Local returns are only allowed with explicitly specified return types

This is a temporary limitation: otherwise type inference is having trouble to account for all the returned expressions.
 We will fix the inference and remove the limitation

compiler/testData/diagnostics/tests/FunctionReturnTypes.kt

@@ -6,10 +6,10 @@ fun unitEmptyReturn() : Unit {return}
 fun unitIntReturn() : Unit {return <!TYPE_MISMATCH!>1<!>}
 fun unitUnitReturn() : Unit {return Unit.VALUE}
 fun test1() : Any = {<!RETURN_NOT_ALLOWED, RETURN_TYPE_MISMATCH!>return<!>}
-fun test2() : Any = @a {return@a 1}
+fun test2() : Any = @a {<!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@a 1<!>}
 fun test3() : Any { <!RETURN_TYPE_MISMATCH!>return<!> }
 fun test4(): ()-> Unit = { <!RETURN_NOT_ALLOWED, RETURN_TYPE_MISMATCH!>return@test4<!> }
-fun test5(): Any = @{ return@ }
+fun test5(): Any = @{ <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@<!> }
 fun test6(): Any = {<!RETURN_NOT_ALLOWED!>return 1<!>}
 
 fun bbb() {

compiler/testData/diagnostics/tests/functionLiterals/return/LocalAndNonLocalReturnInLambda.kt

@@ -1,7 +1,7 @@
 fun test2(a: Int) {
     (run @f{
       if (a > 0) <!RETURN_NOT_ALLOWED!>return<!>
-      return@f 1
+      <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f 1<!>
     }): Int
 }
 

compiler/testData/diagnostics/tests/functionLiterals/return/LocalReturnExplicitLabelNoParens.kt

@@ -1,5 +1,5 @@
 fun test2() {
-    (run @f{return@f 1}): Int
+    (run @f{<!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f 1<!>}): Int
 }
 
 fun run<T>(f: () -> T): T { return f() }

compiler/testData/diagnostics/tests/functionLiterals/return/LocalReturnExplicitLabelParens.kt

@@ -1,10 +1,10 @@
 fun test() {
-    run(@f{return@f 1}): Int
+    run(@f{<!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f 1<!>}): Int
 }
 
 
 fun test1() {
-    run(@{return@ 1}): Int
+    run(@{<!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@ 1<!>}): Int
 }
 
 fun run<T>(f: () -> T): T { return f() }

compiler/testData/diagnostics/tests/functionLiterals/return/LocalReturnInNestedFunction.kt

@@ -4,7 +4,7 @@ fun test() {
         if (a > 0) return "2"
         return@local "3"
       }
-      return@f 1
+      <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f 1<!>
     }): Int
 }
 

compiler/testData/diagnostics/tests/functionLiterals/return/LocalReturnInNestedLambda.kt

@@ -1,9 +1,9 @@
 fun test() {
     (run @f{
       run @ff {
-        return@ff "2"
+        <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@ff "2"<!>
       }
-      return@f 1
+      <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f 1<!>
     }): Int
 }
 

compiler/testData/diagnostics/tests/functionLiterals/return/LocalReturnNoCoercionToUnit.kt

@@ -1,7 +1,7 @@
 fun test(a: Int) {
     run @f{
-      if (a > 0) return@f
-      else return@f 1
+      if (a > 0) <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f<!>
+      else <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f 1<!>
     }
 }
 

compiler/testData/diagnostics/tests/functionLiterals/return/LocalReturnUnit.kt

@@ -1,7 +1,7 @@
 fun test(a: Int) {
     (run @f{
-      if (a > 0) return@f
-      else return@f Unit.VALUE
+      if (a > 0) <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f<!>
+      else <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f Unit.VALUE<!>
     }): Unit
 }
 

compiler/testData/diagnostics/tests/functionLiterals/return/LocalReturnsWithExplicitReturnType.kt

@@ -0,0 +1,11 @@
+fun test(a: Int) {
+    run @f{ (): Int ->
+      if (a > 0) return@f <!TYPE_MISMATCH!>""<!>
+      return@f 1
+    }
+
+    run { (): Int -> <!TYPE_MISMATCH!>""<!> }
+    run { (): Int -> 1 }
+}
+
+fun run<T>(f: () -> T): T { return f() }

compiler/testData/diagnostics/tests/functionLiterals/return/MixedReturnsFromLambda.kt

@@ -5,7 +5,7 @@ trait C: A
 
 fun test(a: C, b: B) {
     (run @f{
-      if (a != b) return@f a
+      if (a != b) <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@f a<!>
       b
     }): A
 }

compiler/testData/diagnostics/tests/regressions/kt411.kt

@@ -5,7 +5,7 @@ package kt411
 fun f() {
     invoker(
     @{
-        return@ 11 // expects Function, but should expect Int
+        <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@ 11<!> // expects Function, but should expect Int
     }
     )
 }
@@ -21,7 +21,7 @@ fun t1() {
 fun t2() : String {
     val <!UNUSED_VARIABLE!>g<!> : ()-> Int = @{
         if (true) {
-            return@ 1
+            <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@ 1<!>
         }
         <!RETURN_NOT_ALLOWED!>return "s"<!>
     }
@@ -37,7 +37,7 @@ fun t3() : String {
         else {
             <!RETURN_NOT_ALLOWED!>return <!ERROR_COMPILE_TIME_VALUE!>2<!><!>
         }
-        return@ 0
+        <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@ 0<!>
     }
     )
     invoker(
@@ -55,7 +55,7 @@ fun t3() : String {
 
 fun t4() : Int {
     val <!UNUSED_VARIABLE!>h<!> :  ()-> String = @l{
-        return@l "a"
+        <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return@l "a"<!>
     }
     val <!UNUSED_VARIABLE!>g<!> :  ()-> String = @{ () : String ->
         return@ "a"
@@ -66,4 +66,4 @@ fun t4() : Int {
     }
 
     return 12
-}
+}