7147: ssr: Allow replacing expressions with statements r=davidlattimore a=MarijnS95
Depends on #6587
Until that is merged, the diff is https://github.com/MarijnS95/rust-analyzer/compare/stmt..replace-expr-with-stmt
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Now that statements can be matched and replaced (#6587) some usecases require expressions to be replaced with statements as well. This happens when something that can ambiguously be an expression or statement like `if` and loop blocks appear in the last position of a block, as trailing expression. In this case a replacement pattern of the form `if foo(){$a();}==>>$a();` will only substitute `if` blocks in the list of statements but not if they (implicitly) end up in the trailing expression, where they are not wrapped by an EXPR_STMT (but the pattern and template are, as parsing only succeeds for the `stmt ==>> stmt` case).
Instead of adding two rules that match an expression - and emit duplicate matching errors - allow the template for expressions to be a statement if it fails to parse as an expression.
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Another gross change that does not seem to break any tests currently, but perhaps a safeguard should be added to only allow this kind of replacement in blocks by "pushing" the replacement template to the statement list and clearing the trailing expression?
CC @davidlattimore
Co-authored-by: Marijn Suijten <marijn@traverseresearch.nl>
6587: SSR: Support statement matching and replacing r=davidlattimore a=MarijnS95
For #3186
Hi!
This is a smaller initial patchset that came up while working on support for statement lists (and my first time working on RA 😁). It has me stuck on trailing semicolons for which I hope to receive some feedback. Matching (and replacing) `let` bindings with a trailing semicolon works fine, but trying to omit these (to make patterns more ergonomic) turns out more complex than expected.
The "optional trailing semicolon solution" implemented in this PR is ugly because `Matcher::attempt_match_token` should only consume a trailing `;` when parsing `let` bindings to prevent other code from breaking. That at the same time has a nasty side-effect of `;` ending up in the matched code: any replacements on that should include the trailing semicolon as well even if it was not in the pattern. A better example is in the tests:
3ae1649c24/crates/ssr/src/tests.rs (L178-L184)
The end result to achieve is (I guess) allowing replacement of let bindings without trailing semicolon like `let x = $a ==>> let x = 1` (but including them on both sides is still fine), and should make replacement in a macro call (where `foo!(let a = 2;)` for a `$x:stmt` is invalid syntax) possible as well. That should allow to enable/fix these tests:
3ae1649c24/crates/ssr/src/tests.rs (L201-L214)
A possible MVP of this PR might be to drop this optional `;' handling entirely and only allow an SSR pattern/template with semicolons on either side.
Co-authored-by: Marijn Suijten <marijn@traverseresearch.nl>
Now that statements can be matched and replaced (#6587) some usecases
require expressions to be replaced with statements as well. This happens
when something that can ambiguously be an expression or statement like
`if` and loop blocks appear in the last position of a block, as trailing
expression. In this case a replacement pattern of the form `if
foo(){$a();}==>>$a();` will only substitute `if` blocks in the list of
statements but not if they (implicitly) end up in the trailing
expression, where they are not wrapped by an EXPR_STMT (but the pattern
and template are, as parsing only succeeds for the `stmt ==>> stmt`
case).
Instead of adding two rules that match an expression - and emit
duplicate matching errors - allow the template for expressions to be a
statement if it fails to parse as an expression.
We might want to provide more efficient impls for check if usages
exist, limiting the search, filtering and cancellation, so let's
violate YAGNI a bit here.
5758: SSR: Explicitly autoderef and ref placeholders as needed r=matklad a=davidlattimore
Structural search replace now inserts *, & and &mut in the replacement to match any auto[de]ref in the matched code.
e.g. `$a.foo() ==>> bar($a)` might convert `x.foo()` to `bar(&mut x)`
Co-authored-by: David Lattimore <dml@google.com>
