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lifetimes lint: take "where" clauses into account (fixes #253)

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If a where clause is present and has lifetimes mentioned, just bail out.
This commit is contained in:
Georg Brandl 2015-08-30 09:57:52 +02:00
parent e340584cd8
commit 6461fb3308
2 changed files with 30 additions and 6 deletions
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30
src/lifetimes.rs
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@ -20,21 +20,21 @@ impl LintPass for LifetimePass {
fn check_item(&mut self, cx: &Context, item: &Item) {
if let ItemFn(ref decl, _, _, _, ref generics, _) = item.node {
check_fn_inner(cx, decl, None, &generics.lifetimes, item.span);
check_fn_inner(cx, decl, None, &generics, item.span);
}
}
fn check_impl_item(&mut self, cx: &Context, item: &ImplItem) {
if let MethodImplItem(ref sig, _) = item.node {
check_fn_inner(cx, &sig.decl, Some(&sig.explicit_self),
&sig.generics.lifetimes, item.span);
&sig.generics, item.span);
}
}
fn check_trait_item(&mut self, cx: &Context, item: &TraitItem) {
if let MethodTraitItem(ref sig, _) = item.node {
check_fn_inner(cx, &sig.decl, Some(&sig.explicit_self),
&sig.generics.lifetimes, item.span);
&sig.generics, item.span);
}
}
}
@ -49,11 +49,11 @@ enum RefLt {
use self::RefLt::*;
fn check_fn_inner(cx: &Context, decl: &FnDecl, slf: Option<&ExplicitSelf>,
named_lts: &[LifetimeDef], span: Span) {
if in_external_macro(cx, span) {
generics: &Generics, span: Span) {
if in_external_macro(cx, span) || has_where_lifetimes(&generics.where_clause) {
return;
}
if could_use_elision(decl, slf, named_lts) {
if could_use_elision(decl, slf, &generics.lifetimes) {
span_lint(cx, NEEDLESS_LIFETIMES, span,
"explicit lifetimes given in parameter types where they could be elided");
}
@ -182,3 +182,21 @@ impl<'v> Visitor<'v> for RefVisitor {
// for lifetime bounds; the default impl calls visit_lifetime_ref
fn visit_lifetime_bound(&mut self, _: &'v Lifetime) { }
}
/// Are any lifetimes mentioned in the `where` clause? If yes, we don't try to
/// reason about elision.
fn has_where_lifetimes(where_clause: &WhereClause) -> bool {
let mut where_visitor = RefVisitor(Vec::new());
for predicate in &where_clause.predicates {
match *predicate {
WherePredicate::RegionPredicate(..) => return true,
WherePredicate::BoundPredicate(ref pred) => {
walk_ty(&mut where_visitor, &pred.bounded_ty);
}
WherePredicate::EqPredicate(ref pred) => {
walk_ty(&mut where_visitor, &pred.ty);
}
}
}
!where_visitor.into_vec().is_empty()
}

6
tests/compile-fail/lifetimes.rs
View File

@ -31,6 +31,10 @@ fn deep_reference_2<'a>(x: Result<&'a u8, &'a u8>) -> &'a u8 { x.unwrap() } // n
fn deep_reference_3<'a>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> { Ok(x) }
//~^ERROR explicit lifetimes given
// where clause, but without lifetimes
fn where_clause_without_lt<'a, T>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> where T: Copy { Ok(x) }
//~^ERROR explicit lifetimes given
type Ref<'r> = &'r u8;
fn lifetime_param_1<'a>(_x: Ref<'a>, _y: &'a u8) { } // no error, same lifetime on two params
@ -40,6 +44,8 @@ fn lifetime_param_2<'a, 'b>(_x: Ref<'a>, _y: &'b u8) { }
fn lifetime_param_3<'a, 'b: 'a>(_x: Ref<'a>, _y: &'b u8) { } // no error, bounded lifetime
fn lifetime_param_4<'a, 'b>(_x: Ref<'a>, _y: &'b u8) where 'b: 'a { } // no error, bounded lifetime
struct X {
x: u8,
}