[clang-format] Don't modify template arguments on the LHS of assignment

[rymiel]

Summary

After clang-format has determined that an equals sign starts an
expression, it will also go backwards and modify any star/amp/ampamp
binary operators on the left side of the assignment to be
pointers/references instead.

There already exists logic to skip over contents of parentheses and
square brackets, but this patch also expands that logic to apply to
angle brackets. This is so that binary operators inside of template
arguments would not be touched, primary arguments to non-type template
parameters.

Fixes https://github.com/llvm/llvm-project/issues/62055

clang/lib/Format/TokenAnnotator.cpp

void modifyContext(const FormatToken &Current) {
 
     if (AssignmentStartsExpression()) {
       Contexts.back().IsExpression = true;
       if (!Line.startsWith(TT_UnaryOperator)) {
         for (FormatToken *Previous = Current.Previous;
              Previous && Previous->Previous &&
              !Previous->Previous->isOneOf(tok::comma, tok::semi);
              Previous = Previous->Previous) {
-          if (Previous->isOneOf(tok::r_square, tok::r_paren)) {
+          if (Previous->isOneOf(tok::r_square, tok::r_paren, tok::greater)) {
             Previous = Previous->MatchingParen;
             if (!Previous)
               break;
           }
           if (Previous->opensScope())
             break;
           if (Previous->isOneOf(TT_BinaryOperator, TT_UnaryOperator) &&
               Previous->isOneOf(tok::star, tok::amp, tok::ampamp) &&

clang/unittests/Format/TokenAnnotatorTest.cpp

TEST_F(TokenAnnotatorTest, UnderstandsUsesOfStarAndAmp) {
   Tokens = annotate("template <typename T, typename U = T&&> struct S {};");
   ASSERT_EQ(Tokens.size(), 17u) << Tokens;
   EXPECT_TOKEN(Tokens[9], tok::ampamp, TT_PointerOrReference);
 
   Tokens = annotate("template <typename T = int (*)(int)> struct S {};");
   ASSERT_EQ(Tokens.size(), 19u) << Tokens;
   EXPECT_TOKEN(Tokens[6], tok::l_paren, TT_FunctionTypeLParen);
   EXPECT_TOKEN(Tokens[7], tok::star, TT_PointerOrReference);
+
+  Tokens = annotate("Foo<A && B> a = {};");
+  ASSERT_EQ(Tokens.size(), 12u) << Tokens;
+  EXPECT_TOKEN(Tokens[3], tok::ampamp, TT_BinaryOperator);
+
+  Tokens = annotate("Foo<A &&> a = {};");
+  ASSERT_EQ(Tokens.size(), 11u) << Tokens;
+  EXPECT_TOKEN(Tokens[3], tok::ampamp, TT_PointerOrReference);
+
+  Tokens = annotate("template <enable_if_t<foo && !bar>* = nullptr> void f();");
+  ASSERT_EQ(Tokens.size(), 19u) << Tokens;
+  EXPECT_TOKEN(Tokens[5], tok::ampamp, TT_BinaryOperator);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsUsesOfPlusAndMinus) {
   auto Tokens = annotate("x - 0");
   ASSERT_EQ(Tokens.size(), 4u) << Tokens;
   EXPECT_TOKEN(Tokens[1], tok::minus, TT_BinaryOperator);
   Tokens = annotate("0 + 0");
   ASSERT_EQ(Tokens.size(), 4u) << Tokens;