Suggestion to reorder generic parameters ignores type defaults

[varkor]

struct S<T = (), 'a>(&'a T);

results in:

error: lifetime parameters must be declared prior to type parameters
 --> src/lib.rs:1:18
  |
1 | struct S<T = (), 'a>(&'a T);
  |         ---------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T>`

when it should be:

help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = ()>`

This should be easy to fix: just replace ident in the following line with an appropriate format string.

rust/compiler/rustc_ast_passes/src/ast_validation.rs

Line 1157 in d107a87

GenericParamKind::Type { default: _ } => (ParamKindOrd::Type, ident),

[max-heller]

@rustbot claim

[max-heller]

This should be easy to fix: just replace ident in the following line with an appropriate format string.

rust/compiler/rustc_ast_passes/src/ast_validation.rs

Line 1157 in d107a87

GenericParamKind::Type { default: _ } => (ParamKindOrd::Type, ident),

For the record, it's not quite this simple, as doing so results in incorrect output when the parameter also has bounds. For example, it would render T: 'a = () as T = (): 'a because bounds are printed after the ident