[clang-format] Correctly format variable templates.

[curdeius]

Summary

Fixes https://github.com/llvm/llvm-project/issues/54257.

[curdeius]

Reverting as it provoked bug https://github.com/llvm/llvm-project/issues/54374.

clang/lib/Format/TokenAnnotator.cpp

struct ScopedContextCreator {
     }
   };
 
   void modifyContext(const FormatToken &Current) {
     auto AssignmentStartsExpression = [&]() {
       if (Current.getPrecedence() != prec::Assignment)
         return false;
 
-      if (Line.First->isOneOf(tok::kw_template, tok::kw_using, tok::kw_return))
+      if (Line.First->isOneOf(tok::kw_using, tok::kw_return))
         return false;
+      if (Line.First->is(tok::kw_template)) {
+        // `template` keyword can start a variable template.
+        const FormatToken *Tok = Line.First->getNextNonComment();
+        assert(Tok); // Current token is on the same line.
+        if (Tok->isNot(TT_TemplateOpener)) {
+          // Explicit template instantiations do not have `<>`.
+          return false;
+        }
+
+        Tok = Tok->MatchingParen;
+        if (!Tok)
+          return false;
+        Tok = Tok->getNextNonComment();
+        if (!Tok)
+          return false;
+
+        if (Tok->isOneOf(tok::kw_class, tok::kw_enum, tok::kw_concept,
+                         tok::kw_struct, tok::kw_using))
+          return false;
+
+        return true;
+      }
 
       // Type aliases use `type X = ...;` in TypeScript and can be exported
       // using `export type ...`.
       if (Style.isJavaScript() &&
           (Line.startsWith(Keywords.kw_type, tok::identifier) ||
            Line.startsWith(tok::kw_export, Keywords.kw_type, tok::identifier)))
         return false;
 

clang/unittests/Format/FormatTest.cpp

TEST_F(FormatTest, UnderstandsDigraphs) {
   verifyFormat("int arr[5] = <%%>;");
   verifyFormat("int arr<:::qualified_variable:> = {};");
   verifyFormat("int arr[::qualified_variable] = <%%>;");
   verifyFormat("%:include <header>");
   verifyFormat("%:define A x##y");
   verifyFormat("#define A x%:%:y");
 }
 
+TEST_F(FormatTest, FormatsVariableTemplates) {
+  verifyFormat("inline bool var = is_integral_v<int> && is_signed_v<int>;");
+  verifyFormat("template <typename T> "
+               "inline bool var = is_integral_v<T> && is_signed_v<T>;");
+}
+
 } // namespace
 } // namespace format
 } // namespace clang

clang/unittests/Format/TokenAnnotatorTest.cpp

 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsEnums) {
   auto Tokens = annotate("enum E {};");
   EXPECT_EQ(Tokens.size(), 6u) << Tokens;
   EXPECT_TOKEN(Tokens[2], tok::l_brace, TT_EnumLBrace);
 }
 
+TEST_F(TokenAnnotatorTest, UnderstandsDefaultedAndDeletedFunctions) {
+  auto Tokens = annotate("auto operator<=>(const T &) const & = default;");
+  EXPECT_EQ(Tokens.size(), 14u) << Tokens;
+  EXPECT_TOKEN(Tokens[9], tok::amp, TT_PointerOrReference);
+
+  Tokens = annotate("template <typename T> void F(T) && = delete;");
+  EXPECT_EQ(Tokens.size(), 15u) << Tokens;
+  EXPECT_TOKEN(Tokens[10], tok::ampamp, TT_PointerOrReference);
+}
+
+TEST_F(TokenAnnotatorTest, UnderstandsVariables) {
+  auto Tokens =
+      annotate("inline bool var = is_integral_v<int> && is_signed_v<int>;");
+  EXPECT_EQ(Tokens.size(), 15u) << Tokens;
+  EXPECT_TOKEN(Tokens[8], tok::ampamp, TT_BinaryOperator);
+}
+
+TEST_F(TokenAnnotatorTest, UnderstandsVariableTemplates) {
+  auto Tokens =
+      annotate("template <typename T> "
+               "inline bool var = is_integral_v<int> && is_signed_v<int>;");
+  EXPECT_EQ(Tokens.size(), 20u) << Tokens;
+  EXPECT_TOKEN(Tokens[13], tok::ampamp, TT_BinaryOperator);
+}
+
 TEST_F(TokenAnnotatorTest, UnderstandsLBracesInMacroDefinition) {
   auto Tokens = annotate("#define BEGIN NS {");
   EXPECT_EQ(Tokens.size(), 6u) << Tokens;
   EXPECT_TOKEN(Tokens[4], tok::l_brace, TT_Unknown);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsDelete) {
   auto Tokens = annotate("delete (void *)p;");