[clang-format] [PR43531] clang-format damages "alternative representations" for operators

[MyDeveloperDay]

Summary

https://bugs.llvm.org/show_bug.cgi?id=43531

Fix for clang-format incorrectly handles "alternative operators" as described by https://en.cppreference.com/w/cpp/language/operator_alternative

compl = ~
not = !

these are unary operators, and clang-format will remove the space between them and a numeric constant

this incorrectly formats the following code

int a compl 5;
int a not 5;

into:

int a compl5;
int a not5;

The code adds FIXME unit tests for "alternative token" representations for {} [] and # as defined by the same link, which would require a more detailed change to the FormatTokenLexer

[mitchell-stellar]

clang/lib/Format/TokenAnnotator.cpp

2904

Without context, "compl5" and "not5" do not make sense. Can you try to rephrase this comment?

2908

For consistency, Left.TokenText == "not" may be better. I cannot find another instance of .equals().

clang/unittests/Format/FormatTest.cpp

14613

Instead of using a URL link, perhaps describe in words what this test is supposed to do?

[MyDeveloperDay]

• add additional compl(5) and not(5) unit tests
• improve the comments around the condition and explaining the tests
• remove the use of .equals(...)

[mitchell-stellar]

LGTM

clang/lib/Format/TokenAnnotator.cpp

if (Right.is(tok::colon)) {
     if (Right.is(TT_InlineASMColon) && Left.is(tok::coloncolon))
       return false;
     if (Right.is(TT_DictLiteral))
       return Style.SpacesInContainerLiterals;
     if (Right.is(TT_AttributeColon))
       return false;
     return true;
   }
-  if (Left.is(TT_UnaryOperator))
+  if (Left.is(TT_UnaryOperator)) {
+    // The alternative operators for ~ and ! are "compl" and "not".
+    // If they are used instead, we do not want to combine them with
+    // the token to the right, unless that is a left paren.
+    if (!Right.is(tok::l_paren)) {
+      if (Left.is(tok::exclaim) && Left.TokenText == "not")
+        return true;
+      if (Left.is(tok::tilde) && Left.TokenText == "compl")
+        return true;
+    }
     return (Style.SpaceAfterLogicalNot && Left.is(tok::exclaim)) ||
            Right.is(TT_BinaryOperator);
+  }
 
   // If the next token is a binary operator or a selector name, we have
   // incorrectly classified the parenthesis as a cast. FIXME: Detect correctly.
   if (Left.is(TT_CastRParen))
     return Style.SpaceAfterCStyleCast ||
            Right.isOneOf(TT_BinaryOperator, TT_SelectorName);
 
   if (Left.is(tok::greater) && Right.is(tok::greater)) {

clang/unittests/Format/FormatTest.cpp

TEST_F(FormatTest, AmbersandInLamda) {
   // Test case reported in https://bugs.llvm.org/show_bug.cgi?id=41899
   FormatStyle AlignStyle = getLLVMStyle();
   AlignStyle.PointerAlignment = FormatStyle::PAS_Left;
   verifyFormat("auto lambda = [&a = a]() { a = 2; };", AlignStyle);
   AlignStyle.PointerAlignment = FormatStyle::PAS_Right;
   verifyFormat("auto lambda = [&a = a]() { a = 2; };", AlignStyle);
 }
 
+TEST_F(FormatTest, AlternativeOperators) {
+  // Test case for ensuring alternate operators are not
+  // combined with their right most neighbour.
+  verifyFormat("int a and b;");
+  verifyFormat("int a and_eq b;");
+  verifyFormat("int a bitand b;");
+  verifyFormat("int a bitor b;");
+  verifyFormat("int a compl b;");
+  verifyFormat("int a not b;");
+  verifyFormat("int a not_eq b;");
+  verifyFormat("int a or b;");
+  verifyFormat("int a xor b;");
+  verifyFormat("int a xor_eq b;");
+  verifyFormat("return this not_eq bitand other;");
+  verifyFormat("bool operator not_eq(const X bitand other)");
+
+  verifyFormat("int a and 5;");
+  verifyFormat("int a and_eq 5;");
+  verifyFormat("int a bitand 5;");
+  verifyFormat("int a bitor 5;");
+  verifyFormat("int a compl 5;");
+  verifyFormat("int a not 5;");
+  verifyFormat("int a not_eq 5;");
+  verifyFormat("int a or 5;");
+  verifyFormat("int a xor 5;");
+  verifyFormat("int a xor_eq 5;");
+
+  verifyFormat("int a compl(5);");
+  verifyFormat("int a not(5);");
+
+  /* FIXME handle alternate tokens
+   * https://en.cppreference.com/w/cpp/language/operator_alternative
+  // alternative tokens
+  verifyFormat("compl foo();");     //  ~foo();
+  verifyFormat("foo() <%%>;");      // foo();
+  verifyFormat("void foo() <%%>;"); // void foo(){}
+  verifyFormat("int a <:1:>;");     // int a[1];[
+  verifyFormat("%:define ABC abc"); // #define ABC abc
+  verifyFormat("%:%:");             // ##
+  */
+}
+
 } // end namespace
 } // end namespace format
 } // end namespace clang