psi2ir: inferred type for 'when' is Nothing only if it's exhaustive

TODO: fix inference bug

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

@@ -88,15 +88,15 @@ class BranchingExpressionGenerator(statementGenerator: StatementGenerator) : Sta
             scope.createTemporaryVariable(it.genExpr(), "subject")
         }
 
-
         val inferredType = getInferredTypeWithImplicitCastsOrFail(expression)
 
         // TODO relies on ControlFlowInformationProvider, get rid of it
-        val isUsedAsExpression = context.bindingContext[BindingContext.USED_AS_EXPRESSION, expression] ?: false
+        val isUsedAsExpression = get(BindingContext.USED_AS_EXPRESSION, expression) ?: false
+        val isExhaustive = expression.isExhaustiveWhen()
 
         val resultType = when {
             isUsedAsExpression -> inferredType
-            KotlinBuiltIns.isNothing(inferredType) -> inferredType
+            isExhaustive && KotlinBuiltIns.isNothing(inferredType) -> inferredType
             else -> context.builtIns.unitType
         }
 
@@ -129,10 +129,8 @@ class BranchingExpressionGenerator(statementGenerator: StatementGenerator) : Sta
 
     private fun addElseBranchForExhaustiveWhenIfNeeded(irWhen: IrWhen, whenExpression: KtWhenExpression) {
         if (irWhen.branches.filterIsInstance<IrElseBranch>().isEmpty()) {
-            val bindingContext = context.bindingContext
             //TODO: check condition: seems it's safe to always generate exception
-            val isExhaustive = java.lang.Boolean.TRUE == bindingContext.get(BindingContext.IMPLICIT_EXHAUSTIVE_WHEN, whenExpression) ||
+            val isExhaustive = whenExpression.isExhaustiveWhen()
-                    java.lang.Boolean.TRUE == bindingContext.get(BindingContext.EXHAUSTIVE_WHEN, whenExpression)
 
             if (isExhaustive) {
                 val call = IrCallImpl(UNDEFINED_OFFSET, UNDEFINED_OFFSET, context.irBuiltIns.noWhenBranchMatchedExceptionSymbol)
@@ -141,6 +139,11 @@ class BranchingExpressionGenerator(statementGenerator: StatementGenerator) : Sta
         }
     }
 
+    private fun KtWhenExpression.isExhaustiveWhen(): Boolean =
+        elseExpression != null // TODO front-end should provide correct exhaustiveness information
+                || true == get(BindingContext.EXHAUSTIVE_WHEN, this)
+                || true == get(BindingContext.IMPLICIT_EXHAUSTIVE_WHEN, this)
+
     private fun generateWhenBody(expression: KtWhenExpression, irSubject: IrVariable?, irWhen: IrWhen): IrExpression {
         return if (irSubject == null) {
             if (irWhen.branches.isEmpty())
@@ -178,10 +181,14 @@ class BranchingExpressionGenerator(statementGenerator: StatementGenerator) : Sta
     }
 
     private fun generateIsPatternCondition(irSubject: IrVariable, ktCondition: KtWhenConditionIsPattern): IrExpression {
-        val isType = getOrFail(BindingContext.TYPE, ktCondition.typeReference)
+        val typeOperand = getOrFail(BindingContext.TYPE, ktCondition.typeReference)
+        val typeOperandDescriptor = typeOperand.constructor.declarationDescriptor
+                ?: throw AssertionError("No declaration descriptor for type $typeOperand")
+        val typeOperandSymbol = context.symbolTable.referenceClassifier(typeOperandDescriptor)
+
         return IrTypeOperatorCallImpl(
             ktCondition.startOffset, ktCondition.endOffset, context.builtIns.booleanType,
-            IrTypeOperator.INSTANCEOF, isType, irSubject.defaultLoad()
+            IrTypeOperator.INSTANCEOF, typeOperand, irSubject.defaultLoad(), typeOperandSymbol
         )
     }
 

compiler/testData/ir/irText/expressions/floatingPointComparisons/whenByFloatingPoint.txt

@@ -76,7 +76,7 @@ FILE fqName:<root> fileName:/whenByFloatingPoint.kt
           WHEN type=kotlin.Int origin=WHEN
             BRANCH
               if: TYPE_OP type=kotlin.Boolean origin=INSTANCEOF typeOperand=kotlin.Double
-                typeOperand: UNBOUND: class Double : kotlin.Number, kotlin.Comparable<kotlin.Double>, java.io.Serializable
+                typeOperand: CLASS IR_EXTERNAL_DECLARATION_STUB CLASS name:Double modality:FINAL visibility:public flags:
                 GET_VAR 'tmp0_subject: Any' type=kotlin.Any origin=null
               then: CONST Int type=kotlin.Int value=-1
             BRANCH

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

@@ -40,7 +40,7 @@ FILE fqName:<root> fileName:/when.kt
               then: CONST String type=kotlin.String value=A
             BRANCH
               if: TYPE_OP type=kotlin.Boolean origin=INSTANCEOF typeOperand=kotlin.String
-                typeOperand: UNBOUND: class String : kotlin.Comparable<kotlin.String>, kotlin.CharSequence, java.io.Serializable
+                typeOperand: CLASS IR_EXTERNAL_DECLARATION_STUB CLASS name:String modality:FINAL visibility:public flags:
                 GET_VAR 'tmp0_subject: Any?' type=kotlin.Any? origin=null
               then: CONST String type=kotlin.String value=String
             BRANCH

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

@@ -0,0 +1,27 @@
+fun one() = 1
+fun two() = 2
+
+fun test1(): Int {
+    while (true) {
+        when (one()) {
+            1 -> {
+                when(two()) {
+                    2 -> return 2
+                }
+            } // : Nothing
+            else -> return 3
+        }
+    }
+}
+
+fun test2(): Int {
+    while (true) {
+        when (one()) {
+            1 ->
+                when (two()) {
+                    2 -> return 2
+                } // : Unit -> Nothing
+            else -> return 3
+        } // : Nothing
+    }
+}

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

@@ -0,0 +1,68 @@
+FILE fqName:<root> fileName:/kt24114.kt
+  FUN name:one visibility:public modality:FINAL <> () returnType:Int flags:
+    BLOCK_BODY
+      RETURN type=kotlin.Nothing from='one(): Int'
+        CONST Int type=kotlin.Int value=1
+  FUN name:two visibility:public modality:FINAL <> () returnType:Int flags:
+    BLOCK_BODY
+      RETURN type=kotlin.Nothing from='two(): Int'
+        CONST Int type=kotlin.Int value=2
+  FUN name:test1 visibility:public modality:FINAL <> () returnType:Int flags:
+    BLOCK_BODY
+      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
+            VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.Int flags:val
+              CALL 'one(): Int' type=kotlin.Int origin=null
+            WHEN type=kotlin.Nothing origin=WHEN
+              BRANCH
+                if: CALL 'EQEQ(Any?, Any?): Boolean' type=kotlin.Boolean origin=EQEQ
+                  arg0: GET_VAR 'tmp0_subject: Int' type=kotlin.Int origin=null
+                  arg1: CONST Int type=kotlin.Int value=1
+                then: BLOCK type=kotlin.Nothing origin=null
+                  TYPE_OP type=kotlin.Nothing origin=IMPLICIT_CAST typeOperand=kotlin.Nothing
+                    typeOperand: CLASS IR_EXTERNAL_DECLARATION_STUB CLASS name:Nothing modality:FINAL visibility:public flags:
+                    BLOCK type=kotlin.Unit origin=WHEN
+                      VAR IR_TEMPORARY_VARIABLE name:tmp1_subject type:kotlin.Int flags:val
+                        CALL 'two(): Int' type=kotlin.Int origin=null
+                      WHEN type=kotlin.Unit origin=WHEN
+                        BRANCH
+                          if: CALL 'EQEQ(Any?, Any?): Boolean' type=kotlin.Boolean origin=EQEQ
+                            arg0: GET_VAR 'tmp1_subject: Int' type=kotlin.Int origin=null
+                            arg1: CONST Int type=kotlin.Int value=2
+                          then: RETURN type=kotlin.Nothing from='test1(): Int'
+                            CONST Int type=kotlin.Int value=2
+              BRANCH
+                if: CONST Boolean type=kotlin.Boolean value=true
+                then: RETURN type=kotlin.Nothing from='test1(): Int'
+                  CONST Int type=kotlin.Int value=3
+  FUN name:test2 visibility:public modality:FINAL <> () returnType:Int flags:
+    BLOCK_BODY
+      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
+            VAR IR_TEMPORARY_VARIABLE name:tmp0_subject type:kotlin.Int flags:val
+              CALL 'one(): Int' type=kotlin.Int origin=null
+            WHEN type=kotlin.Nothing origin=WHEN
+              BRANCH
+                if: CALL 'EQEQ(Any?, Any?): Boolean' type=kotlin.Boolean origin=EQEQ
+                  arg0: GET_VAR 'tmp0_subject: Int' type=kotlin.Int origin=null
+                  arg1: CONST Int type=kotlin.Int value=1
+                then: TYPE_OP type=kotlin.Nothing origin=IMPLICIT_CAST typeOperand=kotlin.Nothing
+                  typeOperand: CLASS IR_EXTERNAL_DECLARATION_STUB CLASS name:Nothing modality:FINAL visibility:public flags:
+                  BLOCK type=kotlin.Unit origin=WHEN
+                    VAR IR_TEMPORARY_VARIABLE name:tmp1_subject type:kotlin.Int flags:val
+                      CALL 'two(): Int' type=kotlin.Int origin=null
+                    WHEN type=kotlin.Unit origin=WHEN
+                      BRANCH
+                        if: CALL 'EQEQ(Any?, Any?): Boolean' type=kotlin.Boolean origin=EQEQ
+                          arg0: GET_VAR 'tmp1_subject: Int' type=kotlin.Int origin=null
+                          arg1: CONST Int type=kotlin.Int value=2
+                        then: RETURN type=kotlin.Nothing from='test2(): Int'
+                          CONST Int type=kotlin.Int value=2
+              BRANCH
+                if: CONST Boolean type=kotlin.Boolean value=true
+                then: RETURN type=kotlin.Nothing from='test2(): Int'
+                  CONST Int type=kotlin.Int value=3

compiler/tests/org/jetbrains/kotlin/ir/IrTextTestCaseGenerated.java

@@ -1256,6 +1256,11 @@ public class IrTextTestCaseGenerated extends AbstractIrTextTestCase {
             runTest("compiler/testData/ir/irText/regressions/integerCoercionToT.kt");
         }
 
+        @TestMetadata("kt24114.kt")
+        public void testKt24114() throws Exception {
+            runTest("compiler/testData/ir/irText/regressions/kt24114.kt");
+        }
+
         @TestMetadata("typeAliasCtorForGenericClass.kt")
         public void testTypeAliasCtorForGenericClass() throws Exception {
             runTest("compiler/testData/ir/irText/regressions/typeAliasCtorForGenericClass.kt");