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Merge pull request #957 from oli-obk/needs_borrow

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needless_borrow reported on &&T when only &T implements Trait and &Trait is required
This commit is contained in:
Martin Carton 2016-05-27 12:26:00 +02:00
commit ef46015151
2 changed files with 16 additions and 8 deletions
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17
src/needless_borrow.rs
View file

@ -3,9 +3,10 @@
//! This lint is **warn** by default
use rustc::lint::*;
use rustc::hir::*;
use rustc::hir::{ExprAddrOf, Expr, MutImmutable};
use rustc::ty::TyRef;
use utils::{span_lint, in_macro};
use rustc::ty::adjustment::AutoAdjustment::AdjustDerefRef;
/// **What it does:** This lint checks for address of operations (`&`) that are going to be dereferenced immediately by the compiler
///
@ -36,13 +37,13 @@ impl LateLintPass for NeedlessBorrow {
}
if let ExprAddrOf(MutImmutable, ref inner) = e.node {
if let TyRef(..) = cx.tcx.expr_ty(inner).sty {
let ty = cx.tcx.expr_ty(e);
let adj_ty = cx.tcx.expr_ty_adjusted(e);
if ty != adj_ty {
span_lint(cx,
NEEDLESS_BORROW,
e.span,
"this expression borrows a reference that is immediately dereferenced by the compiler");
if let Some(&AdjustDerefRef(ref deref)) = cx.tcx.tables.borrow().adjustments.get(&e.id) {
if deref.autoderefs > 1 && deref.autoref.is_some() {
span_lint(cx,
NEEDLESS_BORROW,
e.span,
"this expression borrows a reference that is immediately dereferenced by the compiler");
}
}
}
}

7
tests/compile-fail/needless_borrow.rs
View file

@ -16,6 +16,7 @@ fn main() {
let g_val = g(&Vec::new()); // should not error, because `&Vec<T>` derefs to `&[T]`
let vec = Vec::new();
let vec_val = g(&vec); // should not error, because `&Vec<T>` derefs to `&[T]`
h(&"foo"); // should not error, because the `&&str` is required, due to `&Trait`
}
fn f<T:Copy>(y: &T) -> T {
@ -25,3 +26,9 @@ fn f<T:Copy>(y: &T) -> T {
fn g(y: &[u8]) -> u8 {
y[0]
}
trait Trait {}
impl<'a> Trait for &'a str {}
fn h(_: &Trait) {}