[clang] aea60ab - [clang-format] Make bitwise and imply requires clause (#110942)

[via cfe-commits]

Author: Emilia Kond
Date: 2024-10-22T13:36:28+03:00
New Revision: aea60ab94db4729bad17daa86ccfc411d48a1699

URL: https://github.com/llvm/llvm-project/commit/aea60ab94db4729bad17daa86ccfc411d48a1699
DIFF: https://github.com/llvm/llvm-project/commit/aea60ab94db4729bad17daa86ccfc411d48a1699.diff

LOG: [clang-format] Make bitwise and imply requires clause (#110942)

This patch adjusts the requires clause/expression parser to imply a
requires clause if it is preceded by a bitwise and operator `&`, and
assume it is a reference qualifier. The justification is that bitwise
operations should not be used for requires expressions.

This is a band-aid fix. The real problems lie in the lookahead heuristic
in the same method. It may be worth it to rewrite that whole heuristic
to track more state in the future, instead of just blindly marching
forward across multiple unrelated definitions, since right now, the
definition following the one with the requires clause can influence
whether the heuristic chooses clause or expression.

Fixes https://github.com/llvm/llvm-project/issues/110485

Added: 
    

Modified: 
    clang/lib/Format/UnwrappedLineParser.cpp
    clang/unittests/Format/TokenAnnotatorTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 4a5109983dfcc5..0b74889a6b20cd 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -3484,10 +3484,10 @@ bool UnwrappedLineParser::parseRequires() {
   case tok::r_paren:
   case tok::kw_noexcept:
   case tok::kw_const:
+  case tok::amp:
     // This is a requires clause.
     parseRequiresClause(RequiresToken);
     return true;
-  case tok::amp:
   case tok::ampamp: {
     // This can be either:
     // if (... && requires (T t) ...)

diff  --git a/clang/unittests/Format/TokenAnnotatorTest.cpp b/clang/unittests/Format/TokenAnnotatorTest.cpp
index 60deae0c9b1129..da195ccb6f6dbd 100644
--- a/clang/unittests/Format/TokenAnnotatorTest.cpp
+++ b/clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -1318,6 +1318,15 @@ TEST_F(TokenAnnotatorTest, UnderstandsRequiresClausesAndConcepts) {
   Tokens = annotate("bool x = t && requires(Foo<C1 || C2> x) { x.foo(); };");
   ASSERT_EQ(Tokens.size(), 25u) << Tokens;
   EXPECT_TOKEN(Tokens[5], tok::kw_requires, TT_RequiresExpression);
+
+  // Second function definition is required due to lookahead
+  Tokens = annotate("void f() &\n"
+                    "  requires(n == 1)\n"
+                    "{}\n"
+                    "void g();");
+  ASSERT_EQ(Tokens.size(), 19u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::amp, TT_PointerOrReference);
+  EXPECT_TOKEN(Tokens[5], tok::kw_requires, TT_RequiresClause);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsRequiresExpressions) {