[Test] Add test for KT-63996

False-positive TYPE_MISMATCH in builder inference with captured types

compiler/testData/diagnostics/tests/inference/builderInference/stubTypes/capturedTypesId.fir.kt

@@ -0,0 +1,36 @@
+// !LANGUAGE: +UnrestrictedBuilderInference
+// !DIAGNOSTICS: -DEPRECATION -UNCHECKED_CAST -OPT_IN_IS_NOT_ENABLED
+// WITH_STDLIB
+// ISSUE: KT-63996
+
+// FILE: main.kt
+
+fun <R> build(block: TestInterface<R>.() -> Unit): R = TODO()
+
+interface TestInterface<R> {
+    fun emit(r: R)
+    fun getOut(): Inv<out R>
+}
+
+class Inv<T> {
+}
+
+fun <K> capture(x: Inv<K>): K = null as K
+fun <I> id(x: I): I = null as I
+
+fun main() {
+    build {
+        emit("")
+        // K is fixed into CapturedType(out NotFixed: TypeVariable(R)
+        capture(id(getOut())) // unexpected TYPE_MISMATCH (KT-63996)
+        // capture(getOut()) // OK!!!
+        Unit
+    }
+    build<String> {
+        emit("")
+        // K is fixed into CapturedType(out NotFixed: TypeVariable(R)
+        capture(id(getOut())) // OK!!!
+        // capture(getOut()) // OK!!!
+        Unit
+    }
+}

compiler/testData/diagnostics/tests/inference/builderInference/stubTypes/capturedTypesId.kt

@@ -0,0 +1,36 @@
+// !LANGUAGE: +UnrestrictedBuilderInference
+// !DIAGNOSTICS: -DEPRECATION -UNCHECKED_CAST -OPT_IN_IS_NOT_ENABLED
+// WITH_STDLIB
+// ISSUE: KT-63996
+
+// FILE: main.kt
+
+fun <R> build(block: TestInterface<R>.() -> Unit): R = TODO()
+
+interface TestInterface<R> {
+    fun emit(r: R)
+    fun getOut(): Inv<out R>
+}
+
+class Inv<T> {
+}
+
+fun <K> capture(x: Inv<K>): K = null as K
+fun <I> id(x: I): I = null as I
+
+fun main() {
+    build {
+        emit("")
+        // K is fixed into CapturedType(out NotFixed: TypeVariable(R)
+        capture(id(<!TYPE_MISMATCH, TYPE_MISMATCH!>getOut()<!>)) // unexpected TYPE_MISMATCH (KT-63996)
+        // capture(getOut()) // OK!!!
+        Unit
+    }
+    build<String> {
+        emit("")
+        // K is fixed into CapturedType(out NotFixed: TypeVariable(R)
+        capture(id(getOut())) // OK!!!
+        // capture(getOut()) // OK!!!
+        Unit
+    }
+}