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Improve test_unparenthesize to catch more false negatives #1787

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Merged
dtolnay merged 1 commit into from
Nov 29, 2024
Merged

Improve test_unparenthesize to catch more false negatives #1787

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50 changes: 46 additions & 4 deletions tests/test_unparenthesize.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ use std::panic;
use std::path::Path;
use std::sync::atomic::{AtomicUsize, Ordering};
use syn::visit_mut::{self, VisitMut};
use syn::Expr;
use syn::{Expr, Generics, LifetimeParam, TypeParam};

#[macro_use]
mod macros;
Expand Down Expand Up @@ -45,13 +45,55 @@ impl VisitMut for FlattenParens {
}
}

struct AsIfPrinted;

impl VisitMut for AsIfPrinted {
fn visit_generics_mut(&mut self, generics: &mut Generics) {
if generics.params.is_empty() {
generics.lt_token = None;
generics.gt_token = None;
}
if let Some(where_clause) = &generics.where_clause {
if where_clause.predicates.is_empty() {
generics.where_clause = None;
}
}
visit_mut::visit_generics_mut(self, generics);
}

fn visit_lifetime_param_mut(&mut self, param: &mut LifetimeParam) {
if param.bounds.is_empty() {
param.colon_token = None;
}
visit_mut::visit_lifetime_param_mut(self, param);
}

fn visit_type_param_mut(&mut self, param: &mut TypeParam) {
if param.bounds.is_empty() {
param.colon_token = None;
}
visit_mut::visit_type_param_mut(self, param);
}
}

fn test(path: &Path, failed: &AtomicUsize) {
let content = fs::read_to_string(path).unwrap();

match panic::catch_unwind(|| -> syn::Result<()> {
let mut syntax_tree = syn::parse_file(&content)?;
FlattenParens.visit_file_mut(&mut syntax_tree);
syn::parse2::<syn::File>(syntax_tree.to_token_stream())?;
let mut before = syn::parse_file(&content)?;
before.shebang = None;
FlattenParens.visit_file_mut(&mut before);
let printed = before.to_token_stream();
let mut after = syn::parse2::<syn::File>(printed.clone())?;
FlattenParens.visit_file_mut(&mut after);
// Normalize features that we expect Syn not to print.
AsIfPrinted.visit_file_mut(&mut before);
if before != after {
errorf!("=== {}\n", path.display());
if failed.fetch_add(1, Ordering::Relaxed) == 0 {
errorf!("BEFORE:\n{:#?}\nAFTER:\n{:#?}\n", before, after);
}
}
Ok(())
}) {
Err(_) => {
Expand Down