This currently relies on the fact that qltest includes `ql/csharp/ql/src/Metrics` in addition to `ql/csharp/ql/src` on its search path when run internally, which is inconsistent with the other languages. Since this is the only test that relies on it, I'd like to update it and get rid of the extra search root eventually.
- Add `Caching.qll` for controlling caching across multiple files.
- Move `isUncertainRefCall()` out of cached module in `Assignable.qll` to avoid
collapsing with CFG stage.
- Remove dependency on `AlwaysNullExpr` in `NullValue::getAnExpr()` to avoid
collapsing with CFG stage.
- Avoid caching pre-SSA library as it should only be used during the CFG construction
stage.
- Extract names of properties in a propery match, using the `exprorstmt_name` relation.
- Simplify extraction of properties by not distinguishing between top-level patterns
and nested patterns.
- Introduce `PatternExpr` to capture patterns in `is` expressions, `case` statements,
and `switch` expression arms.
- Generalize `IsTypeExpr`, `IsPatternExpr`, `IsRecursivePatternExpr`, and `IsConstantExpr`
to just `IsExpr` with a member predicate `PatternExpr getPattern()`.
- Generalize `TypeCase`, `RecursivePatternCase`, and `ConstCase` to just `CaseStmt` with
a member predicate `PatternExpr getPattern()`.
- Introduce classes `Switch` and `Case` as base classes of switch statements/expressions
and case statements/switch expression arms, respectively.
- Simplify CFG logic using the generalized classes.
- Generalize guards library to cover `switch` expressions tests.
- Generalize data flow library to cover `switch` expression assignments.
- General refactoring to fit with the shared data flow implementation.
- Move CFG splitting logic into `ControlFlowReachability.qll`.
- Replace `isAdditionalFlowStepIntoCall()` with `TaintedParameterNode`.
- Redefine `ReturnNode` to be the actual values that are returned, which should
yield better path information.
- No longer consider overrides in CIL calls.
- Cache predicates in the same stage using a cached module.
- Introduce `DefUse::defUseVariableUpdate()` and use in `CallableReturns.qll`.
The updated file `csharp/ql/test/library-tests/cil/dataflow/Nullness.expected`
demonstrates why this is needed.
- Utilize CIL analysis in `Guards::nonNullValue()`.
- Analyze SSA definitions in `AlwaysNullExpr`, similar to `NonNullExpr`.
