At present, `var *;` is a crash because it has errors that weren't being properly stored/handled. This changes the handling to give more to track invalid parses in patterns.
`self` wasn't being handled in expression logic, only parameter logic. This is needed for `self.x`.
Also renames SelfDeducedParameter to SelfIdentifier because it's parsed fairly consistently with Identifier; this better represents the situations where `self` will need to be handled, it's where `Identifier` is allowed (although `Identifier` could also refer to a type... but I still think `SelfDeducedParameter` is a more difficult to understand name).
We could similarly add others -- this is intended to make it easy to add more that parse essentially the same.
The functionality expected is that types will use GetDeclarationContext in order to error on certain functionality in the declaration scope loop. e.g., with how constraints and interfaces currently don't allow definitions.
I've only moved out `package` because it's only valid on the top line. It might still be good to parse it later, but with slightly different logic because it would always be an error, and the declaration context isn't quite the right framing for that.
Also unifies some errors with `fn`.
Depends on #2646
Right now, deduced parameter handling is very narrow to `self` support. This folds it into pattern handling, which should eventually be a superset of deduced parameter support, so this will avoid more duplication of logic.
Note, this subtly adds handling of multiple deduced parameters, but not generic parameters (`:!`) so it's still not quite right.
The comments in parse_node_kind.def capture the change being made here.
Before:
```
// _external_: DeclaredName
// InterfaceBodyStart
// _external_: statements
// InterfaceBodyEnd
// InterfaceDefinition
```
After:
```
// InterfaceIntroducer
// DeclaredName
// InterfaceDefinitionStart
// _external_: declarations
// InterfaceDefinition
```
Really I just want to treat introduced things consistently. `var` defines my philosophy here: it doesn't always have a `DeclaredName`, so the `VarIntroducer` _must_ be the bounding node. By being consistent with that, I believe that overall the structure becomes easier to understand (that is, there are fewer inconsistencies to understand).
This also adds InterfaceDeclaration, since I think it can be predicted we'll have that, and it's helpful for making recover consistent with HandleDeclarationError.
Similarly, I'm also trying to standardize the loop processing a little with HandleDeclarationLoop. In the current approach, InterfaceDefinitionFinish isn't a necessary state, so I'm removing it.
Doing some sorting of functions / enums (generally speaking, I've been trying to keep these loosely lexically sorted for lack of a better ordering).
Also removes some code that seems to be dead, and a minor TODO comment fix.
- Finishes remaining "todo" parse nodes.
- Improving error recovery for invalid designators and structs, so that the parse tree still looks similar to a valid parse tree.
- Call expressions now have the thing being called as a child (of the start) instead of a sibling.
- Use of Start is replacing use of End in several parse nodes, like structs and call expressions.
- Adjusting documentation of parse node structures in an attempt to make it more consistent and understandable.
- The current state for interfaces and if/else is mostly being documented, not altered.
First change towards re-implementing interfaces using the new parser. I kept it small to make sure we are on the same page regarding stack states and how the parse tree should look like.
Co-authored-by: ergawy <kareem.ergawy@guardsquare.com>
Jon Ross-Perkins
Kareem Ergawy
