[ASDAlexander77]

TSLANG_ISSUES.md 5: C++ overloads in @cpp classes.

A @cpp class can now declare a C++ overload set under its C++ name. Each method has its own @slot (or @linkname for a non-virtual one), and a call picks the overload from its arguments at compile time, as C++ does:

@cpp
class Methods {
    @slot(8) over(x: s32): s32;          // MSVC groups overloads in reverse declaration order
    @slot(7) over(x: f64): s32;
    @slot(6) over(a: s32, b: s32): s32;
    @linkname("?scaled@Methods@@QEAAHH@Z") scaled(x: s32): s32;
    @linkname("?scaled@Methods@@QEAAHN@Z") scaled(x: f64): s32;
}
methods.over(5); methods.over(2.5); methods.over(6, 7); methods.scaled(0.5);

Before, a second declaration of a name was a redefinition of symbol error. tsbindgen wrote scale_2, scale_3, so a binding regenerated after the header gained an overload silently called a different method.

How:

• mlirGenClassCppOverloadNames renames each overload after the first to name#N in the AST, so every name derived from it stays consistent; # can't appear in a TypeScript identifier. It runs once the base classes are known. A method in the slot of a base class's overload takes that overload's name, which is how it overrides it. It is idempotent across discovery and import passes.
• resolveCppOverload runs in mlirGenCallExpression once the arguments exist. It collects the overloads from the object's class and its bases, deduplicating overrides by name and slot. It scores each argument: 3 for its own type (number ≡ f64), 2 for integer→integer or float→float, 1 for any other conversion. It rebuilds the callee with ClassMethodAccess. No fit, or two equal best fits, is an error that lists the overloads.
• New errors:
  • an override of an overloaded base method without @slot;
  • a @slot overload with the same parameters as a base method in another slot. That keeps the existing slot_override error: it is the same method overridden in the wrong slot.
• DeclarationPrinter prints the declared name, and the importer renames again. @cpp diagnostics print declared names.
• tsbindgen keeps the C++ name for overloads; a method named like a field still gets _2. Docs updated: README, docs/cpp-classes.md, TSLANG_ISSUES.md item 5.

Tests:

• cppvtable/abi_host.cpp (real C++, built by the host compiler) gains:

  • virtual over(int), over(double), over(int, int);
  • non-virtual scaled(double);
  • pure-virtual Callback::pick(int) / pick(double) implemented in tslang and called from C++.

  test-jit-cppvtable-abi passes with MSVC locally. The Itanium slots (7/8/9, 5/6) and _ZN7Methods6scaledEd follow declaration order and the mangling rules, and Linux CI runs them. The Itanium compile tests check Counter's vtable, including pick and pick#1.

• 00cpp_overloads.ts: hand-made vtable, base and derived overloads, an override by slot, integer/float/u8/number/string arguments.

• Error tests: overload_no_match, overload_ambiguous, overload_override.

• export/import_cppvtable_class: overloads cross __decls, and the exporting module picks the same overload.

• TsClangImporterTests and the bindgen C++ test now use one name.

• Full Release suite: all passed, after updating the two tests that expected the old behavior (TsClangImporterTests, and the ownership verifier, which now skips 00cpp_overloads.ts like the other @cpp tests).

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