Merge #7572

7572: Add `find_or_create_impl_block` to assist utils r=matklad a=yoshuawuyts

This is another continuation of https://github.com/rust-analyzer/rust-analyzer/pull/7562, introducing a small util to either find an `impl` block, or create a new one if none exists. I copied this code from the `generate_new` assist into https://github.com/rust-analyzer/rust-analyzer/pull/7562, and this unifies both into a helper.

It doesn't feel super polished in its current state, but my hope is that this is enough of a starting point that it can be expanded on later. For example something that would be useful would be a flag which either returns the index of the start of the block, or the end of the block.

Anyway, I hope this is useful. Thanks!

Co-authored-by: Yoshua Wuyts <[email protected]>

1 files changed, 17 insertions, 1 deletions

diff --git a/crates/assists/src/utils.rs b/crates/assists/src/utils.rs
index 3842558d8..8045aac40 100644
--- a/crates/assists/src/utils.rs
+++ b/crates/assists/src/utils.rs
@@ -274,10 +274,11 @@ pub(crate) fn does_pat_match_variant(pat: &ast::Pat, var: &ast::Pat) -> bool {
 // Uses a syntax-driven approach to find any impl blocks for the struct that
 // exist within the module/file
 //
-// Returns `None` if we've found an existing `new` fn
+// Returns `None` if we've found an existing fn
 //
 // FIXME: change the new fn checking to a more semantic approach when that's more
 // viable (e.g. we process proc macros, etc)
+// FIXME: this partially overlaps with `find_impl_block`
 pub(crate) fn find_struct_impl(
     ctx: &AssistContext,
     strukt: &ast::AdtDef,
@@ -338,3 +339,18 @@ fn has_fn(imp: &ast::Impl, rhs_name: &str) -> bool {
 
     false
 }
+
+/// Find the start of the `impl` block for the given `ast::Impl`.
+//
+// FIXME: add a way to find the end of the `impl` block.
+// FIXME: this partially overlaps with `find_struct_impl`
+pub(crate) fn find_impl_block(impl_def: ast::Impl, buf: &mut String) -> Option<TextSize> {
+    buf.push('\n');
+    let start = impl_def
+        .syntax()
+        .descendants_with_tokens()
+        .find(|t| t.kind() == T!['{'])?
+        .text_range()
+        .end();
+    Some(start)
+}