[FIR] KT-55181: Ensure throw argument is Throwable

`TYPE_MISMATCH` in `throwJLException.fir.kt` appeared,
because in `throw Exn` the type of `Exn` is implicit Unit.
This is red code anyway.

^KT-55181 Fixed

Merge-request: KT-MR-8292
Merged-by: Nikolay Lunyak <Nikolay.Lunyak@jetbrains.com>

compiler/testData/diagnostics/tests/FunctionReturnTypes.fir.kt

@@ -156,7 +156,7 @@ fun illegalReturnIf(): Char {
 }
 
 fun returnNothing(): Nothing {
-    throw 1
+    throw <!TYPE_MISMATCH!>1<!>
 }
 fun f(): Int {
     if (1 < 2) { return 1 } else returnNothing()

compiler/testData/diagnostics/tests/kt55181.kt

@@ -0,0 +1,5 @@
+// FIR_IDENTICAL
+
+fun main() {
+  throw <!TYPE_MISMATCH!>"str"<!>
+}

compiler/testData/diagnostics/tests/kt55181.txt

@@ -0,0 +1,3 @@
+package
+
+public fun main(): kotlin.Unit

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/throw.fir.kt

@@ -1,25 +0,0 @@
-// FILE: J.java
-
-import org.jetbrains.annotations.*;
-
-public class J {
-    @NotNull
-    public static Exception staticNN;
-    @Nullable
-    public static Exception staticN;
-    public static Exception staticJ;
-}
-
-// FILE: k.kt
-
-fun test() {
-    throw J.staticNN
-}
-
-fun test1() {
-    throw J.staticN
-}
-
-fun test2() {
-    throw J.staticJ
-}

compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/throw.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: J.java
 
 import org.jetbrains.annotations.*;

compiler/testData/diagnostics/tests/typealias/throwJLException.fir.kt

@@ -0,0 +1,7 @@
+// +JDK
+
+typealias Exn = java.lang.Exception
+
+fun test() {
+    throw <!NO_COMPANION_OBJECT, TYPE_MISMATCH!>Exn<!>
+}

compiler/testData/diagnostics/tests/typealias/throwJLException.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // +JDK
 
 typealias Exn = java.lang.Exception