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Kotlin: a memberless stub the Java side makes for a missing kotlin.* type is used by K2 (Function1.invoke unresolved)

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#76 1 comentario 0 reacciones 0 asignados Ver en GitHub

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Evaluación

Dificultad
5/5
Tiempo estimado
Más de una semana
Aptitud para principiantes
28/100
Tipo de issue
Error
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
java, kotlin
Área
compilers

Línea de trabajo

Reproduce with a Java source set that lacks kotlin-stdlib and mentions kotlin.jvm.functions.Function1, plus Kotlin that calls through Function1; the Java side logs ClassSymbolScanner stub creation. Existing kotlin-package tests in maddi-modification-prepwork and maddi-modification-link put the stdlib on both sides and will not catch this. Done is K2 preferring its own library model over a Java-created stub, or the mixed inspector refusing that classpath mismatch.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

front-end:kotlin

Corrected 2026-09-28, the same day it was filed. The first version said that any Java mention of Function1 breaks Kotlin calls. It does not. It happens only when the Java source set does not have kotlin-stdlib on its class path. Then the Java front end creates a memberless stub for kotlin.jvm.functions.Function1, and K2 resolves against that stub. With the stdlib jar as a dependency of the Java source set, the same fixture parses cleanly. The original trigger came from a test harness that put the stdlib on K2's path only.

What remains is a robustness issue, not a correctness one on a buildable project: a stub made by one front end is used by the other.

package k
class X { fun apply(f: (String) -> Unit, s: String) { f(s) } }
Java source beside it, Java source set WITHOUT kotlin-stdlib Kotlin apply
class X { } {f.invoke(s);}
class X { void unrelated(kotlin.jvm.functions.Function1<String, String> g) { } } k2-unresolved-call:f at 2:55
class X { void unrelated(kotlin.jvm.functions.Function0<String> g) { } } fine

The Java side logs WARN ClassSymbolScanner -- Creating stub type for …, and a Java file that calls a stubbed type is dropped (Dropping compilation unit … (unresolved symbol)). Both are visible. What is not visible is that the Kotlin half then silently loses every call through the stubbed type.

When it matters. It matters when a configuration is incomplete, for example a hand-assembled source-set configuration (as coil needs) that forgets the stdlib on the Java side. The failure lands in Kotlin code that is correct, far from the missing class-path entry.

Options. K2 could prefer its own library model over a stub the Java side created (a stub is marked as such), or the mixed inspector could refuse to run when a Java source set lacks the stdlib while a Kotlin source set in the same project has it.

Not pinned by a test: the tiers in maddi-modification-prepwork and maddi-modification-link (package kotlin) put the stdlib on both sides, as a real build does.

Lenguaje dominante
Java
Estrellas
1
Forks
1
Merge medio
2 h 51 min
PR fusionados (30 d)
3

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