[tests] Add test data for KT-56949

compiler/testData/codegen/box/builderInference/issues/kt56949.kt

@@ -0,0 +1,34 @@
+// ISSUE: KT-56949
+
+// IGNORE_LIGHT_ANALYSIS
+// IGNORE_BACKEND_K1: ANY
+// REASON: red code (see corresponding diagnostic test)
+
+// IGNORE_BACKEND_K2: JVM_IR, WASM
+// REASON: run-time failure (java.lang.ClassCastException: TargetType cannot be cast to DifferentType @ Kt56949Kt$box$1.invoke)
+
+fun box(): String {
+    build {
+        setTypeVariable(TargetType())
+        consumeDifferentTypeSubtype(getTypeVariable())
+    }
+    return "OK"
+}
+
+
+
+
+class TargetType
+class DifferentType
+
+fun <T: DifferentType> consumeDifferentTypeSubtype(value: T) {}
+
+class Buildee<TV> {
+    fun setTypeVariable(value: TV) { storage = value }
+    fun getTypeVariable(): TV = storage
+    private var storage: TV = TargetType() as TV
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}