No TypeParameter found for index T

[Scogun]

Describe the bug
After upgrade from 1.18.1 version to 2.0.0 I started to face an issue No TypeParameter found for index T

To Reproduce
I had next code:

(this.declaration as KSClassDeclaration).getAllSuperTypes().any { it.toClassName() == ITERABLE }

I started to face next issue:

KSType 'Comparable<String>' has type arguments, which are not supported for ClassName conversion. Use KSType.toTypeName().

After switching on toTypeName I face No TypeParameter found for index T

(this.declaration as KSClassDeclaration).getAllSuperTypes().any { it.toTypeName() == ITERABLE }

Expected behavior
toTypeName should work for wide generic classes.

Additional context
Maybe I don't see the reason why toTypeName requests TypeParameterResolver.

[ZacSweers]

Can you offer a minimally reproducing sample? This isn't really actionable on the current details offered

[Scogun]

The problem is introduced here.
I used toClassName for any classes. Right now it fails for generic ones.
I can change this code:

(this.declaration as KSClassDeclaration).getAllSuperTypes().any { it.toClassName() == ITERABLE }

to

(this.declaration as KSClassDeclaration).getAllSuperTypes().any { (it.declaration as KSClassDeclaration).toClassName() == ITERABLE }

but it also will fail here:

sourceType.toClassName() == STRING

if sourceType is generic.
It brings a lot of additional checkings.

[JakeWharton]

What we are asking for is a minimally-reproducing sample for the toTypeName crash.

[Scogun]

I know. It's just hard to make a small sample while it happens into kotlinpoet-ksp. So, I tried to explain.

[Brendon-Mendicino]

HI, having a similar issue, but i think the problem might be with KSP. I checked and when you evaluate the arguments in an annotation annotationType.resolved().arguments where it is declared in a different package, the argument is evaluated to the type parameter name (the actual one), this is my output for arguments=[INVARIANT E]. Then when you try to convert an annotation using toAnnotationSpec() the processor crashes.

let me know if I could be of any help, I might give you a branch of my code where this is error is happening and then you might take a look at it

[eyupcanakman]

Here's a minimal case that triggers the toTypeName crash.

class Subject<T> : Comparable<T>

// in a SymbolProcessor
subject.superTypes.forEach { it.resolve().toTypeName() }
// java.util.NoSuchElementException: No TypeParameter found for index T

The no-arg KSType.toTypeName() defaults its resolver to TypeParameterResolver.EMPTY, so the bare T from the Comparable<T> supertype hits EMPTY.get("T") and throws. toAnnotationSpec() reaches the same path after #1956 switched the annotation type to the no-resolver toTypeName().

Two directions for the fix, not sure which you'd prefer here. Resolve the type parameter from the type's own declaration when the supplied resolver misses, or keep EMPTY strict and pass a real resolver at the call sites #1956 changed. Any preference?