Java: Add test showing missing dispatch for incomplete parameterised type #19543
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Pull Request Overview
Adds a reproducer for missing virtual dispatch on error-containing generics and wires up a CodeQL query to detect it.
- Introduce a
GenericClass<T>andtestDispatchmethod inTest.javato trigger dispatch on both valid and error types. - Add
Dispatch.qlto queryviableImplofMethodCall. - Provide expected output in
Dispatch.expectedfor the successful dispatch case.
Reviewed Changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| java/ql/test/library-tests/errortype/Test.java | Added nested GenericClass<T> and testDispatch method to exercise dispatch logic |
| java/ql/test/library-tests/errortype/Dispatch.ql | New query selecting virtual dispatch (viableImpl) matches |
| java/ql/test/library-tests/errortype/Dispatch.expected | Expected single dispatch result for the String instantiation |
Comments suppressed due to low confidence (1)
java/ql/test/library-tests/errortype/Test.java:14
- The method
testDispatchis missing a return type. Update the signature to something likepublic void testDispatch()so the code compiles.
public testDispatch() {
hvitved
reviewed
May 21, 2025
| public testDispatch() { | ||
| GenericClass<String> g1 = new GenericClass<>(); | ||
| g1.method(); | ||
| GenericClass<NoSuchClass> g2 = new GenericClass<>(); |
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FWIW, the QL-based type inference/method resolution implementation should be able to handle cases like these.
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That's good to know.
smowton
reviewed
May 21, 2025
Co-authored-by: Chris Smowton <smowton@github.com>
|
Suggest trying resolving this by https://github.com/github/semmle-code/tree/smowton/wip/fix-missing-methods That fixes the database inconsistency so |
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Cf. #19538
The test is failing for a couple of reasons. The most important is that
MethodCall.getMethod()has no results for the call, i.e. the extractor has not populatedcallableBinding. It's unclear what exactly we'd want the target callable to be, but it's clear what itsgetSourceDeclaration()should be and that's what we really need. If we fix that somehow, then we'll also need to allowErrorTypeinUnification.qll, but for now that won't do anything.