7535: Extract function assist r=cpud36 a=cpud36
This PR adds `extract function/method` assist. closes#5409.
# Supported features
Assist should support extracting from expressions(`1`, `2 + 2`, `loop { }`) and from a series of statements, e.g.:
```rust
foo();
$0bar();
baz();$0
quix();
```
Assist also supports extracting parameters, like:
```rust
fn foo() -> i32 {
let n = 1;
$0n + 1$0
}
// -
fn foo() -> i32 {
let n = 1;
fun_name(n)
}
fn fun_name(n: i32) -> i32 {
n + 1
}
```
Extracting methods also generally works.
Assist allows referencing outer variables, both mutably and immutably, and handles handles access to variables local to extracted function:
```rust
fn foo() {
let mut n = 1;
let mut m = 2;
let mut moved_v = Vec::new();
let mut ref_mut_v = Vec::new();
$0
n += 1;
let k = 1;
moved_v.push(n);
let r = &mut m;
ref_mut_v.push(*r);
let h = 3;
$0
n = ref_mut_v.len() + k;
n -= h + m;
}
// -
fn foo() {
let mut n = 1;
let mut m = 2;
let mut moved_v = Vec::new();
let mut ref_mut_v = Vec::new();
let (k, h) = fun_name(&mut n, moved_v, &mut m, &mut ref_mut_v);
n = ref_mut_v.len() + k;
n -= h + m;
}
fn fun_name(n: &mut i32, mut moved_v: Vec<i32>, m: &mut i32, ref_mut_v: &mut Vec<i32>) -> (i32, i32) {
*n += 1;
let k = 1;
moved_v.push(*n);
let r = m;
ref_mut_v.push(*r);
let h = 3;
(k, h)
}
```
So we handle both input and output paramters
# Showcase
# Working with non-`Copy` types
Consider the following example:
```rust
fn foo() {
let v = Vec::new();
$0
let n = v.len();
$0
let is_empty = v.is_empty();
}
```
`v` must be a parameter to extracted function.
The question is, what type should it have.
It could be `v: Vec<i32>`, or `v: &Vec<i32>`.
The former is incorrect for `Vec<i32>`, but the later is silly for `i32`.
To resolve this we need to know if the type implements `Copy` trait.
I didn't find any api available from assists to query this.
`hir_ty::method_resolution::implements` seems relevant, but is isn't publicly re-exported from `hir`.
# Star(`*`) token and pointer dereference
If I understand correctly, in order to create expression like `*p`, one should use `ast::make::expr_prefix(T![*], ...)`, which
in turn calls `token(T![*])`.
`token` does not have star in `tokens::SOURCE_FILE`, so this panics.
I had to add `*` to `SOURCE_FILE` to make it work.
Correct me if this is not intended way to do this.
# Lowering access `value -> mut ref -> shared ref`
Consider the following example:
```rust
fn foo() {
let v = Vec::new();
$0 let n = v.len(); $0
}
```
`v` is not used after extracted function body, so both `v: &Vec<i32>` and `v: Vec<i32>` would work.
Currently the later would be chosen.
We can however check the body of extracted function and conclude that `v: &Vec<i32>` is sufficient.
Using `v: &Vec<i32>`(that is a minimal required access level) might be a better default.
I am unsure.
# Cleanup
The assist seems to be reasonably handling most of common cases.
If there are no concerns with code it produces(i.e. with test cases), I will start cleaning up
[edit]
added showcase
Co-authored-by: Vladyslav Katasonov <cpud47@gmail.com>
7541: Use block_def_map in body lowering (third time's the charm) r=jonas-schievink a=jonas-schievink
After https://github.com/rust-analyzer/rust-analyzer/pull/7380 and https://github.com/rust-analyzer/rust-analyzer/pull/7506 both had to be reverted, this should have finally resolved all remaining bugs.
Most importantly, the optimization to skip `block_def_map` computation when the block contains no inner items was fixed (which fortunately was simpler than expected).
I've ran `analysis-stats` on libstd locally, which works fine, and also ran this PR locally for a short while without issues.
Note that this *still* has no (or almost no) user-facing impact, because the rest of r-a still relies on some local item support hacks.
bors r+
Co-authored-by: Jonas Schievink <jonasschievink@gmail.com>
there are a few currently limitations:
* no modifications of function body
* does not handle mutability and references
* no method support
* may produce incorrect results
I've noticed that there are various suggestions that rust-analyzer seems
to filter out, even if they make sense.
Here's an example of where it seems like there should be a suggestion,
but there isn't:
It turns out that this specific suggestion is not considered
`MachineApplicable`, which are the only suggestions that rust-analyzer
accepts. However if you read the documentation for `MachineApplicable`,
b3897e3d13/compiler/rustc_lint_defs/src/lib.rs (L27-L29)
then you realize that these are specifically only those suggestions that
rust-analyzer could even automatically apply (in some distant future,
behind some setting or so). Other suggestions that may have some
semantic impact do not use `MachineApplicable`. So all other suggestions
are still intended to be suggested to the user, just not automatically
applied without the user being consulted.
b3897e3d13/compiler/rustc_lint_defs/src/lib.rs (L22-L24)
So with that in mind, rust-analyzer should almost definitely not filter
out `MaybeIncorrect` (which honestly is named horribly, it just means
that it's a semantic change, not just a syntactical one).
Then there's `HasPlaceholders` which basically is just another semantic
one, but with placeholders. The user will have to make some adjustments,
but the suggestion still is perfectly valid. rust-analyzer could
probably detect those placeholders and put proper "tab through" markers
there for the IDE, but that's not necessary for now.
Then the last one is `Unspecified` which is so unknown that I don't even
know how to judge it, meaning that the suggestion should probably also
just be suggested to the user and then they can decide.
So with all that in mind, I'm proposing to get rid of the check for
Applicability entirely.
