github / github/codeql-cli-binaries

Should create warning or error for inherited unusable predicates

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Description

Currently CodeQL permits writing classes with predicates using database queries, and then subclasses which do not fulfill the requirements for these database types. This renders these inherited predicates unusable and creates pretty cryptic compilation errors when trying to use them. Examples:
- https://github.com/github/codeql/issues/3705
- https://github.com/github/codeql/issues/5320
- https://github.com/github/codeql/issues/7067

It would be good if:
1. The CodeQL compiler would detect such unusuable inherited predicates and cause a compilation error (or at least a warning) for the subclass. This would avoid exposing such subclasses to the user, causing the cryptic compilation errors when they try to use predicates of the subclass.
2. The error message would be clearer, ideally pointing to where the requirement for the database types come from, with predicate call hierarchy if possible. For example for CodeQL Java's `Array.getQualifiedName()` (see https://github.com/github/codeql/issues/7067) it should indicate that `RefType.getPackage()` only supports `@class` and `@interface`.

Contributor guide

Open the contributing guide

Research direction

Start by reproducing the inherited-predicate cases in issues #3705, #5320, and #7067, including CodeQL Java's Array.getQualifiedName() and RefType.getPackage(). Trace how the compiler handles database-type requirements and predicate call hierarchy. Done means unusable inherited predicates are rejected or warned about with a clear diagnostic identifying the originating requirement.

Written by the indexing model from the issue text.

Assessment

Domain
compilers
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
20/100

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