[tests] Add test data for KT-60291

compiler/testData/diagnostics/tests/builderInference/issues/kt60291a.fir.kt

@@ -0,0 +1,29 @@
+// ISSUE: KT-60291
+// CHECK_TYPE_WITH_EXACT
+// WITH_STDLIB
+
+fun test() {
+    val buildee = selectBuildee(
+        build { setTypeVariable(TargetType()) },
+        build {}
+    )
+    // exact type equality check — turns unexpected compile-time behavior into red code
+    // considered to be non-user-reproducible code for the purposes of these tests
+    checkExactType<Buildee<TargetType>>(buildee)
+}
+
+
+
+
+fun <T> selectBuildee(vararg values: Buildee<T>): Buildee<T> = values.first()
+
+class TargetType
+
+class Buildee<TV> {
+    fun setTypeVariable(value: TV) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}