[tests] Add test data for KT-57707

compiler/testData/codegen/box/builderInference/issues/kt57707.kt

@@ -0,0 +1,33 @@
+// ISSUE: KT-57707
+
+// IGNORE_LIGHT_ANALYSIS
+// IGNORE_BACKEND_K1: ANY
+// REASON: red code (see corresponding diagnostic test)
+
+fun box(): String {
+    build {
+        setTypeVariable(TargetType())
+        extensionSetOutProjectedTypeVariable(DifferentType())
+    }
+    return "OK"
+}
+
+
+
+
+class TargetType
+class DifferentType
+
+class Buildee<TV> {
+    fun setTypeVariable(value: TV) { storage = value }
+    private var storage: TV = TargetType() as TV
+}
+
+fun <ETV> Buildee<out ETV>.extensionSetOutProjectedTypeVariable(value: ETV) {
+    this as Buildee<ETV>
+    setTypeVariable(value)
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}

compiler/testData/diagnostics/tests/builderInference/issues/kt57707.fir.kt

@@ -0,0 +1,29 @@
+// ISSUE: KT-57707
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = build {
+        setTypeVariable(TargetType())
+        extensionSetOutProjectedTypeVariable(DifferentType())
+    }
+    // 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 DifferentType
+
+class Buildee<TV> {
+    fun setTypeVariable(value: TV) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <ETV> Buildee<out ETV>.extensionSetOutProjectedTypeVariable(value: ETV) {}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}

compiler/testData/diagnostics/tests/builderInference/issues/kt57707.kt

@@ -0,0 +1,29 @@
+// ISSUE: KT-57707
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = build {
+        setTypeVariable(TargetType())
+        <!RECEIVER_TYPE_MISMATCH("DifferentType; TargetType")!>extensionSetOutProjectedTypeVariable<!>(DifferentType())
+    }
+    // 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 DifferentType
+
+class Buildee<TV> {
+    fun setTypeVariable(value: TV) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <ETV> Buildee<out ETV>.extensionSetOutProjectedTypeVariable(value: ETV) {}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}