Backport "Only rename method type params shadowing enclosing class type params" to 3.8.0 #24809
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WojciechMazur
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Previously, method type parameters were always renamed if they had the same name as any class type parameter, regardless of whether the class type parameter was actually used in the method signature. As a result, we rename methods's type params for unnecessary names like: #24671 (Note that renaming actually doesn't cause binary incompatibility, and this change is just for make generic signature a bit clear and silence false-positive MIMA reporting). For example, in an example below, the Scala compiler rename the generic signature of `bar` to something like `bar[T1](x: T1): T1` because `T` is used by `Foo[T]`. However, this is unnessary rename because none of T in method signature refer the `T` of `Foo[T]`. ```scala class Foo[T]: def bar[T](x: T): T = ??? ``` This commit makes the renaming conditional: Method type parameters are only renamed when - (1) A class type parameter is referenced in the method signature, and - (2) That class type parameter is shadowed by a method type parameter [Cherry-picked a93c849]
[Cherry-picked 3d4d397]
Co-authored-by: Lukas Rytz <[email protected]> [Cherry-picked 7cc63d4]
Move isTypeParameterInMethSig as a local function and simplify it: collecting method type parameters by checking owner directly instead of searching the initialSymbol's typeParams list. [Cherry-picked e7fa00c]
Add test cases for nested class generic signatures when method type parameters shadow enclosing class type parameters. The tests verify that Scala 3 correctly handles type parameter name conflicts in nested generic classes by renaming method-level type parameters to avoid clashing with outer class type parameters. Closes #24619 [Cherry-picked 1e392ee]
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December 22, 2025 11:05
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Backports #24684 to the 3.8.0-RC4.
PR submitted by the release tooling.
[skip ci]