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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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10
java/ql/test-kotlin2/library-tests/exprs/exprs.expected
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@@ -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 |