# Overview
Extracting a match arm value that has type unit into a function, when a
comma already follows the match arm value, results in an invalid (syntax
error) semicolon added between the newly generated function's generated
call and the comma.
# Example
Running this extraction
```rust
fn main() {
match () {
_ => $0()$0,
};
}
```
would lead to
```rust
fn main() {
match () {
_ => fun_name();,
};
}
fn fun_name() {
}
```
# Issue / Fix details
This happens because when there is no comma, rust-analyzer would simply
add the comma and wouldn't even try to evaluate whether it needs to add
a semicolon. But when the comma is there, it proceeds to evaluate
whether it needs to add a semicolon and it looks like the evaluation
logic erroneously ignores the possibility that we're in a match arm.
IIUC it never makes sense to add a semicolon when we're extracting from
a match arm value, so I've adjusted the logic to always decide against
adding a semicolon when we're in a match arm
Feat: extracted method from trait impl is placed in existing impl
**Before**
https://user-images.githubusercontent.com/1759192/183872883-3b0eafd2-d1dc-440e-9e66-38e3372f8b64.mp4
**After**
https://user-images.githubusercontent.com/1759192/183875769-87f34c7d-52f0-4dfc-9766-f591ee738ebb.mp4
Previously, when triggering a method extraction from within an impl trait block, then this would always create a new impl block for
the struct, even if there already is one. Now, if there is already an existing trait-less impl block, then it'll put the extracted method in there.
**Caveats**:
- It currently requires the target impl block to be non-empty. This limitation is because the current architecture takes a `node_to_insert_after` as reference for where to insert the extracted function. An empty impl block doesn't have such a reference node, since it's empty. It seems that supporting this requires a much larger and more complex change.
- This is my first contribution in rust, so apologies for any beginner mistakes.
Previously, when triggering a method extraction from within a trait
impl block, then this would always create a new impl block for
the struct, even if there already is one. Now, it'll put the extracted
method in the matching existing block if it exists.
This change attempts to resolve issue #7636: Extract into Function does not
create a generic function with constraints when extracting generic code.
In `FunctionBody::analyze_container`, we now traverse the `ancestors` in search
of `AnyHasGenericParams`, and attach any `GenericParamList`s and `WhereClause`s
we find to the `ContainerInfo`.
Later, in `format_function`, we collect all the `GenericParam`s and
`WherePred`s from the container, and filter them to keep only types matching
`TypeParam`s used within the newly extracted function body or param list. We
can then include the new `GenericParamList` and `WhereClause` in the new
function definition.
This change only impacts `TypeParam`s. `LifetimeParam`s and `ConstParam`s are
out of scope for this change.
This change fixes#12705.
In `FunctionBody::analyze`, we need to search any `ClosureExpr`s we encounter
for any `NameRef`s, to ensure they aren't missed.
fix: Extract function from trait impl
This change fixes#10036, "Extract to function assist implements nonexistent
trait methods".
When we detect that the extraction is coming from within a trait impl, and that
a `self` param will be necessary, we adjust which `SyntaxNode` to `insert_after`,
and create a new empty `impl` block for the newly extracted function.
