parent_substs: &[subst::GenericArg<'tcx>],
has_self: bool,
self_ty: Option<Ty<'tcx>>,
+ arg_count_mismatch: bool,
args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs<'b>>, bool),
provided_kind: impl Fn(&GenericParamDef, &GenericArg<'_>) -> subst::GenericArg<'tcx>,
mut inferred_kind: impl FnMut(
// methods in `subst.rs`, so that we can iterate over the arguments and
// parameters in lock-step linearly, instead of trying to match each pair.
let mut substs: SmallVec<[subst::GenericArg<'tcx>; 8]> = SmallVec::with_capacity(count);
-
// Iterate over each segment of the path.
while let Some((def_id, defs)) = stack.pop() {
let mut params = defs.params.iter().peekable();
let mut args =
generic_args.iter().flat_map(|generic_args| generic_args.args.iter()).peekable();
+ let arg_kind = |arg| match arg {
+ &GenericArg::Lifetime(_) => "lifetime",
+ &GenericArg::Type(_) => "type",
+ &GenericArg::Const(_) => "constant",
+ };
+
+ // If we encounter a type or const when we expect a lifetime, we infer the lifetimes.
+ // If we later encounter a lifetime, we know that the arguments were provided in the
+ // wrong order. `force_infer_lt` records the type or const that forced lifetimes to be
+ // inferred, so we can use it for diagnostics later.
+ let mut force_infer_lt = None;
+
loop {
// We're going to iterate through the generic arguments that the user
// provided, matching them with the generic parameters we expect.
// We expected a lifetime argument, but got a type or const
// argument. That means we're inferring the lifetimes.
substs.push(inferred_kind(None, param, infer_args));
+ force_infer_lt = Some(arg);
params.next();
}
- (_, _) => {
+ (_, kind) => {
// We expected one kind of parameter, but the user provided
- // another. This is an error, but we need to handle it
- // gracefully so we can report sensible errors.
- // In this case, we're simply going to infer this argument.
- args.next();
+ // another. This is an error. However, if we already know that
+ // the arguments don't match up with the parameters, we won't issue
+ // an additional error, as the user already knows what's wrong.
+ if !arg_count_mismatch {
+ let param_kind = match kind {
+ GenericParamDefKind::Lifetime => "lifetime",
+ GenericParamDefKind::Type { .. } => "type",
+ GenericParamDefKind::Const => "constant",
+ };
+ struct_span_err!(
+ tcx.sess,
+ arg.span(),
+ E0747,
+ "{} provided when a {} was expected",
+ arg_kind(arg),
+ param_kind,
+ )
+ .emit();
+ }
+
+ // We've reported the error, but we want to make sure that this
+ // problem doesn't bubble down and create additional, irrelevant
+ // errors. In this case, we're simply going to ignore the argument
+ // and any following arguments. The rest of the parameters will be
+ // inferred.
+ while args.next().is_some() {}
}
}
}
- (Some(_), None) => {
+ (Some(&arg), None) => {
// We should never be able to reach this point with well-formed input.
- // Getting to this point means the user supplied more arguments than
- // there are parameters.
- args.next();
+ // There are two situations in which we can encounter this issue.
+ //
+ // 1. The number of arguments is incorrect. In this case, an error
+ // will already have been emitted, and we can ignore it. This case
+ // also occurs when late-bound lifetime parameters are present, yet
+ // the lifetime arguments have also been explicitly specified by the
+ // user.
+ // 2. We've inferred some lifetimes, which have been provided later (i.e.
+ // after a type or const). We want to throw an error in this case.
+
+ if !arg_count_mismatch {
+ let kind = arg_kind(arg);
+ assert_eq!(kind, "lifetime");
+ let provided =
+ force_infer_lt.expect("lifetimes ought to have been inferred");
+ struct_span_err!(
+ tcx.sess,
+ provided.span(),
+ E0747,
+ "{} provided when a {} was expected",
+ arg_kind(provided),
+ kind,
+ )
+ .emit();
+ }
+
+ break;
}
(None, Some(¶m)) => {
// If there are fewer arguments than parameters, it means
// we're inferring the remaining arguments.
substs.push(inferred_kind(Some(&substs), param, infer_args));
- args.next();
params.next();
}
(None, None) => break,
assert!(self_ty.is_none() && parent_substs.is_empty());
}
- let (_, potential_assoc_types) = Self::check_generic_arg_count(
+ let (arg_count_mismatch, potential_assoc_types) = Self::check_generic_arg_count(
tcx,
span,
&generic_params,
parent_substs,
self_ty.is_some(),
self_ty,
+ arg_count_mismatch,
// Provide the generic args, and whether types should be inferred.
|did| {
if did == def_id {
projects / rust.git / blobdiff