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Kotlin: locate in-place-update LHS at the variable, not the whole assignment

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For a desugared in-place update such as `v += e` the extractor emits an
`AssignAddExpr` (etc.) whose left-hand side is a `VarAccess` of `v`. The
location of that `VarAccess` was taken from the underlying `IrSetValue`
node (`getLocation(e)`). The two frontends record that node's end offset
differently: K1 ends it at the left-hand side (so the access spanned just
`v`), whereas K2 ends it past the whole assignment (so the access spanned
all of `v += e`, redundantly identical to its parent `AssignAddExpr`).

The K1 span is the more intuitive and information-preserving one: a
variable access should point at the variable reference, not repeat the
enclosing assignment's span. Converge K2 onto it.

The desugaring represents `v += e` as `v = get(v).op(e)`, so the update's
right-hand call already contains an `IrGetValue` receiver that reads `v`.
That receiver's source span is exactly the `v` identifier in both
frontends, which makes it a frontend-independent anchor for the LHS
location. `getUpdateInPlaceReceiver` recovers it (mirroring the existing
`getUpdateInPlaceRHS`), and the LHS `VarAccess` is located there. This is
fail-closed: when the node is not such an in-place update, or the receiver
lacks a usable (non-synthetic, defined) source span, the raw
`getLocation(e)` is kept. Under K1 the recovered span equals the previous
one, so K1 output is unchanged.

Only the five in-place operators in the `test-kotlin2` `exprs` test change,
each narrowing the LHS `updated` `VarAccess` from `270:3:270:14` (the whole
`updated += 1`) to `270:3:270:9` (the identifier), matching `test-kotlin1`
exactly. Prefix/postfix increment/decrement use a different desugaring
(with a temporary) and are not in-place updates in this sense; they are
left for a separate change.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Anders Fugmann
2026-07-14 05:14:05 +02:00
parent 70e5761053
commit 4e3a2f6d33
2 changed files with 37 additions and 6 deletions
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33
java/kotlin-extractor/src/main/kotlin/KotlinFileExtractor.kt
View File

@@ -6292,6 +6292,22 @@ open class KotlinFileExtractor(
else -> null
}
/**
* For a desugared in-place update such as `v += e` (represented as `v = get(v).op(e)`),
* returns the `IrGetValue` receiver that reads `v`. Its source span is the left-hand-side
* variable reference (the identifier only) in both the K1 and K2 frontends, so it provides a
* frontend-independent location for the update's LHS `VarAccess`. Returns null when [e] is not
* such an in-place update, in which case callers keep the raw location.
*/
private fun getUpdateInPlaceReceiver(e: IrSetValue): IrGetValue? {
val op = getStatementOriginOperator(e.origin) ?: return null
val rhs = e.value
if (rhs !is IrCall || !isNumericFunction(rhs.symbol.owner, op)) return null
val receiver = rhs.dispatchReceiver
return if (receiver is IrGetValue && receiver.symbol.owner == e.symbol.owner) receiver
else null
}
private fun getUpdateInPlaceRHS(
origin: IrStatementOrigin?,
isExpectedLhs: (IrExpression?) -> Boolean,
@@ -7065,7 +7081,22 @@ open class KotlinFileExtractor(
extractExprContext(id, locId, callable, exprParent.enclosingStmt)
val lhsId = tw.getFreshIdLabel<DbVaraccess>()
val lhsLocId = tw.getLocation(e)
// For a desugared in-place update (`v += e`) the K2 frontend records the set
// operation's end offset past the whole assignment, so `getLocation(e)` would
// span `v += e` rather than just `v`. Locate the LHS `VarAccess` at the update's
// receiver read of `v` instead, whose span is the identifier in both frontends;
// fall back to the raw location when this is not such an in-place update or the
// receiver lacks a usable source span.
val lhsLocId =
(e as? IrSetValue)
?.let { getUpdateInPlaceReceiver(it) }
?.takeIf {
it.startOffset != UNDEFINED_OFFSET &&
it.endOffset != UNDEFINED_OFFSET &&
it.startOffset != SYNTHETIC_OFFSET &&
it.endOffset != SYNTHETIC_OFFSET
}
?.let { tw.getLocation(it) } ?: tw.getLocation(e)
extractExprContext(lhsId, lhsLocId, callable, exprParent.enclosingStmt)
when (e) {

10
java/ql/test-kotlin2/library-tests/exprs/exprs.expected
View File

@@ -1743,20 +1743,20 @@
| exprs.kt:267:1:276:1 | Unit | file://:0:0:0:0 | <none> | TypeAccess |
| exprs.kt:269:3:269:17 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | LocalVariableDeclExpr |
| exprs.kt:269:17:269:17 | 0 | exprs.kt:267:1:276:1 | inPlaceOperators | IntegerLiteral |
| exprs.kt:270:3:270:9 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:270:3:270:14 | ...+=... | exprs.kt:267:1:276:1 | inPlaceOperators | AssignAddExpr |
| exprs.kt:270:3:270:14 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:270:14:270:14 | 1 | exprs.kt:267:1:276:1 | inPlaceOperators | IntegerLiteral |
| exprs.kt:271:3:271:9 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:271:3:271:14 | ...-=... | exprs.kt:267:1:276:1 | inPlaceOperators | AssignSubExpr |
| exprs.kt:271:3:271:14 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:271:14:271:14 | 1 | exprs.kt:267:1:276:1 | inPlaceOperators | IntegerLiteral |
| exprs.kt:272:3:272:9 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:272:3:272:14 | ...*=... | exprs.kt:267:1:276:1 | inPlaceOperators | AssignMulExpr |
| exprs.kt:272:3:272:14 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:272:14:272:14 | 1 | exprs.kt:267:1:276:1 | inPlaceOperators | IntegerLiteral |
| exprs.kt:273:3:273:9 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:273:3:273:14 | .../=... | exprs.kt:267:1:276:1 | inPlaceOperators | AssignDivExpr |
| exprs.kt:273:3:273:14 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:273:14:273:14 | 1 | exprs.kt:267:1:276:1 | inPlaceOperators | IntegerLiteral |
| exprs.kt:274:3:274:9 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:274:3:274:14 | ...%=... | exprs.kt:267:1:276:1 | inPlaceOperators | AssignRemExpr |
| exprs.kt:274:3:274:14 | updated | exprs.kt:267:1:276:1 | inPlaceOperators | VarAccess |
| exprs.kt:274:14:274:14 | 1 | exprs.kt:267:1:276:1 | inPlaceOperators | IntegerLiteral |
| exprs.kt:278:8:278:66 | T | file://:0:0:0:0 | <none> | TypeAccess |
| exprs.kt:278:8:278:66 | T[] | file://:0:0:0:0 | <none> | TypeAccess |