fix: rewrite code_action `generate_delegate_trait`
I've made substantial enhancements to the "generate delegate trait" code action in rust-analyzer. Here's a summary of the changes:
#### Resolved the "Can’t find CONST_ARG@158..159 in AstIdMap" error
Fix#15804, fix#15968, fix#15108
The issue stemmed from an incorrect application of PathTransform in the original code. Previously, a new 'impl' was generated first and then transformed, causing PathTransform to fail in locating the correct AST node, resulting in an error. I rectified this by performing the transformation before generating the new 'impl' (using make::impl_trait), ensuring a step-by-step transformation of associated items.
#### Rectified generation of `Self` type
`generate_delegate_trait` is unable to properly handle trait with `Self` type.
Let's take the following code as an example:
```rust
trait Trait {
fn f() -> Self;
}
struct B {}
impl Trait for B {
fn f() -> B { B{} }
}
struct S {
b: B,
}
```
Here, if we implement `Trait` for `S`, the type of `f` should be `() -> Self`, i.e. `() -> S`. However we cannot automatically generate a function that constructs `S`.
To ensure that the code action doesn't generate delegate traits for traits with Self types, I add a function named `has_self_type` to handle it.
#### Extended support for generics in structs and fields within this code action
The former version of `generate_delegate_trait` cannot handle structs with generics properly. Here's an example:
```rust
struct B<T> {
a: T
}
trait Trait<T> {
fn f(a: T);
}
impl<T1, T2> Trait<T1> for B<T2> {
fn f(a: T1) -> T2 { self.a }
}
struct A {}
struct S {
b$0 : B<A>,
}
```
The former version will generates improper code:
```rust
impl<T1, T2> Trait<T1, T2> for S {
fn f(&self, a: T1) -> T1 {
<B as Trait<T1, T2>>::f( &self.b , a)
}
}
```
The rewritten version can handle generics properly:
```rust
impl<T1> Trait<T1> for S {
fn f(&self, a: T1) -> T1 {
<B<A> as Trait<T1>>::f(&self.b, a)
}
}
```
See more examples in added unit tests.
I enabled support for generic structs in `generate_delegate_trait` through the following steps (using the code example provided):
1. Initially, to prevent conflicts between the generic parameters in struct `S` and the ones in the impl of `B`, I renamed the generic parameters of `S`.
2. Then, since `B`'s parameters are instantiated within `S`, the original generic parameters of `B` needed removal within `S` (to avoid errors from redundant parameters). An important consideration here arises when Trait and B share parameters in `B`'s impl. In such cases, these shared generic parameters cannot be removed.
3. Next, I addressed the matching of types between `B`'s type in `S` and its type in the impl. Given that some generic parameters in the impl are instantiated in `B`, I replaced these parameters with their instantiated results using PathTransform. For instance, in the example provided, matching `B<A>` and `B<T2>`, where `T2` is instantiated as `A`, I replaced all occurrences of `T2` in the impl with `A` (i.e. apply the instantiated generic arguments to the params).
4. Finally, I performed transformations on each assoc item (also to prevent the initial issue) and handled redundant where clauses.
For a more detailed explanation, please refer to the code and comments. I welcome suggestions and any further questions!
fix: Don't emit "missing items" diagnostic for negative impls
Negative impls can't have items, so there is no reason for this diagnostic.
LMK if I should add a test somewhere. Also LMK if that's not how we usually check multiple things in an if in r-a.
TokenMap -> SpanMap rewrite
Opening early so I can have an overview over the full diff more easily, still very unfinished and lots of work to be done.
The gist of what this PR does is move away from assigning IDs to tokens in arguments and expansions and instead gives the subtrees the text ranges they are sourced from (made relative to some item for incrementality). This means we now only have a single map per expension, opposed to map for expansion and arguments.
A few of the things that are not done yet (in arbitrary order):
- [x] generally clean up the current mess
- [x] proc-macros, have been completely ignored so far
- [x] syntax fixups, has been commented out for the time being needs to be rewritten on top of some marker SyntaxContextId
- [x] macro invocation syntax contexts are not properly passed around yet, so $crate hygiene does not work in all cases (but most)
- [x] builtin macros do not set spans properly, $crate basically does not work with them rn (which we use)
~~- [ ] remove all uses of dummy spans (or if that does not work, change the dummy entries for dummy spans so that tests will not silently pass due to havin a file id for the dummy file)~~
- [x] de-queryfy `macro_expand`, the sole caller of it is `parse_macro_expansion`, and both of these are lru-cached with the same limit so having it be a query is pointless
- [x] docs and more docs
- [x] fix eager macro spans and other stuff
- [x] simplify include! handling
- [x] Figure out how to undo the sudden `()` expression wrapping in expansions / alternatively prioritize getting invisible delimiters working again
- [x] Simplify InFile stuff and HirFIleId extensions
~~- [ ] span crate containing all the file ids, span stuff, ast ids. Then remove the dependency injection generics from tt and mbe~~
Fixes https://github.com/rust-lang/rust-analyzer/issues/10300
Fixes https://github.com/rust-lang/rust-analyzer/issues/15685
fix: Diagnose everything in nested items, not just def diagnostics
Turns out we only calculated def diagnostics for these before (was wondering why I wasn't getting any type mismatches)
