In `x with { Foo = bar }`, instead of having a single data-flow step
`x => x with { Foo = bar }`
we now have two steps:
`x => { Foo = bar }`
and
`{ Foo = bar } => x with { Foo = bar }`
Moreover, `clearsContent` now targets the object initializer instead of the
whole `with` expression, which means that it will only apply to values carried
over from the old object and not those explicitly stored into the new object.
- Introduce `ReadTaintNode` and `TaintStoreNode` to simplify logic for taint
getters and taint setters, respectively.
- `nodeCandFwd2`: Restrict `stored` column after a read, based on what it might
be before a store of the same field.
- `nodeCand2`: Restrict `read` column (renamed from `stored`) after a store, based
on what it might be after a read of the same field.
- Move big step predicates into a `LocalFlowBigStep` module.
- Define predicates by dispatch in `AccessPath[Front]` class.
- `flowCandFwd0`: Restrict `apf` column after a read, as it should be able to match
a Boolean `read` column from `nodeCand2`.
- `flowFwd0`: Restrict columns `ap` and `apf` after a read, by introducing a
`flowConsCandFwd` predicate (similar to what is done in the previous pruning steps).
- `flowFwd0`: Restrict columns `ap` and `apf` after a store, by introducing a
`flowConsCand` predicate (similar to what is done in the previous pruning steps).
The predicate
```
argumentValueFlowsThrough(ArgumentNode arg, OutNode out, CallContext cc)
```
has been generalized to
```
argumentValueFlowsThrough(
DataFlowCall call, ArgumentNode arg, Node out, ContentOption contentIn,
ContentOption contentOut
)
```
This enables us to summarize normal flow-through (as before), getters, setters,
as well as getter-setters.
This commit adds type information to data flow paths, by mapping node types onto
the smaller set of GVN types, and implementing `ppReprType()`.
The effect is a mere change in `DataFlow::PathNode::toString()`; no type-based
pruning is done yet.
This commit adds field initializers to the CFG for non-static constructors. For
example, in
```
class C
{
int Field1 = 0;
int Field2 = Field1 + 1;
int Field3;
public C()
{
Field3 = 2;
}
public C(int i)
{
Field3 = 3;
}
}
```
the initializer expressions `Field1 = 0` and `Field2 = Field1 + 1` are added
to the two constructors, mimicking
```
public C()
{
Field1 = 0;
Field2 = Field1 + 1;
Field3 = 2;
}
```
and
```
public C()
{
Field1 = 0;
Field2 = Field1 + 1;
Field3 = 3;
}
```
respectively. This means that we no longer have to synthesize calls, callables,
parameters, and arguments in the data flow library, so much of the work from
d1755500e4 can be simplified.
Initial implementation of data flow through fields, using the algorithm of the
shared data flow implementation. Fields (and field-like properties) are covered,
and stores can be either
- ordinary assignments, `Foo = x`,
- object initializers, `new C() { Foo = x }`, or
- field initializers, `int Foo = x`.
For field initializers, we need to synthesize calls (`SynthesizedCall`),
callables (`SynthesizedCallable`), parameters (`InstanceParameterNode`), and
arguments (`SynthesizedThisArgumentNode`), as the C# extractor does not (yet)
extract such entities. For example, in
```
class C
{
int Field1 = 1;
int Field2 = 2;
C() { }
}
```
there is a synthesized call from the constructor `C`, with a synthesized `this`
argument, and the targets of that call are two synthesized callables with bodies
`this.Field1 = 1` and `this.Field2 = 2`, respectively.
A consequence of this is that `DataFlowCallable` is no longer an alias for
`DotNet::Callable`, but instead an IPA type.
