rust-clippy/src/ptr_arg.rs

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//! Checks for usage of &Vec[_] and &String
//!
//! This lint is **warn** by default
use rustc::lint::*;
use syntax::ast::*;
use rustc::middle::ty;
use utils::{span_lint, match_type};
use utils::{STRING_PATH, VEC_PATH};
declare_lint! {
pub PTR_ARG,
Allow,
"fn arguments of the type `&Vec<...>` or `&String`, suggesting to use `&[...]` or `&str` \
instead, respectively"
}
#[derive(Copy,Clone)]
pub struct PtrArg;
impl LintPass for PtrArg {
fn get_lints(&self) -> LintArray {
lint_array!(PTR_ARG)
}
fn check_item(&mut self, cx: &Context, item: &Item) {
if let &ItemFn(ref decl, _, _, _, _, _) = &item.node {
check_fn(cx, decl);
}
}
fn check_impl_item(&mut self, cx: &Context, item: &ImplItem) {
if let &MethodImplItem(ref sig, _) = &item.node {
check_fn(cx, &sig.decl);
}
}
fn check_trait_item(&mut self, cx: &Context, item: &TraitItem) {
if let &MethodTraitItem(ref sig, _) = &item.node {
check_fn(cx, &sig.decl);
}
}
}
fn check_fn(cx: &Context, decl: &FnDecl) {
for arg in &decl.inputs {
if let Some(pat_ty) = cx.tcx.pat_ty_opt(&arg.pat) {
if let ty::TyRef(_, ty::TypeAndMut { ty, mutbl: MutImmutable }) = pat_ty.sty {
if match_type(cx, ty, &VEC_PATH) {
span_lint(cx, PTR_ARG, arg.ty.span,
"writing `&Vec<_>` instead of `&[_]` involves one more reference \
and cannot be used with non-Vec-based slices. Consider changing \
the type to `&[...]`");
} else if match_type(cx, ty, &STRING_PATH) {
span_lint(cx, PTR_ARG, arg.ty.span,
"writing `&String` instead of `&str` involves a new object \
where a slice will do. Consider changing the type to `&str`");
}
}
}
}
}