[FIR2IR] Coerce last operator in a loop to Unit

One of many fixes for https://youtrack.jetbrains.com/issue/KT-59781/K2-investigate-implicit-cast-generation-in-fir2ir-vs-psi2ir

Merge-request: KT-MR-12629
Merged-by: Vladimir Sukharev <Vladimir.Sukharev@jetbrains.com>

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrImplicitCastInserter.kt

@@ -157,7 +157,7 @@ class Fir2IrImplicitCastInserter(
     override fun visitDoWhileLoop(doWhileLoop: FirDoWhileLoop, data: IrElement): IrElement {
         val loop = data as IrDoWhileLoop
         (loop.body as? IrContainerExpression)?.let {
-            loop.body = it.insertImplicitCasts()
+            loop.body = it.insertImplicitCasts(coerceLastExpressionToUnit = true)
         }
         return data
     }
@@ -165,7 +165,7 @@ class Fir2IrImplicitCastInserter(
     override fun visitWhileLoop(whileLoop: FirWhileLoop, data: IrElement): IrElement {
         val loop = data as IrWhileLoop
         (loop.body as? IrContainerExpression)?.let {
-            loop.body = it.insertImplicitCasts()
+            loop.body = it.insertImplicitCasts(coerceLastExpressionToUnit = true)
         }
         return data
     }
@@ -339,7 +339,7 @@ class Fir2IrImplicitCastInserter(
             )
         }
 
-        private fun coerceToUnitIfNeeded(original: IrExpression, irBuiltIns: IrBuiltIns): IrExpression {
+        internal fun coerceToUnitIfNeeded(original: IrExpression, irBuiltIns: IrBuiltIns): IrExpression {
             val valueType = original.type
             return if (valueType.isUnit() || valueType.isNothing())
                 original

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt

@@ -45,6 +45,7 @@ import org.jetbrains.kotlin.ir.symbols.impl.IrValueParameterSymbolImpl
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.types.impl.IrErrorClassImpl
 import org.jetbrains.kotlin.ir.types.impl.IrErrorTypeImpl
+import org.jetbrains.kotlin.ir.util.coerceToUnit
 import org.jetbrains.kotlin.ir.util.constructors
 import org.jetbrains.kotlin.ir.util.defaultConstructor
 import org.jetbrains.kotlin.lexer.KtTokens
@@ -1295,7 +1296,10 @@ class Fir2IrVisitor(
                 loopMap[doWhileLoop] = this
                 label = doWhileLoop.label?.name
                 body = runUnless(doWhileLoop.block is FirEmptyExpressionBlock) {
-                    doWhileLoop.block.convertToIrExpressionOrBlock(origin)
+                    Fir2IrImplicitCastInserter.coerceToUnitIfNeeded(
+                        doWhileLoop.block.convertToIrExpressionOrBlock(origin),
+                        irBuiltIns
+                    )
                 }
                 condition = convertToIrExpression(doWhileLoop.condition)
                 loopMap.remove(doWhileLoop)
@@ -1360,7 +1364,10 @@ class Fir2IrVisitor(
                             )
                         }
                     } else {
-                        firLoopBody.convertToIrExpressionOrBlock(origin)
+                        Fir2IrImplicitCastInserter.coerceToUnitIfNeeded(
+                            firLoopBody.convertToIrExpressionOrBlock(origin),
+                            irBuiltIns
+                        )
                     }
                 }
                 loopMap.remove(whileLoop)

compiler/testData/codegen/box/fir/noSymbolForIntRangeIterator.fir.ir.txt

@@ -84,6 +84,7 @@ FILE fqName:<root> fileName:/noSymbolForIntRangeIterator.kt
                                   VAR FOR_LOOP_VARIABLE name:j 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 tmp_2: kotlin.collections.IntIterator declared in <root>.test.localFunc.<anonymous>' type=kotlin.collections.IntIterator origin=null
+                                  TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
                                     BLOCK type=java.lang.StringBuilder origin=null
                                       CALL 'public final fun appendLine (value: kotlin.String?): java.lang.StringBuilder declared in kotlin.text' type=java.lang.StringBuilder origin=null
                                         $receiver: GET_VAR '$this$buildString: java.lang.StringBuilder declared in <root>.test.localFunc.<anonymous>' type=java.lang.StringBuilder origin=null

compiler/testData/ir/irText/expressions/breakContinueInLoopHeader.fir.ir.txt

@@ -111,6 +111,7 @@ FILE fqName:<root> fileName:/breakContinueInLoopHeader.kt
           BLOCK type=kotlin.Unit origin=null
             DO_WHILE label=Inner origin=DO_WHILE_LOOP
               body: COMPOSITE type=kotlin.Unit origin=null
+                TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
                   BLOCK type=kotlin.Int origin=null
                     SET_VAR 'var j: kotlin.Int declared in <root>.test5' type=kotlin.Unit origin=PREFIX_INCR
                       CALL 'public final fun inc (): kotlin.Int declared in kotlin.Int' type=kotlin.Int origin=null

compiler/testData/ir/irText/expressions/breakContinueInLoopHeader.fir.kt.txt

@@ -69,7 +69,7 @@ fun test5() {
       { // BLOCK
         j = j.inc()
         j
-      }
+      } /*~> Unit */
       // }      while (when {
         greaterOrEqual(arg0 = j, arg1 = 3) -> false
         else -> break@Inner

compiler/testData/ir/irText/expressions/whileDoWhile.fir.ir.txt

@@ -11,7 +11,8 @@ FILE fqName:<root> fileName:/whileDoWhile.kt
         condition: CALL 'public final fun less (arg0: kotlin.Int, arg1: kotlin.Int): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=LT
           arg0: GET_VAR 'var x: kotlin.Int declared in <root>.test' type=kotlin.Int origin=null
           arg1: CONST Int type=kotlin.Int value=5
-        body: BLOCK type=kotlin.Int origin=POSTFIX_INCR
+        body: TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+          BLOCK type=kotlin.Int origin=POSTFIX_INCR
             VAR IR_TEMPORARY_VARIABLE name:tmp_0 type:kotlin.Int [val]
               GET_VAR 'var x: kotlin.Int declared in <root>.test' type=kotlin.Int origin=null
             SET_VAR 'var x: kotlin.Int declared in <root>.test' type=kotlin.Unit origin=POSTFIX_INCR
@@ -23,6 +24,7 @@ FILE fqName:<root> fileName:/whileDoWhile.kt
           arg0: GET_VAR 'var x: kotlin.Int declared in <root>.test' type=kotlin.Int origin=null
           arg1: CONST Int type=kotlin.Int value=10
         body: BLOCK type=kotlin.Unit origin=null
+          TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
             BLOCK type=kotlin.Int origin=POSTFIX_INCR
               VAR IR_TEMPORARY_VARIABLE name:tmp_1 type:kotlin.Int [val]
                 GET_VAR 'var x: kotlin.Int declared in <root>.test' type=kotlin.Int origin=null
@@ -43,7 +45,8 @@ FILE fqName:<root> fileName:/whileDoWhile.kt
             arg1: CONST Int type=kotlin.Int value=7
       BLOCK type=kotlin.Unit origin=null
         DO_WHILE label=null origin=DO_WHILE_LOOP
-          body: BLOCK type=kotlin.Int origin=POSTFIX_INCR
+          body: TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+            BLOCK type=kotlin.Int origin=POSTFIX_INCR
               VAR IR_TEMPORARY_VARIABLE name:tmp_2 type:kotlin.Int [val]
                 GET_VAR 'var x: kotlin.Int declared in <root>.test' type=kotlin.Int origin=null
               SET_VAR 'var x: kotlin.Int declared in <root>.test' type=kotlin.Unit origin=POSTFIX_INCR
@@ -56,6 +59,7 @@ FILE fqName:<root> fileName:/whileDoWhile.kt
       BLOCK type=kotlin.Unit origin=null
         DO_WHILE label=null origin=DO_WHILE_LOOP
           body: COMPOSITE type=kotlin.Unit origin=null
+            TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
               BLOCK type=kotlin.Int origin=POSTFIX_INCR
                 VAR IR_TEMPORARY_VARIABLE name:tmp_3 type:kotlin.Int [val]
                   GET_VAR 'var x: kotlin.Int declared in <root>.test' type=kotlin.Int origin=null

compiler/testData/ir/irText/expressions/whileDoWhile.fir.kt.txt

@@ -5,13 +5,13 @@ fun test() {
     val tmp_0: Int = x
     x = tmp_0.inc()
     tmp_0
-  }
+  } /*~> Unit */
   while (less(arg0 = x, arg1 = 10)) { // BLOCK
     { // BLOCK
       val tmp_1: Int = x
       x = tmp_1.inc()
       tmp_1
-    }
+    } /*~> Unit */
   }
   { // BLOCK
     do    while (less(arg0 = x, arg1 = 0))
@@ -25,7 +25,7 @@ fun test() {
       val tmp_2: Int = x
       x = tmp_2.inc()
       tmp_2
-    }    while (less(arg0 = x, arg1 = 15))
+    } /*~> Unit */    while (less(arg0 = x, arg1 = 15))
   }
   { // BLOCK
     do// COMPOSITE {
@@ -33,7 +33,7 @@ fun test() {
       val tmp_3: Int = x
       x = tmp_3.inc()
       tmp_3
-    }
+    } /*~> Unit */
     // }    while (less(arg0 = x, arg1 = 20))
   }
 }

compiler/testData/ir/irText/firProblems/ArrayMap.fir.ir.txt

@@ -545,6 +545,7 @@ FILE fqName:<root> fileName:/ArrayMap.kt
                   BLOCK type=kotlin.Unit origin=null
                     DO_WHILE label=null origin=DO_WHILE_LOOP
                       body: COMPOSITE type=kotlin.Unit origin=null
+                        TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
                           BLOCK type=kotlin.Int origin=POSTFIX_INCR
                             VAR IR_TEMPORARY_VARIABLE name:tmp_1 type:kotlin.Int [val]
                               CALL 'private final fun <get-index> (): kotlin.Int declared in <root>.ArrayMapImpl.iterator.<no name provided>' type=kotlin.Int origin=GET_PROPERTY

compiler/testData/ir/irText/firProblems/ArrayMap.fir.kt.txt

@@ -235,7 +235,7 @@ internal class ArrayMapImpl<T : Any> : ArrayMap<T> {
               val tmp_1: Int = <this>.<get-index>()
               <this>.<set-index>(<set-?> = tmp_1.inc())
               tmp_1
-            }
+            } /*~> Unit */
             // }            while (when {
               less(arg0 = <this>.<get-index>(), arg1 = <this>.<get-data>().<get-size>()) -> EQEQ(arg0 = <this>.<get-data>().get(index = <this>.<get-index>()), arg1 = null)
               else -> false

compiler/testData/ir/irText/firProblems/DeepCopyIrTree.fir.ir.txt

@@ -187,6 +187,7 @@ FILE fqName:<root> fileName:/DeepCopyIrTree.kt
                       VAR name:otherTypeParameter type:<root>.IrTypeParameter [val]
                         CALL 'public final fun component2 (): B of kotlin.Pair declared in kotlin.Pair' type=<root>.IrTypeParameter origin=COMPONENT_N(index=2)
                           $this: GET_VAR 'val tmp_1: kotlin.Pair<<root>.IrTypeParameter, <root>.IrTypeParameter> declared in <root>.DeepCopyIrTreeWithSymbols.copyTypeParametersFrom.<anonymous>' type=kotlin.Pair<<root>.IrTypeParameter, <root>.IrTypeParameter> origin=null
+                      TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
                         BLOCK type=kotlin.collections.MutableList<<root>.IrType> origin=null
                           CALL 'public final fun mapTo <T, R, C> (destination: C of kotlin.collections.mapTo, transform: kotlin.Function1<T of kotlin.collections.mapTo, R of kotlin.collections.mapTo>): C of kotlin.collections.mapTo declared in kotlin.collections' type=kotlin.collections.MutableList<<root>.IrType> origin=null
                             <T>: <root>.IrType

compiler/testData/ir/irText/firProblems/DeepCopyIrTree.fir.kt.txt

@@ -64,7 +64,7 @@ class DeepCopyIrTreeWithSymbols {
               return <this>.<get-typeRemapper>().remapType(type = it)
             }
 )
-          }
+          } /*~> Unit */
         }
       }
     }

compiler/testData/ir/irText/regressions/coercionInLoop.fir.ir.txt

@@ -26,6 +26,7 @@ FILE fqName:<root> fileName:/coercionInLoop.kt
                 STRING_CONCATENATION type=kotlin.String
                   CONST String type=kotlin.String value="Fail "
                   GET_VAR 'var i: kotlin.Int declared in <root>.box' type=kotlin.Int origin=null
+          TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
             BLOCK type=kotlin.Int origin=POSTFIX_INCR
               VAR IR_TEMPORARY_VARIABLE name:tmp_0 type:kotlin.Int [val]
                 GET_VAR 'var i: kotlin.Int declared in <root>.box' type=kotlin.Int origin=null

compiler/testData/ir/irText/regressions/coercionInLoop.fir.kt.txt

@@ -10,7 +10,7 @@ fun box(): String {
       val tmp_0: Int = i
       i = tmp_0.inc()
       tmp_0
-    }
+    } /*~> Unit */
   }
   return "OK"
 }