[PATCH] D147377: [clang-format] Don't allow variable decls to have trailing return arrows

[Emilia Dreamer via Phabricator via cfe-commits]

rymiel created this revision.
rymiel added a project: clang-format.
rymiel added reviewers: HazardyKnusperkeks, owenpan, MyDeveloperDay.
Herald added projects: All, clang.
Herald added a subscriber: cfe-commits.
rymiel requested review of this revision.

The heuristic for determining if an arrow is a trailing return arrow
looks for the auto keyword, along with parentheses. This isn't
sufficient, since it also triggers on variable declarations with an auto
type, and with an arrow operator.

This patch unsets the `auto` state when the annotator encounters the
equals sign of a variable declaration.

Fixes https://github.com/llvm/llvm-project/issues/61469


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D147377

Files:
  clang/lib/Format/TokenAnnotator.cpp
  clang/unittests/Format/TokenAnnotatorTest.cpp


Index: clang/unittests/Format/TokenAnnotatorTest.cpp
===================================================================
--- clang/unittests/Format/TokenAnnotatorTest.cpp
+++ clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -1468,6 +1468,72 @@
   EXPECT_TOKEN(Tokens[9], tok::colon, TT_GenericSelectionColon);
 }
 
+TEST_F(TokenAnnotatorTest, UnderstandsTrailingReturnArrow) {
+  auto Tokens = annotate("auto f() -> int;");
+  ASSERT_EQ(Tokens.size(), 8u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::arrow, TT_TrailingReturnArrow);
+
+  Tokens = annotate("auto operator->() -> int;");
+  ASSERT_EQ(Tokens.size(), 9u) << Tokens;
+  EXPECT_TOKEN(Tokens[2], tok::arrow, TT_OverloadedOperator);
+  EXPECT_TOKEN(Tokens[5], tok::arrow, TT_TrailingReturnArrow);
+
+  Tokens = annotate("auto operator++(int) -> int;");
+  ASSERT_EQ(Tokens.size(), 10u) << Tokens;
+  EXPECT_TOKEN(Tokens[6], tok::arrow, TT_TrailingReturnArrow);
+
+  Tokens = annotate("auto operator=() -> int;");
+  ASSERT_EQ(Tokens.size(), 9u) << Tokens;
+  EXPECT_TOKEN(Tokens[5], tok::arrow, TT_TrailingReturnArrow);
+
+  Tokens = annotate("auto operator=(int) -> int;");
+  ASSERT_EQ(Tokens.size(), 10u) << Tokens;
+  EXPECT_TOKEN(Tokens[6], tok::arrow, TT_TrailingReturnArrow);
+
+  Tokens = annotate("auto foo() -> auto { return Val; }");
+  ASSERT_EQ(Tokens.size(), 12u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::arrow, TT_TrailingReturnArrow);
+
+  Tokens = annotate("struct S { auto bar() const -> int; };");
+  ASSERT_EQ(Tokens.size(), 14u) << Tokens;
+  EXPECT_TOKEN(Tokens[8], tok::arrow, TT_TrailingReturnArrow);
+
+  // Not trailing return arrows
+  Tokens = annotate("auto a = b->c;");
+  ASSERT_EQ(Tokens.size(), 8u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::arrow, TT_Unknown);
+
+  Tokens = annotate("auto a = (b)->c;");
+  ASSERT_EQ(Tokens.size(), 10u) << Tokens;
+  EXPECT_TOKEN(Tokens[6], tok::arrow, TT_Unknown);
+
+  Tokens = annotate("auto a = b()->c;");
+  ASSERT_EQ(Tokens.size(), 10u) << Tokens;
+  EXPECT_TOKEN(Tokens[6], tok::arrow, TT_Unknown);
+
+  Tokens = annotate("auto a = b->c();");
+  ASSERT_EQ(Tokens.size(), 10u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::arrow, TT_Unknown);
+
+  Tokens = annotate("decltype(auto) a = b()->c;");
+  ASSERT_EQ(Tokens.size(), 13u) << Tokens;
+  EXPECT_TOKEN(Tokens[9], tok::arrow, TT_Unknown);
+
+  Tokens = annotate("void f() { auto a = b->c(); }");
+  ASSERT_EQ(Tokens.size(), 16u) << Tokens;
+  EXPECT_TOKEN(Tokens[9], tok::arrow, TT_Unknown);
+
+  Tokens = annotate("void f() { auto a = b()->c; }");
+  ASSERT_EQ(Tokens.size(), 16u) << Tokens;
+  EXPECT_TOKEN(Tokens[11], tok::arrow, TT_Unknown);
+
+  // Mixed
+  Tokens = annotate("auto f() -> int { auto a = b()->c; }");
+  ASSERT_EQ(Tokens.size(), 18u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::arrow, TT_TrailingReturnArrow);
+  EXPECT_TOKEN(Tokens[13], tok::arrow, TT_Unknown);
+}
+
 TEST_F(TokenAnnotatorTest, UnderstandsVerilogOperators) {
   auto Annotate = [this](llvm::StringRef Code) {
     return annotate(Code, getLLVMStyle(FormatStyle::LK_Verilog));
Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -1970,6 +1970,12 @@
         if (Current.getPrecedence() == prec::Assignment)
           Contexts.back().VerilogAssignmentFound = true;
       }
+      if (AutoFound && Current.is(tok::equal) && Current.Previous &&
+          Current.Previous->isNot(tok::kw_operator)) {
+        // AutoFound is only used for function declarations with `auto`. This
+        // looks like a variable declaration, so unset it.
+        AutoFound = false;
+      }
       Current.setType(TT_BinaryOperator);
     } else if (Current.is(tok::comment)) {
       if (Current.TokenText.startswith("/*")) {


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