif",
                "const int P;\n#if 0\n#else\n#endif", Style);
 
   verifyFormat("unsigned long const a;", "const unsigned long a;", Style);
   verifyFormat("unsigned long long const a;", "const unsigned long long a;",
                Style);
 
   // don't adjust macros
   verifyFormat("const INTPTR a;", "const INTPTR a;", Style);
+
+  // Pointers to members
+  verifyFormat("int S::*a;", Style);
+  verifyFormat("int const S::*a;", "const int S:: *a;", Style);
+  verifyFormat("int const S::*const a;", "const int S::* const a;", Style);
+  verifyFormat("int A::*const A::*p1;", Style);
+  verifyFormat("float (C::*p)(int);", Style);
+  verifyFormat("float (C::*const p)(int);", Style);
+  verifyFormat("float (C::*p)(int) const;", Style);
+  verifyFormat("float const (C::*p)(int);", "const float (C::*p)(int);", Style);
 }
 
 TEST_F(QualifierFixerTest, LeftQualifier) {
   FormatStyle Style = getLLVMStyle();
   Style.QualifierAlignment = FormatStyle::QAS_Left;
   Style.QualifierOrder = {"inline", "static", "const", "volatile", "type"};
 
   verifyFormat("const int a;", Style);
TEST_F(QualifierFixerTest, LeftQualifier) {
 
   verifyFormat("const std::Foo", "const std::Foo", Style);
   verifyFormat("const std::Foo<>", "const std::Foo<>", Style);
   verifyFormat("const std::Foo < int", "const std::Foo<int", Style);
   verifyFormat("const std::Foo<int>", "const std::Foo<int>", Style);
 
   // don't adjust macros
   verifyFormat("INTPTR const a;", "INTPTR const a;", Style);
+
+  // Pointers to members
+  verifyFormat("int S::*a;", Style);
+  verifyFormat("const int S::*a;", "int const S:: *a;", Style);
+  verifyFormat("const int S::*const a;", "int const S::* const a;", Style);
+  verifyFormat("int A::*const A::*p1;", Style);
+  verifyFormat("float (C::*p)(int);", Style);
+  verifyFormat("float (C::*const p)(int);", Style);
+  verifyFormat("float (C::*p)(int) const;", Style);
+  verifyFormat("const float (C::*p)(int);", "float const (C::*p)(int);", Style);
 }
 
 TEST_F(QualifierFixerTest, ConstVolatileQualifiersOrder) {
   FormatStyle Style = getLLVMStyle();
   Style.QualifierAlignment = FormatStyle::QAS_Left;
   Style.QualifierOrder = {"inline", "static", "const", "volatile", "type"};
 
   // The Default