Make HeaderInfo.step not nullable and have handlers explicitly provide

the step expression.

The semantics of "step" are now clearer: It will no longer be negated
based on the "increasing" property; if the progression is decreasing
(i.e., for "downTo" progressions), then it must be negative. The
"increasing" property is still used when building the emptiness
condition.

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/loops/HeaderInfo.kt

@@ -9,7 +9,6 @@ import org.jetbrains.kotlin.backend.common.CommonBackendContext
 import org.jetbrains.kotlin.backend.common.ir.Symbols
 import org.jetbrains.kotlin.backend.common.lower.matchers.IrCallMatcher
 import org.jetbrains.kotlin.ir.IrElement
-import org.jetbrains.kotlin.ir.declarations.IrValueDeclaration
 import org.jetbrains.kotlin.ir.declarations.IrVariable
 import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
 import org.jetbrains.kotlin.ir.expressions.IrCall
@@ -52,7 +51,7 @@ internal sealed class HeaderInfo(
     val progressionType: ProgressionType,
     val lowerBound: IrExpression,
     val upperBound: IrExpression,
-    val step: IrExpression?, // null value denotes default step (1)
+    val step: IrExpression,
     val increasing: Boolean,
     val closed: Boolean
 )
@@ -61,7 +60,7 @@ internal class ProgressionHeaderInfo(
     progressionType: ProgressionType,
     lowerBound: IrExpression,
     upperBound: IrExpression,
-    step: IrExpression? = null,
+    step: IrExpression,
     increasing: Boolean = true,
     closed: Boolean = true
 ) : HeaderInfo(progressionType, lowerBound, upperBound, step, increasing, closed)
@@ -69,12 +68,13 @@ internal class ProgressionHeaderInfo(
 internal class ArrayHeaderInfo(
     lowerBound: IrExpression,
     upperBound: IrExpression,
-    val arrayDeclaration: IrValueDeclaration
+    step: IrExpression,
+    val arrayVariable: IrVariable
 ) : HeaderInfo(
     ProgressionType.INT_PROGRESSION,
     lowerBound,
     upperBound,
-    step = null,
+    step,
     increasing = true,
     closed = false
 )
@@ -102,9 +102,9 @@ private class ProgressionHeaderInfoBuilder(val context: CommonBackendContext) :
 
     private val progressionHandlers = listOf(
         IndicesHandler(context),
-        UntilHandler(progressionElementTypes),
-        DownToHandler(progressionElementTypes),
-        RangeToHandler(progressionElementTypes)
+        UntilHandler(context, progressionElementTypes),
+        DownToHandler(context, progressionElementTypes),
+        RangeToHandler(context, progressionElementTypes)
     )
 
     override fun visitElement(element: IrElement, data: Nothing?): HeaderInfo? = null

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/loops/HeaderProcessor.kt

@@ -19,7 +19,6 @@ import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
 import org.jetbrains.kotlin.ir.expressions.IrExpression
 import org.jetbrains.kotlin.ir.expressions.IrLoop
 import org.jetbrains.kotlin.ir.expressions.impl.IrCallImpl
-import org.jetbrains.kotlin.ir.expressions.impl.IrConstImpl
 import org.jetbrains.kotlin.ir.expressions.impl.IrDoWhileLoopImpl
 import org.jetbrains.kotlin.ir.expressions.impl.IrWhileLoopImpl
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
@@ -93,7 +92,7 @@ internal class ArrayLoopHeader(
     step: IrVariable
 ) : ForLoopHeader(inductionVariable, bound, last, step, ProgressionType.INT_PROGRESSION) {
 
-    private val arrayDeclaration = headerInfo.arrayDeclaration
+    private val arrayDeclaration = headerInfo.arrayVariable
 
     override fun initializeLoopVariable(symbols: Symbols<CommonBackendContext>, builder: DeclarationIrBuilder) = with(builder) {
         val arrayClass = (arrayDeclaration.type.classifierOrNull) as IrClassSymbol
@@ -143,7 +142,7 @@ internal class HeaderProcessor(
         val progressionInfo = headerInfoBuilder.build(variable)
             ?: return null
         if (progressionInfo is ArrayHeaderInfo) {
-            progressionInfo.arrayDeclaration.parent = variable.parent
+            progressionInfo.arrayVariable.parent = variable.parent
         }
         with(builder) {
             with(progressionInfo) {
@@ -168,11 +167,7 @@ internal class HeaderProcessor(
                     origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE
                 )
 
-                val stepExpression = if (step != null) {
-                    ensureNotNullable(if (increasing) step else step.unaryMinus())
-                } else {
-                    defaultStep(startOffset, endOffset)
-                }
+                val stepExpression = ensureNotNullable(step)
 
                 val stepValue = scope.createTemporaryVariable(
                     stepExpression,
@@ -237,23 +232,4 @@ internal class HeaderProcessor(
         } else {
             expression
         }
-
-    private fun IrExpression.unaryMinus(): IrExpression {
-        val unaryOperator = symbols.getUnaryOperator(OperatorNameConventions.UNARY_MINUS, type.toKotlinType())
-        return IrCallImpl(startOffset, endOffset, unaryOperator.owner.returnType, unaryOperator).apply {
-            dispatchReceiver = this@unaryMinus
-        }
-    }
-
-    private fun HeaderInfo.defaultStep(startOffset: Int, endOffset: Int): IrExpression {
-        val type = progressionType.elementType(context.irBuiltIns)
-        val step = if (increasing) 1 else -1
-        return when {
-            type.isInt() || type.isChar() ->
-                IrConstImpl.int(startOffset, endOffset, context.irBuiltIns.intType, step)
-            type.isLong() ->
-                IrConstImpl.long(startOffset, endOffset, context.irBuiltIns.longType, step.toLong())
-            else -> throw IllegalArgumentException()
-        }
-    }
 }

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/loops/ProgressionHandlers.kt

@@ -14,16 +14,19 @@ import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.ir.builders.irCall
 import org.jetbrains.kotlin.ir.builders.irGet
 import org.jetbrains.kotlin.ir.builders.irInt
-import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.expressions.IrCall
+import org.jetbrains.kotlin.ir.expressions.IrStatementOrigin
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
-import org.jetbrains.kotlin.ir.types.*
+import org.jetbrains.kotlin.ir.types.classifierOrNull
+import org.jetbrains.kotlin.ir.types.toKotlinType
 import org.jetbrains.kotlin.ir.util.properties
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.types.SimpleType
 
 // TODO: What if functions like Int.rangeTo(Char) will be added to stdlib later?
-internal class RangeToHandler(val progressionElementTypes: Collection<SimpleType>) : ProgressionHandler {
+internal class RangeToHandler(private val context: CommonBackendContext, private val progressionElementTypes: Collection<SimpleType>) :
+    ProgressionHandler {
     override val matcher = SimpleCalleeMatcher {
         dispatchReceiver { it != null && it.type.toKotlinType() in progressionElementTypes }
         fqName { it.pathSegments().last() == Name.identifier("rangeTo") }
@@ -32,49 +35,64 @@ internal class RangeToHandler(val progressionElementTypes: Collection<SimpleType
     }
 
     override fun build(call: IrCall, data: ProgressionType) =
-        ProgressionHeaderInfo(data, call.dispatchReceiver!!, call.getValueArgument(0)!!)
+        with(context.createIrBuilder(call.symbol, call.startOffset, call.endOffset)) {
+            ProgressionHeaderInfo(
+                data,
+                lowerBound = call.dispatchReceiver!!,
+                upperBound = call.getValueArgument(0)!!,
+                step = irInt(1)
+            )
+        }
 }
 
-internal class DownToHandler(val progressionElementTypes: Collection<SimpleType>) : ProgressionHandler {
+internal class DownToHandler(private val context: CommonBackendContext, private val progressionElementTypes: Collection<SimpleType>) :
+    ProgressionHandler {
     override val matcher = SimpleCalleeMatcher {
         singleArgumentExtension(FqName("kotlin.ranges.downTo"), progressionElementTypes)
+        parameterCount { it == 1 }
         parameter(0) { it.type.toKotlinType() in progressionElementTypes }
     }
 
     override fun build(call: IrCall, data: ProgressionType): HeaderInfo? =
-        ProgressionHeaderInfo(
-            data,
-            call.extensionReceiver!!,
-            call.getValueArgument(0)!!,
-            increasing = false
-        )
+        with(context.createIrBuilder(call.symbol, call.startOffset, call.endOffset)) {
+            ProgressionHeaderInfo(
+                data,
+                lowerBound = call.extensionReceiver!!,
+                upperBound = call.getValueArgument(0)!!,
+                step = irInt(-1),
+                increasing = false
+            )
+        }
 }
 
-internal class UntilHandler(val progressionElementTypes: Collection<SimpleType>) : ProgressionHandler {
+internal class UntilHandler(private val context: CommonBackendContext, private val progressionElementTypes: Collection<SimpleType>) :
+    ProgressionHandler {
     override val matcher = SimpleCalleeMatcher {
         singleArgumentExtension(FqName("kotlin.ranges.until"), progressionElementTypes)
+        parameterCount { it == 1 }
         parameter(0) { it.type.toKotlinType() in progressionElementTypes }
     }
 
     override fun build(call: IrCall, data: ProgressionType): HeaderInfo? =
-        ProgressionHeaderInfo(
-            data,
-            call.extensionReceiver!!,
-            call.getValueArgument(0)!!,
-            closed = false
-        )
+        with(context.createIrBuilder(call.symbol, call.startOffset, call.endOffset)) {
+            ProgressionHeaderInfo(
+                data,
+                lowerBound = call.extensionReceiver!!,
+                upperBound = call.getValueArgument(0)!!,
+                step = irInt(1),
+                closed = false
+            )
+        }
 }
 
 internal class IndicesHandler(val context: CommonBackendContext) : ProgressionHandler {
 
-    override val matcher = createIrCallMatcher {
-        callee {
-            fqName { it == FqName("kotlin.collections.<get-indices>") }
-            parameterCount { it == 0 }
-        }
+    override val matcher = SimpleCalleeMatcher {
         // TODO: Handle Collection<*>.indices
         // TODO: Handle CharSequence.indices
         extensionReceiver { it != null && KotlinBuiltIns.isArrayOrPrimitiveArray(it.type.toKotlinType()) }
+        fqName { it == FqName("kotlin.collections.<get-indices>") }
+        parameterCount { it == 0 }
     }
 
     override fun build(call: IrCall, data: ProgressionType): HeaderInfo? =
@@ -85,7 +103,13 @@ internal class IndicesHandler(val context: CommonBackendContext) : ProgressionHa
             val upperBound = irCall(arraySizeProperty.getter!!).apply {
                 dispatchReceiver = call.extensionReceiver
             }
-            ProgressionHeaderInfo(data, lowerBound, upperBound, closed = false)
+            ProgressionHeaderInfo(
+                data,
+                lowerBound,
+                upperBound,
+                step = irInt(1),
+                closed = false
+            )
         }
 
 }
@@ -114,6 +138,11 @@ internal class ArrayIterationHandler(val context: CommonBackendContext) : Header
             val upperBound = irCall(arraySizeProperty.getter!!).apply {
                 dispatchReceiver = irGet(arrayReference)
             }
-            ArrayHeaderInfo(irInt(0), upperBound, arrayReference)
+            ArrayHeaderInfo(
+                lowerBound = irInt(0),
+                upperBound = upperBound,
+                step = irInt(1),
+                arrayVariable = arrayReference
+            )
         }
 }