Improve syntax fixup for proc macros #12777
Labels
A-macro
macro expansion
C-feature
Category: feature request
E-easy
E-has-instructions
Issue has some instructions and pointers to code to get started
To make completion work inside attribute proc macros like
#[tokio::main]
, we take incomplete code inside the attribute input and 'fix it up' to make sure the proc macro can parse it. This already works pretty well in the common cases, but I think there are lots of edge cases missing. This usually results in completion not working inside the proc macro for a moment while typing something, and then working again once one has typed a more complete expression, so I think people are unlikely to report cases like this and will just chalk it up to "rust-analyzer being unreliable". So I think it's worth to look for edge cases that are missing and add them.Also, while it would be nice to have some more automatic / principled way to do this syntax fixup, any work adding more cases to the current code and extending the test suite will not be wasted; the test suite is really the most important part.
The syntax fixup code lives in the
fixup
module:rust-analyzer/crates/hir-expand/src/fixup.rs
Lines 1 to 3 in 96481b7
New cases will need to be added to the big
match_ast!
in thefixup_syntax
function:rust-analyzer/crates/hir-expand/src/fixup.rs
Line 73 in 96481b7
As can be seen from the existing cases, this mostly consists of checking if some part of a node is missing and inserting a simple placeholder token or two (an identifier, or some missing punctuation).
For each case, a test case should be added at the end of the module. The tests look like this:
rust-analyzer/crates/hir-expand/src/fixup.rs
Lines 288 to 300 in 96481b7
Test cases consist of the original incomplete code, and the "fixed up" code. The "fixed up" code can be automatically updated by running
UPDATE_EXPECT=1 cargo test -p hir-expand
, and the tests also check the important conditions that 1. the fixed-up code is syntactically complete, and 2. the fixups can be reversed afterwards, so if these checks succeed, the fixup is working.Here are some cases that I think we are missing currently:
foo::
loop
without a block,for
missing its various components etc.The text was updated successfully, but these errors were encountered: