When completions are inherited by elements inside `finally` blocks, we previously
threw away the underlying completion. For example, in
```
try
{
if (b)
throw new Exception();
}
finally
{
if (b)
...
}
```
the completions for `b` inside the `finally` block are `true` and `throw(Exception)`,
where the latter is inherited from the `try` block, with an underlying `false`
completion. Throwing away the `false` completion meant that we were unable to prune
the `false` edge (Boolean CFG splitting).
- Make `InstructionViolation` abstract to avoid computing `getInstructionsUpTo()`
for all instructions in the database.
- Enable `consistency.ql`, which reports all consistency violations, and remove
all other specialized tests.
- 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.
For methods compiled without optimization (and possibly also with optimization),
it is possible for a variable update to have multiple possible assigned values.
For example, the non-optimized CIL for
```
return cond ? null : "not null"
```
is
```
0: nop
1: ldarg.0
2: ldfld cond
3: brtrue.s 6:
4: ldstr "not null"
5: br.s 7:
6: ldnull
7: stloc.0 L0 // stores either `null` or "not null"
8: br.s 9:
9: ldloc.0
10: ret
```
Consequently, an existential in `CallableReturns.qll` must be a `forex`.
- 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.
