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Suggest impl Trait for References to Bare Trait in Function Header

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This commit is contained in:
Veera 2024-07-13 12:05:16 -04:00
parent 102997a939
commit 12de141df2
4 changed files with 92 additions and 52 deletions
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16
compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
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@ -4925,24 +4925,32 @@ impl<'v> Visitor<'v> for AwaitsVisitor {
}
}
/// Suggest a new type parameter name for diagnostic purposes.
///
/// `name` is the preferred name you'd like to suggest if it's not in use already.
pub trait NextTypeParamName {
fn next_type_param_name(&self, name: Option<&str>) -> String;
}
impl NextTypeParamName for &[hir::GenericParam<'_>] {
fn next_type_param_name(&self, name: Option<&str>) -> String {
// This is the list of possible parameter names that we might suggest.
// Type names are usually single letters in uppercase. So convert the first letter of input string to uppercase.
let name = name.and_then(|n| n.chars().next()).map(|c| c.to_uppercase().to_string());
let name = name.as_deref();
// This is the list of possible parameter names that we might suggest.
let possible_names = [name.unwrap_or("T"), "T", "U", "V", "X", "Y", "Z", "A", "B", "C"];
let used_names = self
// Filter out used names based on `filter_fn`.
let used_names: Vec<Symbol> = self
.iter()
.filter_map(|p| match p.name {
.filter_map(|param| match param.name {
hir::ParamName::Plain(ident) => Some(ident.name),
_ => None,
})
.collect::<Vec<_>>();
.collect();
// Find a name from `possible_names` that is not in `used_names`.
possible_names
.iter()
.find(|n| !used_names.contains(&Symbol::intern(n)))