Add test for KT-54742

compiler/testData/diagnostics/tests/inference/coercionToUnit/afterBareReturn.fir.kt

@@ -0,0 +1,41 @@
+interface I
+open class C
+
+fun completed(): String = "..."
+
+fun <T> incomplete(): T = null!!
+
+fun <T : I> incompatibleI(): T = null!!
+fun <T : C> incompatibleC(): T = null!!
+
+val p = false
+
+fun expectUnit(x: Unit) = x
+
+fun test1() = run {
+    if (p) return@run
+    completed() // ok, not returned
+}
+
+fun test2() = run {
+    if (p) return@run
+    incomplete() // ? either uninferred T or Unit
+}
+
+fun test3() = run {
+    if (p) return@run
+    incompatibleI() // ? either uninferred T or error (Unit </: I)
+}
+
+fun test4() = <!INFERRED_TYPE_VARIABLE_INTO_EMPTY_INTERSECTION!>run<!> {
+    if (p) return@run
+    incompatibleC() // ? either uninferred T or error (Unit </: C)
+}
+
+fun main() {
+    // all ok
+    expectUnit(<!ARGUMENT_TYPE_MISMATCH!>test1()<!>)
+    expectUnit(test2())
+    expectUnit(test3())
+    expectUnit(test4())
+}

compiler/testData/diagnostics/tests/inference/coercionToUnit/afterBareReturn.kt

@@ -0,0 +1,41 @@
+interface I
+open class C
+
+fun completed(): String = "..."
+
+fun <T> incomplete(): T = null!!
+
+fun <T : I> incompatibleI(): T = null!!
+fun <T : C> incompatibleC(): T = null!!
+
+val p = false
+
+fun expectUnit(x: Unit) = x
+
+fun test1() = run {
+    if (p) return@run
+    completed() // ok, not returned
+}
+
+fun test2() = run {
+    if (p) return@run
+    incomplete() // ? either uninferred T or Unit
+}
+
+fun test3() = <!INFERRED_TYPE_VARIABLE_INTO_POSSIBLE_EMPTY_INTERSECTION!>run<!> {
+    if (p) return@run
+    incompatibleI() // ? either uninferred T or error (Unit </: I)
+}
+
+fun test4() = <!INFERRED_TYPE_VARIABLE_INTO_EMPTY_INTERSECTION_WARNING!>run<!> {
+    if (p) return@run
+    incompatibleC() // ? either uninferred T or error (Unit </: C)
+}
+
+fun main() {
+    // all ok
+    expectUnit(test1())
+    expectUnit(test2())
+    expectUnit(test3())
+    expectUnit(test4())
+}

compiler/testData/diagnostics/tests/inference/coercionToUnit/afterBareReturn.txt

@@ -0,0 +1,26 @@
+package
+
+public val p: kotlin.Boolean = false
+public fun completed(): kotlin.String
+public fun expectUnit(/*0*/ x: kotlin.Unit): kotlin.Unit
+public fun </*0*/ T : C> incompatibleC(): T
+public fun </*0*/ T : I> incompatibleI(): T
+public fun </*0*/ T> incomplete(): T
+public fun main(): kotlin.Unit
+public fun test1(): kotlin.Unit
+public fun test2(): kotlin.Unit
+public fun test3(): kotlin.Unit
+public fun test4(): kotlin.Unit
+
+public open class C {
+    public constructor C()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface I {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}