[tests] Add test data for KT-50827

compiler/testData/codegen/box/builderInference/issues/kt50827a.kt

@@ -0,0 +1,33 @@
+// ISSUE: KT-50827
+
+// IGNORE_LIGHT_ANALYSIS
+// IGNORE_BACKEND: ANY
+// REASON: red code (see corresponding diagnostic test)
+
+fun box(): String {
+    val box = ClassWithBoundedTypeParameter(
+        build {
+            setTypeVariable(TargetType())
+        }
+    )
+    consumeTargetTypeBuildee(box.buildee)
+    return "OK"
+}
+
+
+
+
+class TargetType
+
+fun consumeTargetTypeBuildee(value: Buildee<TargetType>) {}
+
+class ClassWithBoundedTypeParameter<T: Any>(val buildee: Buildee<T>)
+
+class Buildee<TV> {
+    fun setTypeVariable(value: TV) { storage = value }
+    private var storage: TV = TargetType() as TV
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}

compiler/testData/codegen/box/builderInference/issues/kt50827b.kt

@@ -0,0 +1,29 @@
+// ISSUE: KT-50827
+
+fun box(): String {
+    val box = ClassWithBoundedTypeParameter(
+        build {
+            setTypeVariable(TargetType())
+        }
+    )
+    consumeAnyBuildee(box.buildee)
+    return "OK"
+}
+
+
+
+
+class TargetType
+
+fun consumeAnyBuildee(value: Buildee<Any>) {}
+
+class ClassWithBoundedTypeParameter<T: Any>(val buildee: Buildee<T>)
+
+class Buildee<TV> {
+    fun setTypeVariable(value: TV) { storage = value }
+    private var storage: TV = TargetType() as TV
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}

compiler/testData/diagnostics/tests/builderInference/issues/kt50827.fir.kt

@@ -0,0 +1,30 @@
+// ISSUE: KT-50827
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val box = ClassWithBoundedTypeParameter(
+        build {
+            setTypeVariable(TargetType())
+        }
+    )
+    val buildee = box.buildee
+    // 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>>(<!ARGUMENT_TYPE_MISMATCH("Buildee<TargetType>; Buildee<kotlin.Any>")!>buildee<!>)
+}
+
+
+
+
+class TargetType
+
+class ClassWithBoundedTypeParameter<T: Any>(val buildee: Buildee<T>)
+
+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)
+}

compiler/testData/diagnostics/tests/builderInference/issues/kt50827.kt

@@ -0,0 +1,30 @@
+// ISSUE: KT-50827
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val box = ClassWithBoundedTypeParameter(
+        build {
+            setTypeVariable(TargetType())
+        }
+    )
+    val buildee = box.buildee
+    // 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>>(<!TYPE_MISMATCH("Buildee<TargetType>; Buildee<Any>"), TYPE_MISMATCH("Buildee<Any>; Buildee<TargetType>")!>buildee<!>)
+}
+
+
+
+
+class TargetType
+
+class ClassWithBoundedTypeParameter<T: Any>(val buildee: Buildee<T>)
+
+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)
+}