`Expected FirResolvedTypeRef with ConeKotlinType but was FirUserTypeRefImpl`

Component

• github-workflows-kt (library with the DSL)
• bindings server (https://bindings.krzeminski.it)
• I don't know

Action

Just run CI for this project - looking at the step, it's about compiling the script: https://github.com/typesafegithub/github-workflows-kt/actions/runs/27213769566/job/80485705899

Expected

Succeeds.

Actual

Fails with

error: while analysing .github/workflows/end-to-end-tests.main.kts:37:5: org.jetbrains.kotlin.utils.exceptions.KotlinIllegalArgumentExceptionWithAttachments: Expected FirResolvedTypeRef with ConeKotlinType but was FirUserTypeRefImpl (end-to-end-tests.main.kts): org.jetbrains.kotlin.util.FileAnalysisException: While analysing .github/workflows/end-to-end-tests.main.kts:37:5: org.jetbrains.kotlin.utils.exceptions.KotlinIllegalArgumentExceptionWithAttachments: Expected FirResolvedTypeRef with ConeKotlinType but was FirUserTypeRefImpl

Most likely related to a bug in Kotlin 2.4.0, see KT-86352. Slack thread: https://kotlinlang.slack.com/archives/C0BT46EL8/p1780927673531079?thread_ts=1773078486.658489&cid=C0BT46EL8

Workaround, if exists

In your workflow, add:

@file:DependsOn("fwilhe2:setup-kotlin:v1")

import io.github.typesafegithub.workflows.actions.fwilhe2.SetupKotlin

// ...

workflow(
    // ...
    consistencyCheckJobConfig = DEFAULT_CONSISTENCY_CHECK_JOB_CONFIG.copy(
        // ...
        additionalSteps = {
            uses(
                name = "Downgrade Kotlin",
                action = SetupKotlin(
                    // One version before 2.4.0 that contains a bug leading to this failure:
                    //   While analysing .github/workflows/build.main.kts:53:13:
                    //   org.jetbrains.kotlin.utils.exceptions.KotlinIllegalArgumentExceptionWithAttachments:
                    //   Expected FirResolvedTypeRef with ConeKotlinType but was FirUserTypeRefImpl
                    // This downgrade is meant to be a temporary workaround.
                    version = "2.3.21",
                ),
            )
        },
    ),

Example PR: https://github.com/typesafegithub/github-workflows-kt/pull/2350

Start with the linked CI run and .github/workflows/end-to-end-tests.main.kts, especially line 37. Compare the Kotlin 2.4.0 failure with the documented 2.3.21 workaround, then review KT-86352 and PR #2350. Done means the workflow compiles and CI succeeds without the reported FIR error.