psi2ir: Consistently use type unit for statements

These changes allow us to accurately distinguish between statements and
expressions in the IR.

This also fixes the types of non-exhaustive conditional statements.

compiler/testData/ir/irCfg/when/whenReturn.txt

@@ -2,10 +2,10 @@
 // FUN: toString
 BB 0
 CONTENT
-      1 FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String 
+      1 FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String
       2 GET_VAR 'grade: kotlin.String declared in <root>.toString' type=kotlin.String origin=null
-      3 VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.String [val] 
-      4 WHEN type=kotlin.Nothing origin=WHEN
+      3 VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.String [val]
+      4 WHEN type=kotlin.Unit origin=WHEN
       5 GET_VAR 'val tmp0_subject: kotlin.String [val] declared in <root>.toString' type=kotlin.String origin=null
       6 CONST String type=kotlin.String value="A"
 OUTGOING -> BB 1, 5
@@ -47,7 +47,7 @@ CONTENT
       1 CONST String type=kotlin.String value="Excellent"
       2 RETURN type=kotlin.Nothing from='public final fun toString (grade: kotlin.String): kotlin.String declared in <root>'
 OUTGOING -> NONE
-    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String 
+    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String
 BB 6
 INCOMING <- BB 1
     CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
@@ -55,7 +55,7 @@ CONTENT
       1 CONST String type=kotlin.String value="Good"
       2 RETURN type=kotlin.Nothing from='public final fun toString (grade: kotlin.String): kotlin.String declared in <root>'
 OUTGOING -> NONE
-    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String 
+    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String
 BB 7
 INCOMING <- BB 2
     CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
@@ -63,7 +63,7 @@ CONTENT
       1 CONST String type=kotlin.String value="Mediocre"
       2 RETURN type=kotlin.Nothing from='public final fun toString (grade: kotlin.String): kotlin.String declared in <root>'
 OUTGOING -> NONE
-    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String 
+    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String
 BB 8
 INCOMING <- BB 3
     CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
@@ -71,7 +71,7 @@ CONTENT
       1 CONST String type=kotlin.String value="Fair"
       2 RETURN type=kotlin.Nothing from='public final fun toString (grade: kotlin.String): kotlin.String declared in <root>'
 OUTGOING -> NONE
-    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String 
+    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String
 BB 9
 INCOMING <- BB 4
     CONST Boolean type=kotlin.Boolean value=true
@@ -79,7 +79,7 @@ CONTENT
       1 CONST String type=kotlin.String value="Failure"
       2 RETURN type=kotlin.Nothing from='public final fun toString (grade: kotlin.String): kotlin.String declared in <root>'
 OUTGOING -> NONE
-    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String 
+    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String
 BB 10
 INCOMING <- BB 4
     CONST Boolean type=kotlin.Boolean value=true
@@ -87,7 +87,7 @@ CONTENT
       1 CONST String type=kotlin.String value="???"
       2 RETURN type=kotlin.Nothing from='public final fun toString (grade: kotlin.String): kotlin.String declared in <root>'
 OUTGOING -> NONE
-    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String 
+    Function exit: FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String
 
 // END FUN: toString
 

compiler/testData/ir/irText/declarations/parameters/useNextParamInLambda.txt

@@ -23,15 +23,15 @@ FILE fqName:<root> fileName:/useNextParamInLambda.kt
     BLOCK_BODY
       VAR name:result type:kotlin.String [var]
         CONST String type=kotlin.String value="fail"
-      TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
-        TRY type=kotlin.Any
-          try: BLOCK type=kotlin.String origin=null
+      TRY type=kotlin.Unit
+        try: BLOCK type=kotlin.Unit origin=null
+          TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
             CALL 'public final fun f (f1: kotlin.Function0<kotlin.String>, f2: kotlin.Function0<kotlin.String>): kotlin.String declared in <root>' type=kotlin.String origin=null
-          CATCH parameter=val e: java.lang.Exception{ kotlin.Exception } [val] declared in <root>.box
-            VAR CATCH_PARAMETER name:e type:java.lang.Exception{ kotlin.Exception } [val]
-            BLOCK type=kotlin.Unit origin=null
-              SET_VAR 'var result: kotlin.String [var] declared in <root>.box' type=kotlin.Unit origin=EQ
-                CONST String type=kotlin.String value="OK"
+        CATCH parameter=val e: java.lang.Exception{ kotlin.Exception } [val] declared in <root>.box
+          VAR CATCH_PARAMETER name:e type:java.lang.Exception{ kotlin.Exception } [val]
+          BLOCK type=kotlin.Unit origin=null
+            SET_VAR 'var result: kotlin.String [var] declared in <root>.box' type=kotlin.Unit origin=EQ
+              CONST String type=kotlin.String value="OK"
       RETURN type=kotlin.Nothing from='public final fun box (): kotlin.String declared in <root>'
         CALL 'public final fun plus (other: kotlin.Any?): kotlin.String declared in kotlin.String' type=kotlin.String origin=PLUS
           $this: CALL 'public final fun f (f1: kotlin.Function0<kotlin.String>, f2: kotlin.Function0<kotlin.String>): kotlin.String declared in <root>' type=kotlin.String origin=null

compiler/testData/ir/irText/expressions/breakContinueInWhen.txt

@@ -23,8 +23,8 @@ FILE fqName:<root> fileName:/breakContinueInWhen.kt
             VAR FOR_LOOP_VARIABLE name:x type:kotlin.Int [val]
               CALL 'public final fun next (): kotlin.Int declared in kotlin.collections.IntIterator' type=kotlin.Int origin=FOR_LOOP_NEXT
                 $this: GET_VAR 'val tmp0_iterator: kotlin.collections.IntIterator [val] declared in <root>.testBreakFor' type=kotlin.collections.IntIterator origin=null
-            BLOCK type=kotlin.Nothing origin=null
-              WHEN type=kotlin.Nothing origin=WHEN
+            BLOCK type=kotlin.Unit origin=null
+              WHEN type=kotlin.Unit origin=WHEN
                 BRANCH
                   if: CALL 'public final fun greater (arg0: kotlin.Int, arg1: kotlin.Int): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=GT
                     arg0: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testBreakFor' type=kotlin.Int origin=null
@@ -39,7 +39,7 @@ FILE fqName:<root> fileName:/breakContinueInWhen.kt
           arg0: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testBreakWhile' type=kotlin.Int origin=null
           arg1: CONST Int type=kotlin.Int value=10
         body: BLOCK type=kotlin.Unit origin=null
-          WHEN type=kotlin.Nothing origin=WHEN
+          WHEN type=kotlin.Unit origin=WHEN
             BRANCH
               if: CALL 'public final fun greater (arg0: kotlin.Int, arg1: kotlin.Int): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=GT
                 arg0: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testBreakWhile' type=kotlin.Int origin=null
@@ -52,7 +52,7 @@ FILE fqName:<root> fileName:/breakContinueInWhen.kt
       BLOCK type=kotlin.Unit origin=null
         DO_WHILE label=null origin=DO_WHILE_LOOP
           body: COMPOSITE type=kotlin.Unit origin=null
-            WHEN type=kotlin.Nothing origin=WHEN
+            WHEN type=kotlin.Unit origin=WHEN
               BRANCH
                 if: CALL 'public final fun greater (arg0: kotlin.Int, arg1: kotlin.Int): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=GT
                   arg0: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testBreakDoWhile' type=kotlin.Int origin=null
@@ -85,8 +85,8 @@ FILE fqName:<root> fileName:/breakContinueInWhen.kt
             VAR FOR_LOOP_VARIABLE name:x type:kotlin.Int [val]
               CALL 'public final fun next (): kotlin.Int declared in kotlin.collections.IntIterator' type=kotlin.Int origin=FOR_LOOP_NEXT
                 $this: GET_VAR 'val tmp0_iterator: kotlin.collections.IntIterator [val] declared in <root>.testContinueFor' type=kotlin.collections.IntIterator origin=null
-            BLOCK type=kotlin.Nothing origin=null
-              WHEN type=kotlin.Nothing origin=WHEN
+            BLOCK type=kotlin.Unit origin=null
+              WHEN type=kotlin.Unit origin=WHEN
                 BRANCH
                   if: CALL 'public final fun greater (arg0: kotlin.Int, arg1: kotlin.Int): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=GT
                     arg0: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testContinueFor' type=kotlin.Int origin=null
@@ -101,7 +101,7 @@ FILE fqName:<root> fileName:/breakContinueInWhen.kt
           arg0: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testContinueWhile' type=kotlin.Int origin=null
           arg1: CONST Int type=kotlin.Int value=10
         body: BLOCK type=kotlin.Unit origin=null
-          WHEN type=kotlin.Nothing origin=WHEN
+          WHEN type=kotlin.Unit origin=WHEN
             BRANCH
               if: CALL 'public final fun greater (arg0: kotlin.Int, arg1: kotlin.Int): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=GT
                 arg0: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testContinueWhile' type=kotlin.Int origin=null
@@ -122,7 +122,7 @@ FILE fqName:<root> fileName:/breakContinueInWhen.kt
                   CALL 'public final fun inc (): kotlin.Int declared in kotlin.Int' type=kotlin.Int origin=PREFIX_INCR
                     $this: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testContinueDoWhile' type=kotlin.Int origin=PREFIX_INCR
                 GET_VAR 'var k: kotlin.Int [var] declared in <root>.testContinueDoWhile' type=kotlin.Int origin=PREFIX_INCR
-            WHEN type=kotlin.Nothing origin=WHEN
+            WHEN type=kotlin.Unit origin=WHEN
               BRANCH
                 if: CALL 'public final fun greater (arg0: kotlin.Int, arg1: kotlin.Int): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=GT
                   arg0: GET_VAR 'var k: kotlin.Int [var] declared in <root>.testContinueDoWhile' type=kotlin.Int origin=null

compiler/testData/ir/irText/expressions/catchParameterAccess.txt

@@ -9,6 +9,6 @@ FILE fqName:<root> fileName:/catchParameterAccess.kt
               $this: GET_VAR 'f: kotlin.Function0<kotlin.Unit> declared in <root>.test' type=kotlin.Function0<kotlin.Unit> origin=VARIABLE_AS_FUNCTION
           CATCH parameter=val e: java.lang.Exception{ kotlin.Exception } [val] declared in <root>.test
             VAR CATCH_PARAMETER name:e type:java.lang.Exception{ kotlin.Exception } [val]
-            BLOCK type=kotlin.Nothing origin=null
+            BLOCK type=kotlin.Unit origin=null
               THROW type=kotlin.Nothing
                 GET_VAR 'val e: java.lang.Exception{ kotlin.Exception } [val] declared in <root>.test' type=java.lang.Exception{ kotlin.Exception } origin=null

compiler/testData/ir/irText/expressions/forWithBreakContinue.txt

@@ -13,7 +13,7 @@ FILE fqName:<root> fileName:/forWithBreakContinue.kt
             VAR FOR_LOOP_VARIABLE name:s type:kotlin.String [val]
               CALL 'public abstract fun next (): T of kotlin.collections.Iterator declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
                 $this: GET_VAR 'val tmp0_iterator: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.testForBreak1' type=kotlin.collections.Iterator<kotlin.String> origin=null
-            BLOCK type=kotlin.Nothing origin=null
+            BLOCK type=kotlin.Unit origin=null
               BREAK label=null loop.label=null
   FUN name:testForBreak2 visibility:public modality:FINAL <> (ss:kotlin.collections.List<kotlin.String>) returnType:kotlin.Unit
     VALUE_PARAMETER name:ss index:0 type:kotlin.collections.List<kotlin.String>
@@ -29,7 +29,7 @@ FILE fqName:<root> fileName:/forWithBreakContinue.kt
             VAR FOR_LOOP_VARIABLE name:s1 type:kotlin.String [val]
               CALL 'public abstract fun next (): T of kotlin.collections.Iterator declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
                 $this: GET_VAR 'val tmp0_iterator: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.testForBreak2' type=kotlin.collections.Iterator<kotlin.String> origin=null
-            BLOCK type=kotlin.Nothing origin=null
+            BLOCK type=kotlin.Unit origin=null
               BLOCK type=kotlin.Unit origin=FOR_LOOP
                 VAR FOR_LOOP_ITERATOR name:tmp1_iterator type:kotlin.collections.Iterator<kotlin.String> [val]
                   CALL 'public abstract fun iterator (): kotlin.collections.Iterator<E of kotlin.collections.List> declared in kotlin.collections.List' type=kotlin.collections.Iterator<kotlin.String> origin=FOR_LOOP_ITERATOR
@@ -41,7 +41,7 @@ FILE fqName:<root> fileName:/forWithBreakContinue.kt
                     VAR FOR_LOOP_VARIABLE name:s2 type:kotlin.String [val]
                       CALL 'public abstract fun next (): T of kotlin.collections.Iterator declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
                         $this: GET_VAR 'val tmp1_iterator: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.testForBreak2' type=kotlin.collections.Iterator<kotlin.String> origin=null
-                    BLOCK type=kotlin.Nothing origin=null
+                    BLOCK type=kotlin.Unit origin=null
                       BREAK label=OUTER loop.label=OUTER
                       BREAK label=INNER loop.label=INNER
                       BREAK label=null loop.label=INNER
@@ -60,7 +60,7 @@ FILE fqName:<root> fileName:/forWithBreakContinue.kt
             VAR FOR_LOOP_VARIABLE name:s type:kotlin.String [val]
               CALL 'public abstract fun next (): T of kotlin.collections.Iterator declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
                 $this: GET_VAR 'val tmp0_iterator: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.testForContinue1' type=kotlin.collections.Iterator<kotlin.String> origin=null
-            BLOCK type=kotlin.Nothing origin=null
+            BLOCK type=kotlin.Unit origin=null
               CONTINUE label=null loop.label=null
   FUN name:testForContinue2 visibility:public modality:FINAL <> (ss:kotlin.collections.List<kotlin.String>) returnType:kotlin.Unit
     VALUE_PARAMETER name:ss index:0 type:kotlin.collections.List<kotlin.String>
@@ -76,7 +76,7 @@ FILE fqName:<root> fileName:/forWithBreakContinue.kt
             VAR FOR_LOOP_VARIABLE name:s1 type:kotlin.String [val]
               CALL 'public abstract fun next (): T of kotlin.collections.Iterator declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
                 $this: GET_VAR 'val tmp0_iterator: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.testForContinue2' type=kotlin.collections.Iterator<kotlin.String> origin=null
-            BLOCK type=kotlin.Nothing origin=null
+            BLOCK type=kotlin.Unit origin=null
               BLOCK type=kotlin.Unit origin=FOR_LOOP
                 VAR FOR_LOOP_ITERATOR name:tmp1_iterator type:kotlin.collections.Iterator<kotlin.String> [val]
                   CALL 'public abstract fun iterator (): kotlin.collections.Iterator<E of kotlin.collections.List> declared in kotlin.collections.List' type=kotlin.collections.Iterator<kotlin.String> origin=FOR_LOOP_ITERATOR
@@ -88,7 +88,7 @@ FILE fqName:<root> fileName:/forWithBreakContinue.kt
                     VAR FOR_LOOP_VARIABLE name:s2 type:kotlin.String [val]
                       CALL 'public abstract fun next (): T of kotlin.collections.Iterator declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
                         $this: GET_VAR 'val tmp1_iterator: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.testForContinue2' type=kotlin.collections.Iterator<kotlin.String> origin=null
-                    BLOCK type=kotlin.Nothing origin=null
+                    BLOCK type=kotlin.Unit origin=null
                       CONTINUE label=OUTER loop.label=OUTER
                       CONTINUE label=INNER loop.label=INNER
                       CONTINUE label=null loop.label=INNER

compiler/testData/ir/irText/expressions/ifElseIf.txt

@@ -36,22 +36,22 @@ FILE fqName:<root> fileName:/ifElseIf.kt
   FUN name:testEmptyBranches2 visibility:public modality:FINAL <> (flag:kotlin.Boolean) returnType:kotlin.Unit
     VALUE_PARAMETER name:flag index:0 type:kotlin.Boolean
     BLOCK_BODY
-      TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
-        WHEN type=kotlin.Any origin=IF
-          BRANCH
-            if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches2' type=kotlin.Boolean origin=null
-            then: BLOCK type=kotlin.Unit origin=null
-          BRANCH
-            if: CONST Boolean type=kotlin.Boolean value=true
-            then: CONST Boolean type=kotlin.Boolean value=true
-      TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
-        WHEN type=kotlin.Any origin=IF
-          BRANCH
-            if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches2' type=kotlin.Boolean origin=null
-            then: CONST Boolean type=kotlin.Boolean value=true
-          BRANCH
-            if: CONST Boolean type=kotlin.Boolean value=true
-            then: BLOCK type=kotlin.Unit origin=null
+      WHEN type=kotlin.Unit origin=IF
+        BRANCH
+          if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches2' type=kotlin.Boolean origin=null
+          then: BLOCK type=kotlin.Unit origin=null
+        BRANCH
+          if: CONST Boolean type=kotlin.Boolean value=true
+          then: TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+            CONST Boolean type=kotlin.Boolean value=true
+      WHEN type=kotlin.Unit origin=IF
+        BRANCH
+          if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches2' type=kotlin.Boolean origin=null
+          then: TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+            CONST Boolean type=kotlin.Boolean value=true
+        BRANCH
+          if: CONST Boolean type=kotlin.Boolean value=true
+          then: BLOCK type=kotlin.Unit origin=null
   FUN name:testEmptyBranches3 visibility:public modality:FINAL <> (flag:kotlin.Boolean) returnType:kotlin.Unit
     VALUE_PARAMETER name:flag index:0 type:kotlin.Boolean
     BLOCK_BODY

compiler/testData/ir/irText/expressions/throw.txt

@@ -10,7 +10,7 @@ FILE fqName:<root> fileName:/throw.kt
         BRANCH
           if: TYPE_OP type=kotlin.Boolean origin=INSTANCEOF typeOperand=kotlin.Throwable
             GET_VAR 'a: kotlin.Any declared in <root>.testImplicitCast' type=kotlin.Any origin=null
-          then: BLOCK type=kotlin.Nothing origin=null
+          then: BLOCK type=kotlin.Unit origin=null
             THROW type=kotlin.Nothing
               TYPE_OP type=kotlin.Throwable origin=IMPLICIT_CAST typeOperand=kotlin.Throwable
                 GET_VAR 'a: kotlin.Any declared in <root>.testImplicitCast' type=kotlin.Any origin=null

compiler/testData/ir/irText/expressions/tryCatch.txt

@@ -22,7 +22,7 @@ FILE fqName:<root> fileName:/tryCatch.kt
             BLOCK type=kotlin.Int origin=null
               CALL 'public final fun println (): kotlin.Unit [inline] declared in kotlin.io' type=kotlin.Unit origin=null
               CONST Int type=kotlin.Int value=24
-          finally: TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
-            BLOCK type=kotlin.Int origin=null
-              CALL 'public final fun println (): kotlin.Unit [inline] declared in kotlin.io' type=kotlin.Unit origin=null
+          finally: BLOCK type=kotlin.Unit origin=null
+            CALL 'public final fun println (): kotlin.Unit [inline] declared in kotlin.io' type=kotlin.Unit origin=null
+            TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
               CONST Int type=kotlin.Int value=555

compiler/testData/ir/irText/expressions/whenReturn.txt

@@ -2,10 +2,10 @@ FILE fqName:<root> fileName:/whenReturn.kt
   FUN name:toString visibility:public modality:FINAL <> (grade:kotlin.String) returnType:kotlin.String
     VALUE_PARAMETER name:grade index:0 type:kotlin.String
     BLOCK_BODY
-      BLOCK type=kotlin.Nothing origin=WHEN
+      BLOCK type=kotlin.Unit origin=WHEN
         VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.String [val]
           GET_VAR 'grade: kotlin.String declared in <root>.toString' type=kotlin.String origin=null
-        WHEN type=kotlin.Nothing origin=WHEN
+        WHEN type=kotlin.Unit origin=WHEN
           BRANCH
             if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
               arg0: GET_VAR 'val tmp0_subject: kotlin.String [val] declared in <root>.toString' type=kotlin.String origin=null

compiler/testData/ir/irText/expressions/whenReturnUnit.txt

@@ -10,10 +10,10 @@ FILE fqName:<root> fileName:/whenReturnUnit.kt
           block: FUN_EXPR type=kotlin.Function0<kotlin.Unit> origin=LAMBDA
             FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Unit
               BLOCK_BODY
-                BLOCK type=kotlin.Nothing origin=WHEN
+                BLOCK type=kotlin.Unit origin=WHEN
                   VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.Int [val]
                     GET_VAR 'x: kotlin.Int declared in <root>.branch' type=kotlin.Int origin=null
-                  WHEN type=kotlin.Nothing origin=WHEN
+                  WHEN type=kotlin.Unit origin=WHEN
                     BRANCH
                       if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                         arg0: GET_VAR 'val tmp0_subject: kotlin.Int [val] declared in <root>.branch.<anonymous>' type=kotlin.Int origin=null

compiler/testData/ir/irText/expressions/whenUnusedExpression.txt

@@ -3,23 +3,25 @@ FILE fqName:<root> fileName:/whenUnusedExpression.kt
     VALUE_PARAMETER name:b index:0 type:kotlin.Boolean
     VALUE_PARAMETER name:i index:1 type:kotlin.Int
     BLOCK_BODY
-      TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
-        WHEN type=kotlin.Int? origin=IF
-          BRANCH
-            if: GET_VAR 'b: kotlin.Boolean declared in <root>.test' type=kotlin.Boolean origin=null
-            then: BLOCK type=kotlin.Int? origin=null
-              BLOCK type=kotlin.Int? origin=WHEN
-                VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.Int [val]
-                  GET_VAR 'i: kotlin.Int declared in <root>.test' type=kotlin.Int origin=null
-                WHEN type=kotlin.Int? origin=WHEN
-                  BRANCH
-                    if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
-                      arg0: GET_VAR 'val tmp0_subject: kotlin.Int [val] declared in <root>.test' type=kotlin.Int origin=null
-                      arg1: CONST Int type=kotlin.Int value=0
-                    then: CONST Int type=kotlin.Int value=1
-                  BRANCH
-                    if: CONST Boolean type=kotlin.Boolean value=true
-                    then: CONST Null type=kotlin.Nothing? value=null
-          BRANCH
-            if: CONST Boolean type=kotlin.Boolean value=true
-            then: CONST Null type=kotlin.Nothing? value=null
+      WHEN type=kotlin.Unit origin=IF
+        BRANCH
+          if: GET_VAR 'b: kotlin.Boolean declared in <root>.test' type=kotlin.Boolean origin=null
+          then: BLOCK type=kotlin.Unit origin=null
+            BLOCK type=kotlin.Unit origin=WHEN
+              VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.Int [val]
+                GET_VAR 'i: kotlin.Int declared in <root>.test' type=kotlin.Int origin=null
+              WHEN type=kotlin.Unit origin=WHEN
+                BRANCH
+                  if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
+                    arg0: GET_VAR 'val tmp0_subject: kotlin.Int [val] declared in <root>.test' type=kotlin.Int origin=null
+                    arg1: CONST Int type=kotlin.Int value=0
+                  then: TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+                    CONST Int type=kotlin.Int value=1
+                BRANCH
+                  if: CONST Boolean type=kotlin.Boolean value=true
+                  then: TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+                    CONST Null type=kotlin.Nothing? value=null
+        BRANCH
+          if: CONST Boolean type=kotlin.Boolean value=true
+          then: TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+            CONST Null type=kotlin.Nothing? value=null

compiler/testData/ir/irText/regressions/kt24114.txt

@@ -12,19 +12,19 @@ FILE fqName:<root> fileName:/kt24114.kt
       WHILE label=null origin=WHILE_LOOP
         condition: CONST Boolean type=kotlin.Boolean value=true
         body: BLOCK type=kotlin.Unit origin=null
-          BLOCK type=kotlin.Nothing origin=WHEN
+          BLOCK type=kotlin.Unit origin=WHEN
             VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.Int [val]
               CALL 'public final fun one (): kotlin.Int declared in <root>' type=kotlin.Int origin=null
-            WHEN type=kotlin.Nothing origin=WHEN
+            WHEN type=kotlin.Unit origin=WHEN
               BRANCH
                 if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                   arg0: GET_VAR 'val tmp0_subject: kotlin.Int [val] declared in <root>.test1' type=kotlin.Int origin=null
                   arg1: CONST Int type=kotlin.Int value=1
-                then: BLOCK type=kotlin.Nothing origin=null
-                  BLOCK type=kotlin.Nothing origin=WHEN
+                then: BLOCK type=kotlin.Unit origin=null
+                  BLOCK type=kotlin.Unit origin=WHEN
                     VAR IR_TEMPORARY_VARIABLE name:tmp1_subject type:kotlin.Int [val]
                       CALL 'public final fun two (): kotlin.Int declared in <root>' type=kotlin.Int origin=null
-                    WHEN type=kotlin.Nothing origin=WHEN
+                    WHEN type=kotlin.Unit origin=WHEN
                       BRANCH
                         if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                           arg0: GET_VAR 'val tmp1_subject: kotlin.Int [val] declared in <root>.test1' type=kotlin.Int origin=null
@@ -40,18 +40,18 @@ FILE fqName:<root> fileName:/kt24114.kt
       WHILE label=null origin=WHILE_LOOP
         condition: CONST Boolean type=kotlin.Boolean value=true
         body: BLOCK type=kotlin.Unit origin=null
-          BLOCK type=kotlin.Nothing origin=WHEN
+          BLOCK type=kotlin.Unit origin=WHEN
             VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.Int [val]
               CALL 'public final fun one (): kotlin.Int declared in <root>' type=kotlin.Int origin=null
-            WHEN type=kotlin.Nothing origin=WHEN
+            WHEN type=kotlin.Unit origin=WHEN
               BRANCH
                 if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                   arg0: GET_VAR 'val tmp0_subject: kotlin.Int [val] declared in <root>.test2' type=kotlin.Int origin=null
                   arg1: CONST Int type=kotlin.Int value=1
-                then: BLOCK type=kotlin.Nothing origin=WHEN
+                then: BLOCK type=kotlin.Unit origin=WHEN
                   VAR IR_TEMPORARY_VARIABLE name:tmp1_subject type:kotlin.Int [val]
                     CALL 'public final fun two (): kotlin.Int declared in <root>' type=kotlin.Int origin=null
-                  WHEN type=kotlin.Nothing origin=WHEN
+                  WHEN type=kotlin.Unit origin=WHEN
                     BRANCH
                       if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                         arg0: GET_VAR 'val tmp1_subject: kotlin.Int [val] declared in <root>.test2' type=kotlin.Int origin=null