Fix #19745 type alias anonymous class instantiation #24763
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When creating anonymous classes with `new T {}` where T is a type alias
like `type T[X] = SomeClass[X]`, the compiler was failing to infer type
parameters, resulting in "is not a class type" errors.
The fix adds special handling for HKTypeLambda types in both Typer and
Namer to create synthetic constructor applications for type parameter
inference, similar to how class parents are handled.
neko-kai
commented
Dec 15, 2025
| */ | ||
| def typedNewTemplateParent(tree: untpd.Tree, pt: Type)(using Context): Tree = | ||
| // First type with AnyTypeConstructorProto to check if it's a HKTypeLambda | ||
| val parentTpt = typedType(tree, AnyTypeConstructorProto) |
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I am not sure myself whether this is a great idea performance-wise
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Tried to avoid retyping in next commit
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When creating anonymous classes with
new T {}where T is a type alias liketype T[X] = SomeClass[X], the compiler was failing to infer type parameters, resulting in "is not a class type" errors.The fix adds special handling for HKTypeLambda types in both Typer and Namer to create synthetic constructor applications for type parameter inference, similar to how class parents are handled.