Look up operator overloads by CXXOperatorName in GetFunctionsUsingName

[guitargeek]

GetFunctionsUsingName built its lookup key only as an identifier, so queries like "operator==" never matched: operator overloads live in the AST under CXXOperatorName, not under an Identifier. cppyy's namespace getattr fallback (Cppyy::GetMethodsFromName -> Cpp::GetFunctionsUsingName) therefore returned no candidates and getattr(ns, 'operator==') raised AttributeError.

Detect names that start with "operator" followed by a non-identifier character and match the trimmed suffix against OperatorKinds.def. When it matches, build the DeclarationName via getCXXOperatorName(OO_...); otherwise fall back to the identifier lookup. Covers symbolic and multi-token overloads (==, +, (), [], new, delete, new[], delete[], ...). Names that merely start with "operator" (e.g. "operators_count") are left on the identifier path because the next character is an identifier-continue.

Fixes compiler-research/cppyy#219.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.80%. Comparing base (1ea28e2) to head (b43f9a6).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #996      +/-   ##
==========================================
+ Coverage   82.78%   82.80%   +0.02%     
==========================================
  Files          15       15              
  Lines        5048     5055       +7     
==========================================
+ Hits         4179     4186       +7     
  Misses        869      869              

Files with missing lines	Coverage Δ
lib/CppInterOp/CppInterOp.cpp	88.98% <100.00%> (+0.02%)	⬆️

Files with missing lines	Coverage Δ
lib/CppInterOp/CppInterOp.cpp	88.98% <100.00%> (+0.02%)	⬆️

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[vgvassilev]

Can we use LookupOperatorName instead of the string comparisons?

Something similar to:

clang/lib/Sema/SemaCoroutine.cpp-829-ExprResult Sema::BuildOperatorCoawaitLookupExpr(Scope *S, SourceLocation Loc) {
clang/lib/Sema/SemaCoroutine.cpp-830-  DeclarationName OpName =
clang/lib/Sema/SemaCoroutine.cpp-831-      Context.DeclarationNames.getCXXOperatorName(OO_Coawait);
clang/lib/Sema/SemaCoroutine.cpp-832-  LookupResult Operators(*this, OpName, SourceLocation(),
clang/lib/Sema/SemaCoroutine.cpp:833:                         Sema::LookupOperatorName);
clang/lib/Sema/SemaCoroutine.cpp-834-  LookupName(Operators, S);