K2: Fix false-negative RETURN_TYPE_MISMATCH

^KT-53987 Fixed
^KT-55932 Fixed

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

@@ -152,7 +152,7 @@ fun illegalIfBlock(): Boolean {
     else { return <!RETURN_TYPE_MISMATCH!>1<!> }
 }
 fun illegalReturnIf(): Char {
-    return if (1 < 2) 'a' else { 1 }
+    return <!RETURN_TYPE_MISMATCH!>if (1 < 2) 'a' else { 1 }<!>
 }
 
 fun returnNothing(): Nothing {

compiler/testData/diagnostics/tests/controlStructures/ifElseIntersection.fir.kt

@@ -24,11 +24,11 @@ fun <T> bind2(r: Option<T>): Option<T> {
 }
 
 fun <T, R> bind3(r: Option<T>): Option<T> {
-    return if (r is Some) {
+    return <!RETURN_TYPE_MISMATCH!>if (r is Some) {
         // Diagnoses an error correctly
         if (true) None<R>() else r
     }
-    else r
+    else r<!>
 }
 
 fun <T> bindWhen(r: Option<T>): Option<T> {

compiler/testData/diagnostics/tests/controlStructures/incorrectElvis.fir.kt

@@ -0,0 +1,4 @@
+// SKIP_TXT
+// ISSUE: KT-55932
+
+fun test(x: String?): Int = <!RETURN_TYPE_MISMATCH!>x?.length ?: "smth"<!>

compiler/testData/diagnostics/tests/controlStructures/incorrectElvis.kt

@@ -0,0 +1,4 @@
+// SKIP_TXT
+// ISSUE: KT-55932
+
+fun test(x: String?): Int = <!TYPE_MISMATCH!>x?.length ?: "smth"<!>

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ObjectExpression.fir.kt

@@ -6,6 +6,6 @@ fun foo() {
 
     val a = object {
         fun baz() = bar(if (x == null) 0 else x)
-        fun quux(): Int = if (x == null) x else x
+        fun quux(): Int = <!RETURN_TYPE_MISMATCH!>if (x == null) x else x<!>
     }
 }

compiler/testData/diagnostics/tests/delegatedProperty/inference/genericMethodInGenericClass.fir.kt

@@ -24,4 +24,4 @@ class C<R>() {
 }
 
 var c1: Int by C()
-var c2: Int by <!DELEGATE_SPECIAL_FUNCTION_NONE_APPLICABLE!>C<Number>()<!>
+var c2: Int by <!DELEGATE_SPECIAL_FUNCTION_RETURN_TYPE_MISMATCH!>C<Number>()<!>

compiler/testData/diagnostics/tests/delegatedProperty/provideDelegate/noOperatorModifierOnProvideDelegate.fir.kt

@@ -0,0 +1,16 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+import kotlin.reflect.KProperty
+
+class StringDelegate(val s: String) {
+    operator fun getValue(a: Any?, p: KProperty<*>): Int = 42
+}
+
+// NB no operator
+fun String.provideDelegate(a: Any?, p: KProperty<*>) = StringDelegate(this)
+
+operator fun String.getValue(a: Any?, p: KProperty<*>) = this
+
+val test1: String by "OK"
+val test2: Int by <!DELEGATE_SPECIAL_FUNCTION_RETURN_TYPE_MISMATCH!>"OK"<!>
+val test3 by "OK"

compiler/testData/diagnostics/tests/delegatedProperty/provideDelegate/noOperatorModifierOnProvideDelegate.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 
 import kotlin.reflect.KProperty

compiler/testData/diagnostics/tests/delegatedProperty/typeMismatchForGetReturnType.fir.kt

@@ -0,0 +1,11 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+import kotlin.reflect.KProperty
+
+val c: Int by <!DELEGATE_SPECIAL_FUNCTION_RETURN_TYPE_MISMATCH!>Delegate()<!>
+
+class Delegate {
+  operator fun getValue(t: Any?, p: KProperty<*>): String {
+    return ""
+  }
+}

compiler/testData/diagnostics/tests/delegatedProperty/typeMismatchForGetReturnType.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 
 import kotlin.reflect.KProperty

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/kt2146.fir.kt

@@ -9,46 +9,46 @@ fun f1(s: Int?): Int {
 }
 
 fun f2(s: Int?): Int {
-    return when (s) {
+    return <!RETURN_TYPE_MISMATCH!>when (s) {
         !is Int -> s
         else -> s
-    }
+    }<!>
 }
 
 fun f3(s: Int?): Int {
-    return when (s) {
+    return <!RETURN_TYPE_MISMATCH!>when (s) {
         is Int -> s
         else -> s
-    }
+    }<!>
 }
 
 fun f4(s: Int?): Int {
-    return when {
+    return <!RETURN_TYPE_MISMATCH!>when {
         s == 4 -> s
         s == null -> s
         else -> s
-    }
+    }<!>
 }
 
 fun f5(s: Int?): Int {
-    return when (s) {
+    return <!RETURN_TYPE_MISMATCH!>when (s) {
         s -> s
         s!! -> s
         s -> s
         else -> 0
-    }
+    }<!>
 }
 
 fun f6(s: Int?): Int {
-    return when {
+    return <!RETURN_TYPE_MISMATCH!>when {
         s is Int -> s
         else -> s
-    }
+    }<!>
 }
 
 fun f7(s: Int?): Int {
-    return when {
+    return <!RETURN_TYPE_MISMATCH!>when {
         s !is Int -> s
         else -> s
-    }
+    }<!>
 }

compiler/testData/diagnostics/tests/resolve/newLineLambda.fir.kt

@@ -99,13 +99,13 @@ fun testTwoLambdas() {
         {}
         <!MANY_LAMBDA_EXPRESSION_ARGUMENTS!>{}<!>
 
-        return if (true) {
+        return <!RETURN_TYPE_MISMATCH!>if (true) {
             twoLambdaArgs({})
             {}
             <!MANY_LAMBDA_EXPRESSION_ARGUMENTS!>{}<!>
         } else {
-            <!ARGUMENT_TYPE_MISMATCH!>{}<!>
-        }
+            {}
+        }<!>
     }
 }
 

compiler/testData/diagnostics/tests/smartCasts/publicVals/delegate.fir.kt

@@ -13,7 +13,7 @@ class Example {
 
     public fun foo(): String {
         // Smart cast is not possible if property is delegated
-        return if (p != null) p else ""
+        return <!RETURN_TYPE_MISMATCH!>if (p != null) p else ""<!>
     }
 
     public fun bar(): String {

compiler/testData/diagnostics/tests/typeParameters/implicitNothingInReturnPosition.fir.kt

@@ -39,7 +39,7 @@ class Context<T>
 fun <T> Any.decodeIn(typeFrom: Context<in T>): T = something()
 
 fun <T> Any?.decodeOut1(typeFrom: Context<out T>): T {
-    return this?.decodeIn(typeFrom) ?: kotlin.Unit
+    return <!RETURN_TYPE_MISMATCH!>this?.decodeIn(typeFrom) ?: kotlin.Unit<!>
 }
 
 fun <T> Any.decodeOut2(typeFrom: Context<out T>): T {