Kotlin: exclude the by keyword from delegated-property locations

For a delegated property `var x: Int by ResourceDelegate()` the two
frontend paths anchor the synthesised delegate locations differently:

  - K1 (-language-version 1.9) starts them at the `by` keyword.
  - K2 (default) starts them at the delegate expression itself
    (e.g. `ResourceDelegate()`), three columns later (`by ` excluded).

The `by` keyword is syntactic glue joining the property to its delegate,
not part of the expression that is evaluated and stored, so K2's narrower
range is the more intuitive one. An existing remap already converged the
delegated-accessor *body* expressions onto the K2 span; this commit
converges the two remaining sites.

1. The `$delegate` backing field. `getDelegateFieldLocation` recovers the
   delegate expression's range from the enclosing `KtProperty` via PSI
   (available under K1; null under K2, where the raw offsets already
   exclude `by`) and is used both for the field's declaration location
   (extractField) and for its initializer assignment / lhs access
   (extractFieldInitializer's declLocId). It fires only for a delegated
   property's own backing field (`isDelegated` and `backingField === f`).

2. Local delegated properties. The `provideDelegate(...)` call and its
   `KProperty` argument in the delegate variable's initializer span the
   whole `by <expr>` range under K1; the `IrLocalDelegatedProperty`
   branch now applies the same `scopedOffsetRemap` used for accessor
   bodies while extracting that variable.

The shared PSI walk is factored into `getEnclosingKtProperty` and a
`KtProperty`-keyed `getDelegateExpressionOffsetRemap` overload.

Result: test-kotlin1 and test-kotlin2 exprs/delegatedProperties.expected
and exprs/funcExprs.expected are now byte-identical. exprs/exprs.expected
and methods/exprs.expected have their delegate rows converged (remaining
diffs in those two files are unrelated mechanisms: implicit-cast nodes and
the property-type / setter-parameter spans, addressed separately). All
3333 tests pass in both suites (K1 2.3.20 / lang 1.9 and K2 2.4.0 /
lang 2.0).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: andersfugmann

java/kotlin-extractor/src/main/kotlin/KotlinFileExtractor.kt

@@ -1610,7 +1610,7 @@ open class KotlinFileExtractor(
 
             val expr = initializer.expression
 
-            val declLocId = tw.getLocation(f)
+            val declLocId = (f as? IrField)?.let { getDelegateFieldLocation(it) } ?: tw.getLocation(f)
             extractExpressionStmt(
                     declLocId,
                     blockAndFunctionId.first,
@@ -2677,6 +2677,7 @@ open class KotlinFileExtractor(
                         ?.owner
                         ?.takeUnless { it.isDelegated }
                         ?.let { getPsiBasedLocation(it) }
+                        ?: getDelegateFieldLocation(f)
                         ?: tw.getLocation(f)
                 return extractField(
                     id,
@@ -3454,11 +3455,18 @@ open class KotlinFileExtractor(
     private fun getDelegateExpressionOffsetRemap(
         f: IrFunction
     ): Pair<Pair<Int, Int>, Pair<Int, Int>>? {
-        val file = currentIrFile ?: return null
-        val psiElement = getPsi2Ir()?.findPsiElement(f, file) ?: return null
-        val ktProperty = generateSequence(psiElement) { it.parent }
-            .filterIsInstance<KtProperty>().firstOrNull()
-            ?: return null
+        return getEnclosingKtProperty(f)?.let { getDelegateExpressionOffsetRemap(it) }
+    }
+
+    /**
+     * Maps the whole `by <expr>` delegate range (which the K1 frontend records for the
+     * synthesised delegate expressions) onto the delegate expression's own range (the `by`
+     * keyword excluded, as K2 records natively). Returns null when [ktProperty] has no delegate
+     * or the delegate has no expression.
+     */
+    private fun getDelegateExpressionOffsetRemap(
+        ktProperty: KtProperty
+    ): Pair<Pair<Int, Int>, Pair<Int, Int>>? {
         val delegate = ktProperty.delegate ?: return null
         val expression = delegate.expression ?: return null
         return Pair(
@@ -3467,6 +3475,40 @@ open class KotlinFileExtractor(
         )
     }
 
+    /**
+     * Returns the [KtProperty] enclosing the PSI element that back-maps from IR element [e],
+     * or null when no PSI is available (as under K2, where [getKtFile]/[findPsiElement] return
+     * null) or [e] is not within a property.
+     */
+    private fun getEnclosingKtProperty(e: IrElement): KtProperty? {
+        val file = currentIrFile ?: return null
+        val psiElement = getPsi2Ir()?.findPsiElement(e, file) ?: return null
+        return generateSequence(psiElement) { it.parent }
+            .filterIsInstance<KtProperty>().firstOrNull()
+    }
+
+    /**
+     * Returns the PSI-based location for a delegated property's `$delegate` backing field, or
+     * null to leave the raw IR offset in place.
+     *
+     * The `$delegate` field stores the delegate object, so its natural location is the delegate
+     * expression (e.g. `ResourceDelegate()` in `by ResourceDelegate()`). The K1 frontend's raw
+     * offset for this field starts at the `by` keyword; K2 starts at the delegate expression.
+     * The `by` keyword is syntactic glue, not part of the stored expression, so K2's narrower
+     * range is the more intuitive one.
+     *
+     * This fires only for a delegated property's own backing field (`isDelegated` and
+     * `backingField === f`), and returns null under K2 (no PSI) and for specialised/binary
+     * extractions (no PSI), where the raw offset already excludes the `by` keyword.
+     */
+    private fun getDelegateFieldLocation(f: IrField): Label<DbLocation>? {
+        val property = f.correspondingPropertySymbol?.owner ?: return null
+        if (!property.isDelegated || property.backingField !== f) return null
+        val ktProperty = getEnclosingKtProperty(property) ?: return null
+        val expression = ktProperty.delegate?.expression ?: return null
+        return tw.getLocation(expression.startOffset, expression.endOffset)
+    }
+
     /**
      * Reconstructs the location of an `if`/`when` branch [b] (of the enclosing [IrWhen] [w])
      * from the branch's own condition/result offsets, or null to leave the raw location in
@@ -3673,7 +3715,19 @@ open class KotlinFileExtractor(
                             // This is not expected to happen, as the plugin hooks into the pipeline before IR lowering.
                             logger.errorElement("Local delegated property is missing delegate", s)
                         } else {
-                            extractVariable(delegate, callable, blockId, 0)
+                            // The synthesised `provideDelegate(...)` call and its `KProperty`
+                            // argument in the delegate variable's initializer span the whole
+                            // `by <expr>` range under K1; remap them onto the delegate
+                            // expression (the `by` keyword excluded, as K2 records natively).
+                            val delegateRemap =
+                                getEnclosingKtProperty(s)?.let { getDelegateExpressionOffsetRemap(it) }
+                            val previousRemap = tw.scopedOffsetRemap
+                            if (delegateRemap != null) tw.scopedOffsetRemap = delegateRemap
+                            try {
+                                extractVariable(delegate, callable, blockId, 0)
+                            } finally {
+                                tw.scopedOffsetRemap = previousRemap
+                            }
                             tw.writeKtProperties(propId, s.name.asString())
                             tw.writeHasLocation(propId, locId)
                             tw.writeKtPropertyDelegates(propId, useVariable(delegate))

java/ql/test-kotlin1/library-tests/exprs/delegatedProperties.expected

@@ -4,19 +4,19 @@ delegatedProperties
 | delegatedProperties.kt:23:9:23:31 | name | name | local | delegatedProperties.kt:23:9:23:31 | Map<String,Object> name$delegate | delegatedProperties.kt:23:29:23:31 | map |
 | delegatedProperties.kt:33:9:33:76 | readOnly | readOnly | local | delegatedProperties.kt:33:9:33:76 | ReadWriteProperty<Object,Integer> readOnly$delegate | delegatedProperties.kt:33:30:33:47 | resourceDelegate(...) |
 | delegatedProperties.kt:34:9:34:48 | readWrite | readWrite | local | delegatedProperties.kt:34:9:34:48 | ReadWriteProperty<Object,Integer> readWrite$delegate | delegatedProperties.kt:34:31:34:48 | resourceDelegate(...) |
-| delegatedProperties.kt:39:9:39:51 | varResource2 | varResource2 | local | delegatedProperties.kt:39:9:39:51 | ResourceDelegate varResource2$delegate | delegatedProperties.kt:39:31:39:51 | provideDelegate(...) |
-| delegatedProperties.kt:42:5:42:47 | varResource0 | varResource0 | non-local | delegatedProperties.kt:42:27:42:47 | varResource0$delegate | delegatedProperties.kt:42:30:42:47 | new ResourceDelegate(...) |
-| delegatedProperties.kt:66:5:66:50 | delegatedToMember1 | delegatedToMember1 | non-local | delegatedProperties.kt:66:33:66:50 | delegatedToMember1$delegate | delegatedProperties.kt:66:36:66:50 | ...::... |
-| delegatedProperties.kt:67:5:67:53 | delegatedToMember2 | delegatedToMember2 | non-local | delegatedProperties.kt:67:33:67:53 | delegatedToMember2$delegate | delegatedProperties.kt:67:36:67:53 | ...::... |
-| delegatedProperties.kt:69:5:69:56 | delegatedToExtMember1 | delegatedToExtMember1 | non-local | delegatedProperties.kt:69:36:69:56 | delegatedToExtMember1$delegate | delegatedProperties.kt:69:39:69:56 | ...::... |
-| delegatedProperties.kt:70:5:70:59 | delegatedToExtMember2 | delegatedToExtMember2 | non-local | delegatedProperties.kt:70:36:70:59 | delegatedToExtMember2$delegate | delegatedProperties.kt:70:39:70:59 | ...::... |
-| delegatedProperties.kt:72:5:72:56 | delegatedToBaseClass1 | delegatedToBaseClass1 | non-local | delegatedProperties.kt:72:36:72:56 | delegatedToBaseClass1$delegate | delegatedProperties.kt:72:39:72:56 | ...::... |
-| delegatedProperties.kt:73:5:73:56 | delegatedToBaseClass2 | delegatedToBaseClass2 | non-local | delegatedProperties.kt:73:36:73:56 | delegatedToBaseClass2$delegate | delegatedProperties.kt:73:39:73:56 | ...::... |
-| delegatedProperties.kt:75:5:75:78 | delegatedToAnotherClass1 | delegatedToAnotherClass1 | non-local | delegatedProperties.kt:75:39:75:78 | delegatedToAnotherClass1$delegate | delegatedProperties.kt:75:42:75:78 | ...::... |
-| delegatedProperties.kt:77:5:77:49 | delegatedToTopLevel | delegatedToTopLevel | non-local | delegatedProperties.kt:77:34:77:49 | delegatedToTopLevel$delegate | delegatedProperties.kt:77:37:77:49 | ...::... |
-| delegatedProperties.kt:79:5:79:38 | max | max | non-local | delegatedProperties.kt:79:18:79:38 | max$delegate | delegatedProperties.kt:79:21:79:38 | ...::... |
+| delegatedProperties.kt:39:9:39:51 | varResource2 | varResource2 | local | delegatedProperties.kt:39:9:39:51 | ResourceDelegate varResource2$delegate | delegatedProperties.kt:39:34:39:51 | provideDelegate(...) |
+| delegatedProperties.kt:42:5:42:47 | varResource0 | varResource0 | non-local | delegatedProperties.kt:42:30:42:47 | varResource0$delegate | delegatedProperties.kt:42:30:42:47 | new ResourceDelegate(...) |
+| delegatedProperties.kt:66:5:66:50 | delegatedToMember1 | delegatedToMember1 | non-local | delegatedProperties.kt:66:36:66:50 | delegatedToMember1$delegate | delegatedProperties.kt:66:36:66:50 | ...::... |
+| delegatedProperties.kt:67:5:67:53 | delegatedToMember2 | delegatedToMember2 | non-local | delegatedProperties.kt:67:36:67:53 | delegatedToMember2$delegate | delegatedProperties.kt:67:36:67:53 | ...::... |
+| delegatedProperties.kt:69:5:69:56 | delegatedToExtMember1 | delegatedToExtMember1 | non-local | delegatedProperties.kt:69:39:69:56 | delegatedToExtMember1$delegate | delegatedProperties.kt:69:39:69:56 | ...::... |
+| delegatedProperties.kt:70:5:70:59 | delegatedToExtMember2 | delegatedToExtMember2 | non-local | delegatedProperties.kt:70:39:70:59 | delegatedToExtMember2$delegate | delegatedProperties.kt:70:39:70:59 | ...::... |
+| delegatedProperties.kt:72:5:72:56 | delegatedToBaseClass1 | delegatedToBaseClass1 | non-local | delegatedProperties.kt:72:39:72:56 | delegatedToBaseClass1$delegate | delegatedProperties.kt:72:39:72:56 | ...::... |
+| delegatedProperties.kt:73:5:73:56 | delegatedToBaseClass2 | delegatedToBaseClass2 | non-local | delegatedProperties.kt:73:39:73:56 | delegatedToBaseClass2$delegate | delegatedProperties.kt:73:39:73:56 | ...::... |
+| delegatedProperties.kt:75:5:75:78 | delegatedToAnotherClass1 | delegatedToAnotherClass1 | non-local | delegatedProperties.kt:75:42:75:78 | delegatedToAnotherClass1$delegate | delegatedProperties.kt:75:42:75:78 | ...::... |
+| delegatedProperties.kt:77:5:77:49 | delegatedToTopLevel | delegatedToTopLevel | non-local | delegatedProperties.kt:77:37:77:49 | delegatedToTopLevel$delegate | delegatedProperties.kt:77:37:77:49 | ...::... |
+| delegatedProperties.kt:79:5:79:38 | max | max | non-local | delegatedProperties.kt:79:21:79:38 | max$delegate | delegatedProperties.kt:79:21:79:38 | ...::... |
 | delegatedProperties.kt:82:9:82:54 | delegatedToMember3 | delegatedToMember3 | local | delegatedProperties.kt:82:9:82:54 | KMutableProperty0<Integer> delegatedToMember3$delegate | delegatedProperties.kt:82:40:82:54 | ...::... |
-| delegatedProperties.kt:87:1:87:46 | extDelegated | extDelegated | non-local | delegatedProperties.kt:87:31:87:46 | extDelegated$delegateMyClass | delegatedProperties.kt:87:34:87:46 | ...::... |
+| delegatedProperties.kt:87:1:87:46 | extDelegated | extDelegated | non-local | delegatedProperties.kt:87:34:87:46 | extDelegated$delegateMyClass | delegatedProperties.kt:87:34:87:46 | ...::... |
 delegatedPropertyTypes
 | delegatedProperties.kt:6:9:9:9 | prop1 | file://:0:0:0:0 | int | file://<external>/Lazy.class:0:0:0:0 | Lazy<Integer> |
 | delegatedProperties.kt:19:9:19:51 | varResource1 | file://:0:0:0:0 | int | delegatedProperties.kt:45:1:51:1 | ResourceDelegate |