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issue#3318 run trivially_copy_pass_by_ref for traits

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This commit is contained in:
Wayne Warren 2018-11-20 18:49:15 -06:00
parent 67c32eb2c4
commit 92f7f9061c
1 changed files with 93 additions and 41 deletions
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134
clippy_lints/src/trivially_copy_pass_by_ref.rs
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@ -18,12 +18,13 @@ use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use crate::rustc::{declare_tool_lint, lint_array};
use if_chain::if_chain;
use crate::rustc::ty::TyKind;
use crate::rustc::ty::FnSig;
use crate::rustc::session::config::Config as SessionConfig;
use crate::rustc_target::spec::abi::Abi;
use crate::rustc_target::abi::LayoutOf;
use crate::syntax::ast::NodeId;
use crate::syntax_pos::Span;
use crate::utils::{in_macro, is_copy, is_self, span_lint_and_sugg, snippet};
use crate::utils::{in_macro, is_copy, is_self_ty, span_lint_and_sugg, snippet};
/// **What it does:** Checks for functions taking arguments by reference, where
/// the argument type is `Copy` and small enough to be more efficient to always
@ -67,7 +68,7 @@ pub struct TriviallyCopyPassByRef {
limit: u64,
}
impl TriviallyCopyPassByRef {
impl<'a, 'tcx> TriviallyCopyPassByRef {
pub fn new(limit: Option<u64>, target: &SessionConfig) -> Self {
let limit = limit.unwrap_or_else(|| {
let bit_width = target.usize_ty.bit_width().expect("usize should have a width") as u64;
@ -80,6 +81,84 @@ impl TriviallyCopyPassByRef {
});
Self { limit }
}
fn check_trait_method(
&mut self,
cx: &LateContext<'_, 'tcx>,
item: &TraitItemRef
) {
let method_def_id = cx.tcx.hir.local_def_id(item.id.node_id);
let method_sig = cx.tcx.fn_sig(method_def_id);
let method_sig = cx.tcx.erase_late_bound_regions(&method_sig);
let decl = match cx.tcx.hir.fn_decl(item.id.node_id) {
Some(b) => b,
None => return,
};
self.check_poly_fn(cx, &decl, &method_sig, None);
}
fn check_poly_fn(
&mut self,
cx: &LateContext<'_, 'tcx>,
decl: &FnDecl,
sig: &FnSig<'tcx>,
span: Option<Span>,
) {
// Use lifetimes to determine if we're returning a reference to the
// argument. In that case we can't switch to pass-by-value as the
// argument will not live long enough.
let output_lts = match sig.output().sty {
TyKind::Ref(output_lt, _, _) => vec![output_lt],
TyKind::Adt(_, substs) => substs.regions().collect(),
_ => vec![],
};
for (input, &ty) in decl.inputs.iter().zip(sig.inputs()) {
// All spans generated from a proc-macro invocation are the same...
match span {
Some(s) if s == input.span => return,
_ => (),
}
if_chain! {
if let TyKind::Ref(input_lt, ty, Mutability::MutImmutable) = ty.sty;
if !output_lts.contains(&input_lt);
if is_copy(cx, ty);
if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes());
if size <= self.limit;
if let hir::TyKind::Rptr(_, MutTy { ty: ref decl_ty, .. }) = input.node;
then {
let value_type = if is_self_ty(decl_ty) {
"self".into()
} else {
snippet(cx, decl_ty.span, "_").into()
};
span_lint_and_sugg(
cx,
TRIVIALLY_COPY_PASS_BY_REF,
input.span,
"this argument is passed by reference, but would be more efficient if passed by value",
"consider passing by value instead",
value_type);
}
}
}
}
fn check_trait_items(
&mut self,
cx: &LateContext<'_, '_>,
trait_items: &[TraitItemRef]
) {
for item in trait_items {
match item.kind {
AssociatedItemKind::Method{ has_self: _ } => self.check_trait_method(cx, item),
_ => (),
}
}
}
}
impl LintPass for TriviallyCopyPassByRef {
@ -89,12 +168,22 @@ impl LintPass for TriviallyCopyPassByRef {
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TriviallyCopyPassByRef {
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
if in_macro(item.span) {
return;
}
match item.node {
ItemKind::Trait(_, _, _, _, ref trait_items) => self.check_trait_items(cx, trait_items),
_ => (),
}
}
fn check_fn(
&mut self,
cx: &LateContext<'a, 'tcx>,
kind: FnKind<'tcx>,
decl: &'tcx FnDecl,
body: &'tcx Body,
_body: &'tcx Body,
span: Span,
node_id: NodeId,
) {
@ -131,43 +220,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TriviallyCopyPassByRef {
let fn_sig = cx.tcx.fn_sig(fn_def_id);
let fn_sig = cx.tcx.erase_late_bound_regions(&fn_sig);
// Use lifetimes to determine if we're returning a reference to the
// argument. In that case we can't switch to pass-by-value as the
// argument will not live long enough.
let output_lts = match fn_sig.output().sty {
TyKind::Ref(output_lt, _, _) => vec![output_lt],
TyKind::Adt(_, substs) => substs.regions().collect(),
_ => vec![],
};
for ((input, &ty), arg) in decl.inputs.iter().zip(fn_sig.inputs()).zip(&body.arguments) {
// All spans generated from a proc-macro invocation are the same...
if span == input.span {
return;
}
if_chain! {
if let TyKind::Ref(input_lt, ty, Mutability::MutImmutable) = ty.sty;
if !output_lts.contains(&input_lt);
if is_copy(cx, ty);
if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes());
if size <= self.limit;
if let hir::TyKind::Rptr(_, MutTy { ty: ref decl_ty, .. }) = input.node;
then {
let value_type = if is_self(arg) {
"self".into()
} else {
snippet(cx, decl_ty.span, "_").into()
};
span_lint_and_sugg(
cx,
TRIVIALLY_COPY_PASS_BY_REF,
input.span,
"this argument is passed by reference, but would be more efficient if passed by value",
"consider passing by value instead",
value_type);
}
}
}
self.check_poly_fn(cx, decl, &fn_sig, Some(span));
}
}