diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src')
| -rw-r--r-- | compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs index 5c663e0bf4b..45e157b1080 100644 --- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs +++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs @@ -5023,24 +5023,32 @@ 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))) |