Nested arrows with same-named untyped parameters can be instantiated

[ASDAlexander77]

Problem

docs/bugs/generic_in_generic.ts failed to compile:

function render(screenWidth, screenHeight) {
    const getPoint = (x, y) => {
        const recenterX = x => (x - (screenWidth / 2.0)) / 2.0 / screenWidth;
        const recenterY = y => -(y - (screenHeight / 2.0)) / 2.0 / screenHeight;
        return recenterX(x) + recenterY(y);
    }
    const v = getPoint(512, 384);   // error: can't instantiate function. '...afL2C22...' not all generic types can be identified

It needs all three of these: an untyped outer arrow, an untyped inner arrow whose parameter has the same name as one of the outer's, and a variable captured from the enclosing function. Renaming the inner x to z made it compile.

Cause

An untyped parameter makes its function generic in an implicit type parameter named TGenParam_<parameter name> (processTypeParametersFromFunctionParameters). The inner x therefore got the same type-parameter name as the outer x. When getPoint was instantiated with TGenParam_x = si32, that binding was in scope while the inner arrow was generated, so the inner arrow was named and registered as already specialized (...afL3C20...<si32>, with its captured screenWidth) while its type stayed (x: TGenParam_x) => .... resolveFunctionWithCapture then found the captures under that name and built a bound function with the still-generic type, and nothing instantiates a bound function, so the call failed. (Traced with -debug-only=mlir on the debug build.)

Fix

getParameterGenericTypeName also includes the function's source position in the name (TGenParam_x_<pos>), so nested functions' implicit type parameters can't collide. Both places that build the name (processTypeParametersFromFunctionParameters and processTypeArgumentsFromFunctionParameters) use the same signature, so they still agree.

Testing

• New 00nested_implicit_generics.ts (compile + JIT + rc/none corpus): the original render/getPoint case, an untyped outer function with a capturing same-named inner arrow, and a same-named pair without capture. The current release fails with the error above.
• docs/bugs/generic_in_generic.ts now prints 0, 0, 0.016276, done.
• Full ctest: 3919/3919 pass.

🤖 Generated with Claude Code