Resolve variable declaration in 'when' subject

compiler/testData/diagnostics/tests/when/withSubjectVariable/invisibleOutsideOfWhen.kt

@@ -0,0 +1,14 @@
+// !LANGUAGE: +VariableDeclarationInWhenSubject
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+fun foo(): Any = 42
+
+fun test(x: Any) {
+    val z1 = when (val y = foo()) {
+        42 -> "Magic: $y, $x"
+        else -> {
+            "Not magic: $y, $x"
+        }
+    }
+    val z2 = "Anyway, it was $<!UNRESOLVED_REFERENCE!>y<!>"
+}

compiler/testData/diagnostics/tests/when/withSubjectVariable/invisibleOutsideOfWhen.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(): kotlin.Any
+public fun test(/*0*/ x: kotlin.Any): kotlin.Unit

compiler/testData/diagnostics/tests/when/withSubjectVariable/shadowingOtherVariable.kt

@@ -0,0 +1,11 @@
+// !LANGUAGE: +VariableDeclarationInWhenSubject
+// !DIAGNOSTICS: -UNUSED_VARIABLE -UNUSED_PARAMETER
+
+fun foo(): Any = 42
+
+fun test(y: Any) {
+    val z = when (val <!NAME_SHADOWING!>y<!> = foo()) {
+        42 -> "Magic: $y"
+        else -> "Not magic: $y"
+    }
+}

compiler/testData/diagnostics/tests/when/withSubjectVariable/shadowingOtherVariable.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(): kotlin.Any
+public fun test(/*0*/ y: kotlin.Any): kotlin.Unit

compiler/testData/diagnostics/tests/when/withSubjectVariable/unsupportedFeature.kt

@@ -0,0 +1,16 @@
+// !LANGUAGE: -VariableDeclarationInWhenSubject
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+fun foo(): Any = 42
+
+fun test(x: Any) {
+    // NB check that we still resolve 'y', even though current language version doesn' support variable declaration in when subject
+
+    val z1 = when (<!UNSUPPORTED_FEATURE!>val y = foo()<!>) {
+        42 -> "Magic: $y, $x"
+        else -> {
+            "Not magic: $y, $x"
+        }
+    }
+    val z2 = "Anyway, it was $<!UNRESOLVED_REFERENCE!>y<!>"
+}

compiler/testData/diagnostics/tests/when/withSubjectVariable/unsupportedFeature.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(): kotlin.Any
+public fun test(/*0*/ x: kotlin.Any): kotlin.Unit