From 1515e63864ec781c7d751fe66144923a923df1a9 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano@gmail.com>
Date: Wed, 2 Oct 2024 19:06:56 -0700
Subject: [PATCH] [clang-format] Handle template closer followed by empty
 paretheses (#110408)

Fixes #109925.
---
 clang/lib/Format/TokenAnnotator.cpp           | 42 ++++++++++---------
 clang/lib/Format/UnwrappedLineParser.cpp      | 12 ++++--
 clang/unittests/Format/TokenAnnotatorTest.cpp |  7 ++++
 3 files changed, 38 insertions(+), 23 deletions(-)

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 4512e539cc7947..ad9ed7b47d002c 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -189,25 +189,29 @@ class AnnotatingParser {
       next();
     }
 
-    for (bool SeenTernaryOperator = false; CurrentToken;) {
+    for (bool SeenTernaryOperator = false, MaybeAngles = true; CurrentToken;) {
       const bool InExpr = Contexts[Contexts.size() - 2].IsExpression;
       if (CurrentToken->is(tok::greater)) {
         const auto *Next = CurrentToken->Next;
-        // Try to do a better job at looking for ">>" within the condition of
-        // a statement. Conservatively insert spaces between consecutive ">"
-        // tokens to prevent splitting right bitshift operators and potentially
-        // altering program semantics. This check is overly conservative and
-        // will prevent spaces from being inserted in select nested template
-        // parameter cases, but should not alter program semantics.
-        if (Next && Next->is(tok::greater) &&
-            Left->ParentBracket != tok::less &&
-            CurrentToken->getStartOfNonWhitespace() ==
-                Next->getStartOfNonWhitespace().getLocWithOffset(-1)) {
-          return false;
-        }
-        if (InExpr && SeenTernaryOperator &&
-            (!Next || !Next->isOneOf(tok::l_paren, tok::l_brace))) {
-          return false;
+        if (CurrentToken->isNot(TT_TemplateCloser)) {
+          // Try to do a better job at looking for ">>" within the condition of
+          // a statement. Conservatively insert spaces between consecutive ">"
+          // tokens to prevent splitting right shift operators and potentially
+          // altering program semantics. This check is overly conservative and
+          // will prevent spaces from being inserted in select nested template
+          // parameter cases, but should not alter program semantics.
+          if (Next && Next->is(tok::greater) &&
+              Left->ParentBracket != tok::less &&
+              CurrentToken->getStartOfNonWhitespace() ==
+                  Next->getStartOfNonWhitespace().getLocWithOffset(-1)) {
+            return false;
+          }
+          if (InExpr && SeenTernaryOperator &&
+              (!Next || !Next->isOneOf(tok::l_paren, tok::l_brace))) {
+            return false;
+          }
+          if (!MaybeAngles)
+            return false;
         }
         Left->MatchingParen = CurrentToken;
         CurrentToken->MatchingParen = Left;
@@ -243,11 +247,11 @@ class AnnotatingParser {
       // operator that was misinterpreted because we are parsing template
       // parameters.
       // FIXME: This is getting out of hand, write a decent parser.
-      if (InExpr && !Line.startsWith(tok::kw_template) &&
+      if (MaybeAngles && InExpr && !Line.startsWith(tok::kw_template) &&
           Prev.is(TT_BinaryOperator)) {
         const auto Precedence = Prev.getPrecedence();
         if (Precedence > prec::Conditional && Precedence < prec::Relational)
-          return false;
+          MaybeAngles = false;
       }
       if (Prev.isOneOf(tok::question, tok::colon) && !Style.isProto())
         SeenTernaryOperator = true;
@@ -1615,7 +1619,7 @@ class AnnotatingParser {
         return false;
       break;
     case tok::greater:
-      if (Style.Language != FormatStyle::LK_TextProto)
+      if (Style.Language != FormatStyle::LK_TextProto && Tok->is(TT_Unknown))
         Tok->setType(TT_BinaryOperator);
       if (Tok->Previous && Tok->Previous->is(TT_TemplateCloser))
         Tok->SpacesRequiredBefore = 1;
diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 7813d86ff0ea10..f7b3561f6e0335 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -2551,7 +2551,7 @@ bool UnwrappedLineParser::parseParens(TokenType AmpAmpTokenType) {
         parseChildBlock();
       break;
     case tok::r_paren: {
-      const auto *Prev = LeftParen->Previous;
+      auto *Prev = LeftParen->Previous;
       if (!MightBeStmtExpr && !MightBeFoldExpr && !Line->InMacroBody &&
           Style.RemoveParentheses > FormatStyle::RPS_Leave) {
         const auto *Next = Tokens->peekNextToken();
@@ -2575,9 +2575,13 @@ bool UnwrappedLineParser::parseParens(TokenType AmpAmpTokenType) {
           FormatTok->Optional = true;
         }
       }
-      if (Prev && Prev->is(TT_TypenameMacro)) {
-        LeftParen->setFinalizedType(TT_TypeDeclarationParen);
-        FormatTok->setFinalizedType(TT_TypeDeclarationParen);
+      if (Prev) {
+        if (Prev->is(TT_TypenameMacro)) {
+          LeftParen->setFinalizedType(TT_TypeDeclarationParen);
+          FormatTok->setFinalizedType(TT_TypeDeclarationParen);
+        } else if (Prev->is(tok::greater) && FormatTok->Previous == LeftParen) {
+          Prev->setFinalizedType(TT_TemplateCloser);
+        }
       }
       nextToken();
       return SeenEqual;
diff --git a/clang/unittests/Format/TokenAnnotatorTest.cpp b/clang/unittests/Format/TokenAnnotatorTest.cpp
index dd58fbc70cb91e..2f09b380a87134 100644
--- a/clang/unittests/Format/TokenAnnotatorTest.cpp
+++ b/clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -3394,6 +3394,13 @@ TEST_F(TokenAnnotatorTest, SplitPenalty) {
   EXPECT_SPLIT_PENALTY(Tokens[7], 23u);
 }
 
+TEST_F(TokenAnnotatorTest, TemplateInstantiation) {
+  auto Tokens = annotate("return FixedInt<N | M>();");
+  ASSERT_EQ(Tokens.size(), 11u) << Tokens;
+  EXPECT_TOKEN(Tokens[2], tok::less, TT_TemplateOpener);
+  EXPECT_TOKEN(Tokens[6], tok::greater, TT_TemplateCloser);
+}
+
 } // namespace
 } // namespace format
 } // namespace clang