This is intended to be used for template instantiation, but for now takes no stance as to what it's cloning.
This is tested by parsing and cloning all of our test files, and checking that the result of converting each AST to proto is the same as the result of cloning and then converting each AST to proto.
Add a generic mechanism to decompose a `Value` and rebuild it, and use that to implement `Substitute`'s recursive transformation of values instead of a hand-rolled decomposition. This means `Substitute` now covers all kinds of values, whereas previously it used to be unable to transform some values, and should be less work to add new kinds of value.
We can use the same mechanism for various other things: structural dumping of values, equality comparisons, and value instantiation in the interpreter would all benefit from this. But in this change I'm just switching `Substitute` to this as a first step.
This does some more work to the run_clang_tidy.py wrapper script, and runs an example pass.
"again" because it's really the proto fuzzer changes that broke it, it had been working before.
"mostly" because there's still an issue within the proto fuzzer that it can't find "port/protobuf.h", i.e. https://github.com/google/libprotobuf-mutator/tree/master/port, but I'm still hesitant to add an include path there.
Change explorer's handling of witnesses to track them wherever possible. Associated constant support needs witnesses to be available much more pervasively.
The main changes here are:
- `Substitute` now takes a set of bindings covering both `Value`s for `GenericBinding`s and `Witness`es for `ImplBinding`s, and substitutes both.
- Witnesses are now tracked within `ConstraintType`s. The `.Self` type has an `ImplBinding` that self-references from parts of the constraint to other parts of the constraint can use to access the witness for the constraint.
- The constraint type for an `impl` and for a `GenericBinding` are now stored in pre-substituted form, with references to the actual constrained type rather than symbolic references to `.Self`. This results in minor changes in diagnostic text.
Argument deduction still performs substitutions without remapping witnesses.
Instead of forming a `SymbolicWitness` that contains an `Expression` when we can't directly resolve a witness to an `impl`, form different kinds of `Witness` values for the various situations:
- A `BindingWitness` witnesses that a type implements a constraint by reference to an `ImplBinding`.
- A `ConstraintWitness` witnesses that a type implements a constraint by reference to witnesses for each of the impl constraints within the constraint.
- A `ConstraintImplWitness` witnesses that a type implements a constraint by reference to a larger constraint which contains that constraint as an impl constraint.
Remove `SymbolicWitness` values and `InstantiateImpl` expressions, which are now unused. In order to remove the final usage of `SymbolicWitness`, I fixed a TODO to give `Self` the proper type within an interface declaration. I don't think this is an observable change.
No functional change intended.
This avoids the need to make copies of potentially large maps when
the same bindings are used in multiple values, such as when forming
a bound method value.
Richard Smith
Jon Ross-Perkins