psi2ir: Empty 'if' branches have type 'kotlin.Unit'

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/BranchingExpressionGenerator.kt

@@ -26,7 +26,6 @@ import org.jetbrains.kotlin.ir.declarations.IrVariable
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.expressions.impl.*
 import org.jetbrains.kotlin.ir.types.IrType
-import org.jetbrains.kotlin.ir.types.classifierOrNull
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.endOffset
 import org.jetbrains.kotlin.psi.psiUtil.startOffset
@@ -51,8 +50,7 @@ class BranchingExpressionGenerator(statementGenerator: StatementGenerator) : Sta
             val irThenBranch = ktLastIf.then?.genExpr() ?: generateEmptyBlockForMissingBranch(ktLastIf)
             irBranches.add(IrBranchImpl(irCondition, irThenBranch))
 
-            val ktElse = ktLastIf.`else`?.deparenthesize()
+            when (val ktElse = ktLastIf.`else`?.deparenthesize()) {
-            when (ktElse) {
                 null -> break@whenBranches
                 is KtIfExpression -> ktLastIf = ktElse
                 is KtExpression -> {
@@ -67,7 +65,7 @@ class BranchingExpressionGenerator(statementGenerator: StatementGenerator) : Sta
     }
 
     private fun generateEmptyBlockForMissingBranch(ktLastIf: KtIfExpression) =
-        IrBlockImpl(ktLastIf.startOffset, ktLastIf.endOffset, context.irBuiltIns.nothingType, IrStatementOrigin.IF, listOf())
+        IrBlockImpl(ktLastIf.startOffset, ktLastIf.endOffset, context.irBuiltIns.unitType, IrStatementOrigin.IF, listOf())
 
     private fun createIrWhen(
         ktIf: KtIfExpression,

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

@@ -21,4 +21,41 @@ FILE fqName:<root> fileName:/ifElseIf.kt
               BRANCH
                 if: CONST Boolean type=kotlin.Boolean value=true
                 then: CONST Int type=kotlin.Int value=0
-
+  FUN name:testEmptyBranches1 visibility:public modality:FINAL <> (flag:kotlin.Boolean) returnType:kotlin.Unit
+    VALUE_PARAMETER name:flag index:0 type:kotlin.Boolean
+    BLOCK_BODY
+      WHEN type=kotlin.Unit origin=IF
+        BRANCH
+          if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches1' 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
+      WHEN type=kotlin.Unit origin=IF
+        BRANCH
+          if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches1' type=kotlin.Boolean origin=null
+          then: CONST Boolean type=kotlin.Boolean value=true
+  FUN name:testEmptyBranches2 visibility:public modality:FINAL <> (flag:kotlin.Boolean) returnType:kotlin.Unit
+    VALUE_PARAMETER name:flag index:0 type:kotlin.Boolean
+    BLOCK_BODY
+      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: 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: CONST Boolean type=kotlin.Boolean value=true
+  FUN name:testEmptyBranches3 visibility:public modality:FINAL <> (flag:kotlin.Boolean) returnType:kotlin.Unit
+    VALUE_PARAMETER name:flag index:0 type:kotlin.Boolean
+    BLOCK_BODY
+      WHEN type=kotlin.Unit origin=IF
+        BRANCH
+          if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches3' 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

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

@@ -1,4 +1,19 @@
 fun test(i: Int) =
-        if (i > 0) 1
+    if (i > 0) 1
-        else if (i < 0) -1
+    else if (i < 0) -1
-        else 0
+    else 0
+
+fun testEmptyBranches1(flag: Boolean) {
+    if (flag) ; else true
+    if (flag) true else;
+}
+
+fun testEmptyBranches2(flag: Boolean) {
+    if (flag) {} else true
+    if (flag) true else {}
+}
+
+fun testEmptyBranches3(flag: Boolean) {
+    if (flag)
+    else true
+}

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

@@ -17,3 +17,49 @@ FILE fqName:<root> fileName:/ifElseIf.kt
           BRANCH
             if: CONST Boolean type=kotlin.Boolean value=true
             then: CONST Int type=kotlin.Int value=0
+  FUN name:testEmptyBranches1 visibility:public modality:FINAL <> (flag:kotlin.Boolean) returnType:kotlin.Unit
+    VALUE_PARAMETER name:flag index:0 type:kotlin.Boolean
+    BLOCK_BODY
+      WHEN type=kotlin.Unit origin=IF
+        BRANCH
+          if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches1' type=kotlin.Boolean origin=null
+          then: BLOCK type=kotlin.Unit origin=IF
+        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>.testEmptyBranches1' 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
+  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
+  FUN name:testEmptyBranches3 visibility:public modality:FINAL <> (flag:kotlin.Boolean) returnType:kotlin.Unit
+    VALUE_PARAMETER name:flag index:0 type:kotlin.Boolean
+    BLOCK_BODY
+      WHEN type=kotlin.Unit origin=IF
+        BRANCH
+          if: GET_VAR 'flag: kotlin.Boolean declared in <root>.testEmptyBranches3' type=kotlin.Boolean origin=null
+          then: BLOCK type=kotlin.Unit origin=IF
+        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

compiler/testData/ir/irText/expressions/kt27933.txt

@@ -9,7 +9,7 @@ FILE fqName:<root> fileName:/kt27933.kt
             $this: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EXCLEQ
               arg0: GET_VAR 'var r: kotlin.String [var] declared in <root>.box' type=kotlin.String origin=null
               arg1: CONST String type=kotlin.String value=""
-          then: BLOCK type=kotlin.Nothing origin=IF
+          then: BLOCK type=kotlin.Unit origin=IF
         BRANCH
           if: CONST Boolean type=kotlin.Boolean value=true
           then: SET_VAR 'var r: kotlin.String [var] declared in <root>.box' type=kotlin.Unit origin=PLUSEQ