[clang-format] QualifierOrder does not reorder template arguments

[MyDeveloperDay]

Summary

https://github.com/llvm/llvm-project/issues/53981

Reorder the qualifiers inside the template argument. This should handle the simple cases of

<const T>
<T const>

But only by relaxing that single letter capital variables are not possible macros

Fixes: #53981

[curdeius]

LGTM. Thanks for fixing this!

clang/lib/Format/QualifierAlignmentFixer.cpp

344–346

[HazardyKnusperkeks]

clang/lib/Format/QualifierAlignmentFixer.cpp

480–482

Maybe?

clang/unittests/Format/QualifierFixerTest.cpp

910

As far as I understand stuff like <const Container> worked before? But maybe still add it as test case.

[curdeius]

clang/unittests/Format/QualifierFixerTest.cpp

910

It didn't work before at all.
+1 for adding a test with a longer name.

clang/lib/Format/QualifierAlignmentFixer.cpp

const FormatToken *LeftRightQualifierAlignmentFixer::analyzeRight(
   while (Qual && isQualifierOrType(Qual, ConfiguredQualifierTokens)) {
     LastQual = Qual;
     Qual = Qual->Next;
   }
   if (LastQual && Qual != LastQual) {
     rotateTokens(SourceMgr, Fixes, Tok, LastQual, /*Left=*/false);
     Tok = LastQual;
   } else if (Tok->startsSequence(QualifierType, tok::identifier,
+                                 TT_TemplateCloser)) {
+    FormatToken *Closer = Tok->Next->Next;
+    rotateTokens(SourceMgr, Fixes, Tok, Tok->Next, /*Left=*/false);
+    Tok = Closer;
+    return Tok;
+  } else if (Tok->startsSequence(QualifierType, tok::identifier,
                                  TT_TemplateOpener)) {
     // Read from the TemplateOpener to
     // TemplateCloser as in const ArrayRef<int> a; const ArrayRef<int> &a;
     FormatToken *EndTemplate = Tok->Next->Next->MatchingParen;
     if (EndTemplate) {
       // Move to the end of any template class members e.g.
       // `Foo<int>::iterator`.
       if (EndTemplate->startsSequence(TT_TemplateCloser, tok::coloncolon,
if (LastQual && Qual != LastQual && Qual->is(QualifierType)) {
     if (Tok->Next->Next && Tok->Next->Next->isOneOf(tok::identifier, tok::star,
                                                     tok::amp, tok::ampamp)) {
       // Don't swap `::iterator const` to `::const iterator`.
       if (!Tok->Previous ||
           (Tok->Previous && !Tok->Previous->is(tok::coloncolon))) {
         rotateTokens(SourceMgr, Fixes, Tok, Tok->Next, /*Left=*/true);
         Tok = Tok->Next;
       }
+    } else if (Tok->startsSequence(tok::identifier, QualifierType,
+                                   TT_TemplateCloser)) {
+      FormatToken *Closer = Tok->Next->Next;
+      rotateTokens(SourceMgr, Fixes, Tok, Tok->Next, /*Left=*/true);
+      Tok = Closer;
     }
   }
   if (Tok->is(TT_TemplateOpener) && Tok->Next &&
       (Tok->Next->is(tok::identifier) || Tok->Next->isSimpleTypeSpecifier()) &&
       Tok->Next->Next && Tok->Next->Next->is(QualifierType))
     rotateTokens(SourceMgr, Fixes, Tok->Next, Tok->Next->Next, /*Left=*/true);
   if (Tok->startsSequence(tok::identifier) && Tok->Next) {
     if (Tok->Previous &&
         Tok->Previous->isOneOf(tok::star, tok::ampamp, tok::amp))
       return Tok;
     const FormatToken *Next = Tok->Next;
     // The case  `std::Foo<T> const` -> `const std::Foo<T> &&`
     while (Next && Next->isOneOf(tok::identifier, tok::coloncolon))
       Next = Next->Next;
     if (Next && Next->Previous &&
         Next->Previous->startsSequence(tok::identifier, TT_TemplateOpener)) {
       // Read from to the end of the TemplateOpener to
       // TemplateCloser const ArrayRef<int> a; const ArrayRef<int> &a;
       if (Next->is(tok::comment) && Next->getNextNonComment())
         Next = Next->getNextNonComment();
       assert(Next->MatchingParen && "Missing template closer");
       Next = Next->MatchingParen;
+
+      // If the template closer is closing the requires clause,
+      // then stop and go back to the TemplateOpener and do whatever is
+      // inside the <>.
       if (Next->ClosesRequiresClause)
-        return Next;
+        return Next->MatchingParen;
       Next = Next->Next;
 
       // Move to the end of any template class members e.g.
       // `Foo<int>::iterator`.
       if (Next && Next->startsSequence(tok::coloncolon, tok::identifier))
         Next = Next->Next->Next;
       if (Next && Next->is(QualifierType)) {
         // Move the qualifier.

 // If a token is an identifier and it's upper case, it could
 // be a macro and hence we need to be able to ignore it.
 bool LeftRightQualifierAlignmentFixer::isPossibleMacro(const FormatToken *Tok) {
   if (!Tok)
     return false;
   if (!Tok->is(tok::identifier))
     return false;
   if (Tok->TokenText.upper() == Tok->TokenText.str())
-    return true;
+    // T,K,U,V likely could be template arguments
+    return (Tok->TokenText.size() != 1);
   return false;
 }
 
 } // namespace format
 } // namespace clang

clang/unittests/Format/QualifierFixerTest.cpp

verifyFormat("// clang-format off\n"
                "inline static const int a = 0;\n",
                "// clang-format off\n"
                "int const inline static a = 0;\n"
                "// clang-format on\n"
                "int const inline static a = 0;\n",
                Style);
 }
 
+TEST_F(QualifierFixerTest, TemplatesRight) {
+  FormatStyle Style = getLLVMStyle();
+  Style.QualifierAlignment = FormatStyle::QAS_Custom;
+  Style.QualifierOrder = {"type", "const"};
+
+  verifyFormat("template <typename T>\n"
+               "  requires Concept<T const>\n"
+               "void f();",
+               "template <typename T>\n"
+               "  requires Concept<const T>\n"
+               "void f();",
+               Style);
+  verifyFormat("TemplateType<T const> t;", "TemplateType<const T> t;", Style);
+  verifyFormat("TemplateType<Container const> t;",
+               "TemplateType<const Container> t;", Style);
+}
+
+TEST_F(QualifierFixerTest, TemplatesLeft) {
+  FormatStyle Style = getLLVMStyle();
+  Style.QualifierAlignment = FormatStyle::QAS_Custom;
+  Style.QualifierOrder = {"const", "type"};
+
+  verifyFormat("template <const T> t;", "template <T const> t;", Style);
+  verifyFormat("template <typename T>\n"
+               "  requires Concept<const T>\n"
+               "void f();",
+               "template <typename T>\n"
+               "  requires Concept<T const>\n"
+               "void f();",
+               Style);
+  verifyFormat("TemplateType<const T> t;", "TemplateType<T const> t;", Style);
+  verifyFormat("TemplateType<const Container> t;",
+               "TemplateType<Container const> t;", Style);
+}
+
 } // namespace format
 } // namespace clang