rustc: buffer the output writer for -Z ast-json[-noexpand]. #12999
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
rustc: buffer the output writer for -Z ast-json[-noexpand].
This takes the time for
rustc libstd/lib.rs -Z ast-json-noexpand > file.json
from 9.0s to 3.5s (~0.5s spent parsing etc.) and-Z ast-json
from 11s to 5s (~1.5s spent parsing and expanding).