[tests] Add test data for KT-60291

compiler/testData/diagnostics/tests/builderInference/issues/kt60291b.kt

@@ -0,0 +1,26 @@
+// ISSUE: KT-60291
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = if (true)
+        build <!BUILDER_INFERENCE_MULTI_LAMBDA_RESTRICTION!>{ setTypeVariable(TargetType()) }<!>
+    else
+        build <!BUILDER_INFERENCE_MULTI_LAMBDA_RESTRICTION!>{}<!>
+    // 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)
+}
+
+
+
+
+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)
+}