Introduce FirFunctionReturnTypeMismatchChecker

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

@@ -33,15 +33,15 @@ fun testReturnFromAnonFun() =
 
 fun testReturn1() =
         run {
-            return if (true) 42
-                   else println()
+            return <!RETURN_TYPE_MISMATCH!>if (true) 42
+                   else println()<!>
         }
 
 fun testReturn2() =
         run {
-            return if (true) 42
+            return <!RETURN_TYPE_MISMATCH!>if (true) 42
                    else if (true) 42
-                   else println()
+                   else println()<!>
         }
 
 fun testUsage1() =

compiler/testData/diagnostics/tests/controlStructures/kt10717.fir.kt

@@ -1,21 +1,21 @@
 // !DIAGNOSTICS: -UNUSED_EXPRESSION -UNREACHABLE_CODE -UNUSED_PARAMETER -RETURN_NOT_ALLOWED
 
 fun test1() = run {
-    return "OK"
+    return <!RETURN_TYPE_MISMATCH!>"OK"<!>
 }
 
 fun test2() = run {
     fun local(): String {
         return ""
     }
-    return ""
+    return <!RETURN_TYPE_MISMATCH!>""<!>
 }
 
 inline fun <T, R> Iterable<T>.map(transform: (T) -> R): List<R> = null!!
 fun test3(a: List<String>, b: List<Int>) = a.map {
-    if (it.length == 3) return null
-    if (it.length == 4) return ""
-    if (it.length == 4) return 5
+    if (it.length == 3) return <!RETURN_TYPE_MISMATCH!>null<!>
+    if (it.length == 4) return <!RETURN_TYPE_MISMATCH!>""<!>
+    if (it.length == 4) return <!RETURN_TYPE_MISMATCH!>5<!>
     if (it.length == 4) return b
     1
 }
@@ -24,14 +24,14 @@ fun test4() = run {
     fun test5() {
         return
 
-        return@test4
+        <!RETURN_TYPE_MISMATCH!>return@test4<!>
 
-        return return@test4
+        return <!RETURN_TYPE_MISMATCH!>return@test4<!>
 
-        return fun() { return; return@test4 "" }
+        return <!RETURN_TYPE_MISMATCH!>fun() { return; return@test4 <!RETURN_TYPE_MISMATCH!>""<!> }<!>
     }
 
-    return
+    <!RETURN_TYPE_MISMATCH!>return<!>
     3
 }
 
@@ -43,5 +43,5 @@ val foo: Int
     }
 
 fun test(): Int = run {
-    return ""
+    return <!RETURN_TYPE_MISMATCH!>""<!>
 }

compiler/testData/diagnostics/tests/controlStructures/kt4310.fir.kt

@@ -2,11 +2,11 @@
 package f
 
 fun test(a: Boolean, b: Boolean): Int {
-    return if(a) {
+    return <!RETURN_TYPE_MISMATCH!>if(a) {
         1
     } else {
         if (b) {
             3
         }
-    }
+    }<!>
 }

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

@@ -10,7 +10,7 @@ fun f() = object : ClassData {
 fun g() = object : ClassData {
     init {
         if (true) {
-            <!RETURN_NOT_ALLOWED!>return<!> 0
+            <!RETURN_NOT_ALLOWED!>return<!> <!RETURN_TYPE_MISMATCH!>0<!>
         }
     }
 

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

@@ -17,4 +17,4 @@ fun g() = object : ClassData {
     fun some(): Int {
         return 6
     }
-}
+}

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

@@ -6,15 +6,15 @@ fun foo() : Int {
         doSmth()
     }
     catch (e: Exception) {
-        return ""
+        return <!RETURN_TYPE_MISMATCH!>""<!>
     }
     finally {
-        return ""
+        return <!RETURN_TYPE_MISMATCH!>""<!>
     }
 }
 
 fun bar() : Int =
-    try {
+    <!RETURN_TYPE_MISMATCH!>try {
         doSmth()
     }
     catch (e: Exception) {
@@ -22,7 +22,7 @@ fun bar() : Int =
     }
     finally {
         ""
-    }
+    }<!>
 
 
 fun doSmth() {}

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

@@ -26,22 +26,22 @@ fun testResultOfLambda2() =
 
 fun testReturn1() =
         run {
-            return when {
+            return <!RETURN_TYPE_MISMATCH!>when {
                 true -> 42
                 else -> println()
-            }
+            }<!>
         }
 
 fun testReturn2() =
         run {
-            return when {
+            return <!RETURN_TYPE_MISMATCH!>when {
                 true -> 42
                 else ->
                     when {
                         true -> 42
                         else -> println()
                     }
-            }
+            }<!>
         }
 
 fun testUsage1() =