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Add large_types_passed_by_value lint

Browse source 
Refactor trivially_copy_pass_by_ref and the new lint into pass_by_ref_or_value module

Update stderr of conf_unknown_key test

Rename lint to large_types_passed_by_value

Increase `pass_by_value_size_limit` default value to 256

Improve rules for `large_types_passed_by_value`

Improve tests for `large_types_passed_by_value`

Improve documentation for `large_types_passed_by_value`

Make minor corrections to pass_by_ref_or_value.rs suggested by clippy itself

Fix `large_types_passed_by_value` example and improve docs

pass_by_ref_or_value: Tweak check for mut annotation in params

large_types_passed_by_value: add tests for pub trait, trait impl and inline attributes
This commit is contained in:
Cauê Baasch de Souza 2020-10-08 02:17:32 -03:00
parent bf1c6f9871
commit e8731a926c
9 changed files with 394 additions and 190 deletions
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1
CHANGELOG.md
View file

@ -1779,6 +1779,7 @@ Released 2018-09-13
[`large_digit_groups`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_digit_groups
[`large_enum_variant`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_enum_variant
[`large_stack_arrays`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_stack_arrays
[`large_types_passed_by_value`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_types_passed_by_value
[`len_without_is_empty`]: https://rust-lang.github.io/rust-clippy/master/index.html#len_without_is_empty
[`len_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#len_zero
[`let_and_return`]: https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return

13
clippy_lints/src/lib.rs
View file

@ -278,6 +278,7 @@ mod overflow_check_conditional;
mod panic_in_result_fn;
mod panic_unimplemented;
mod partialeq_ne_impl;
mod pass_by_ref_or_value;
mod path_buf_push_overwrite;
mod pattern_type_mismatch;
mod precedence;
@ -311,7 +312,6 @@ mod to_string_in_display;
mod trait_bounds;
mod transmute;
mod transmuting_null;
mod trivially_copy_pass_by_ref;
mod try_err;
mod types;
mod unicode;
@ -776,6 +776,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
&panic_unimplemented::UNIMPLEMENTED,
&panic_unimplemented::UNREACHABLE,
&partialeq_ne_impl::PARTIALEQ_NE_IMPL,
&pass_by_ref_or_value::LARGE_TYPES_PASSED_BY_VALUE,
&pass_by_ref_or_value::TRIVIALLY_COPY_PASS_BY_REF,
&path_buf_push_overwrite::PATH_BUF_PUSH_OVERWRITE,
&pattern_type_mismatch::PATTERN_TYPE_MISMATCH,
&precedence::PRECEDENCE,
@ -835,7 +837,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
&transmute::USELESS_TRANSMUTE,
&transmute::WRONG_TRANSMUTE,
&transmuting_null::TRANSMUTING_NULL,
&trivially_copy_pass_by_ref::TRIVIALLY_COPY_PASS_BY_REF,
&try_err::TRY_ERR,
&types::ABSURD_EXTREME_COMPARISONS,
&types::BORROWED_BOX,
@ -1009,11 +1010,12 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(move || box large_enum_variant::LargeEnumVariant::new(enum_variant_size_threshold));
store.register_late_pass(|| box explicit_write::ExplicitWrite);
store.register_late_pass(|| box needless_pass_by_value::NeedlessPassByValue);
let trivially_copy_pass_by_ref = trivially_copy_pass_by_ref::TriviallyCopyPassByRef::new(
let pass_by_ref_or_value = pass_by_ref_or_value::PassByRefOrValue::new(
conf.trivial_copy_size_limit,
conf.pass_by_value_size_limit,
&sess.target,
);
store.register_late_pass(move || box trivially_copy_pass_by_ref);
store.register_late_pass(move || box pass_by_ref_or_value);
store.register_late_pass(|| box try_err::TryErr);
store.register_late_pass(|| box use_self::UseSelf);
store.register_late_pass(|| box bytecount::ByteCount);
@ -1237,13 +1239,14 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&needless_pass_by_value::NEEDLESS_PASS_BY_VALUE),
LintId::of(&non_expressive_names::SIMILAR_NAMES),
LintId::of(&option_if_let_else::OPTION_IF_LET_ELSE),
LintId::of(&pass_by_ref_or_value::LARGE_TYPES_PASSED_BY_VALUE),
LintId::of(&pass_by_ref_or_value::TRIVIALLY_COPY_PASS_BY_REF),
LintId::of(&ranges::RANGE_MINUS_ONE),
LintId::of(&ranges::RANGE_PLUS_ONE),
LintId::of(&shadow::SHADOW_UNRELATED),
LintId::of(&strings::STRING_ADD_ASSIGN),
LintId::of(&trait_bounds::TRAIT_DUPLICATION_IN_BOUNDS),
LintId::of(&trait_bounds::TYPE_REPETITION_IN_BOUNDS),
LintId::of(&trivially_copy_pass_by_ref::TRIVIALLY_COPY_PASS_BY_REF),
LintId::of(&types::CAST_LOSSLESS),
LintId::of(&types::CAST_POSSIBLE_TRUNCATION),
LintId::of(&types::CAST_POSSIBLE_WRAP),

256
clippy_lints/src/pass_by_ref_or_value.rs Normal file
View file

@ -0,0 +1,256 @@
use std::cmp;
use crate::utils::{is_copy, is_self_ty, snippet, span_lint_and_sugg};
use if_chain::if_chain;
use rustc_ast::attr;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::intravisit::FnKind;
use rustc_hir::{BindingAnnotation, Body, FnDecl, HirId, ItemKind, MutTy, Mutability, Node, PatKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::Span;
use rustc_target::abi::LayoutOf;
use rustc_target::spec::abi::Abi;
use rustc_target::spec::Target;
declare_clippy_lint! {
/// **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
/// pass by value.
///
/// **Why is this bad?** In many calling conventions instances of structs will
/// be passed through registers if they fit into two or less general purpose
/// registers.
///
/// **Known problems:** This lint is target register size dependent, it is
/// limited to 32-bit to try and reduce portability problems between 32 and
/// 64-bit, but if you are compiling for 8 or 16-bit targets then the limit
/// will be different.
///
/// The configuration option `trivial_copy_size_limit` can be set to override
/// this limit for a project.
///
/// This lint attempts to allow passing arguments by reference if a reference
/// to that argument is returned. This is implemented by comparing the lifetime
/// of the argument and return value for equality. However, this can cause
/// false positives in cases involving multiple lifetimes that are bounded by
/// each other.
///
/// **Example:**
///
/// ```rust
/// // Bad
/// fn foo(v: &u32) {}
/// ```
///
/// ```rust
/// // Better
/// fn foo(v: u32) {}
/// ```
pub TRIVIALLY_COPY_PASS_BY_REF,
pedantic,
"functions taking small copyable arguments by reference"
}
declare_clippy_lint! {
/// **What it does:** Checks for functions taking arguments by value, where
/// the argument type is `Copy` and large enough to be worth considering
/// passing by reference. Does not trigger if the function is being exported,
/// because that might induce API breakage, if the parameter is declared as mutable,
/// or if the argument is a `self`.
///
/// **Why is this bad?** Arguments passed by value might result in an unnecessary
/// shallow copy, taking up more space in the stack and requiring a call to
/// `memcpy`, which which can be expensive.
///
/// **Example:**
///
/// ```rust
/// #[derive(Clone, Copy)]
/// struct TooLarge([u8; 2048]);
///
/// // Bad
/// fn foo(v: TooLarge) {}
/// ```
/// ```rust
/// #[derive(Clone, Copy)]
/// struct TooLarge([u8; 2048]);
///
/// // Good
/// fn foo(v: &TooLarge) {}
/// ```
pub LARGE_TYPES_PASSED_BY_VALUE,
pedantic,
"functions taking large arguments by value"
}
#[derive(Copy, Clone)]
pub struct PassByRefOrValue {
ref_min_size: u64,
value_max_size: u64,
}
impl<'tcx> PassByRefOrValue {
pub fn new(ref_min_size: Option<u64>, value_max_size: u64, target: &Target) -> Self {
let ref_min_size = ref_min_size.unwrap_or_else(|| {
let bit_width = u64::from(target.pointer_width);
// Cap the calculated bit width at 32-bits to reduce
// portability problems between 32 and 64-bit targets
let bit_width = cmp::min(bit_width, 32);
#[allow(clippy::integer_division)]
let byte_width = bit_width / 8;
// Use a limit of 2 times the register byte width
byte_width * 2
});
Self {
ref_min_size,
value_max_size,
}
}
fn check_poly_fn(&mut self, cx: &LateContext<'tcx>, hir_id: HirId, decl: &FnDecl<'_>, span: Option<Span>) {
let fn_def_id = cx.tcx.hir().local_def_id(hir_id);
let fn_sig = cx.tcx.fn_sig(fn_def_id);
let fn_sig = cx.tcx.erase_late_bound_regions(&fn_sig);
let fn_body = cx.enclosing_body.map(|id| cx.tcx.hir().body(id));
for (index, (input, &ty)) in decl.inputs.iter().zip(fn_sig.inputs()).enumerate() {
// All spans generated from a proc-macro invocation are the same...
match span {
Some(s) if s == input.span => return,
_ => (),
}
match ty.kind() {
ty::Ref(input_lt, ty, Mutability::Not) => {
// 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().kind() {
ty::Ref(output_lt, _, _) => vec![output_lt],
ty::Adt(_, substs) => substs.regions().collect(),
_ => vec![],
};
if_chain! {
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.ref_min_size;
if let hir::TyKind::Rptr(_, MutTy { ty: ref decl_ty, .. }) = input.kind;
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,
&format!("this argument ({} byte) is passed by reference, but would be more efficient if passed by value (limit: {} byte)", size, self.ref_min_size),
"consider passing by value instead",
value_type,
Applicability::Unspecified,
);
}
}
},
ty::Adt(_, _) | ty::Array(_, _) | ty::Tuple(_) => {
// if function has a body and parameter is annotated with mut, ignore
if let Some(param) = fn_body.and_then(|body| body.params.get(index)) {
match param.pat.kind {
PatKind::Binding(BindingAnnotation::Unannotated, _, _, _) => {},
_ => continue,
}
}
if_chain! {
if !cx.access_levels.is_exported(hir_id);
if is_copy(cx, ty);
if !is_self_ty(input);
if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes());
if size > self.value_max_size;
then {
span_lint_and_sugg(
cx,
LARGE_TYPES_PASSED_BY_VALUE,
input.span,
&format!("this argument ({} byte) is passed by value, but might be more efficient if passed by reference (limit: {} byte)", size, self.value_max_size),
"consider passing by reference instead",
format!("&{}", snippet(cx, input.span, "_")),
Applicability::MaybeIncorrect,
);
}
}
},
_ => {},
}
}
}
}
impl_lint_pass!(PassByRefOrValue => [TRIVIALLY_COPY_PASS_BY_REF, LARGE_TYPES_PASSED_BY_VALUE]);
impl<'tcx> LateLintPass<'tcx> for PassByRefOrValue {
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
if item.span.from_expansion() {
return;
}
if let hir::TraitItemKind::Fn(method_sig, _) = &item.kind {
self.check_poly_fn(cx, item.hir_id, &*method_sig.decl, None);
}
}
fn check_fn(
&mut self,
cx: &LateContext<'tcx>,
kind: FnKind<'tcx>,
decl: &'tcx FnDecl<'_>,
_body: &'tcx Body<'_>,
span: Span,
hir_id: HirId,
) {
if span.from_expansion() {
return;
}
match kind {
FnKind::ItemFn(.., header, _, attrs) => {
if header.abi != Abi::Rust {
return;
}
for a in attrs {
if let Some(meta_items) = a.meta_item_list() {
if a.has_name(sym!(proc_macro_derive))
|| (a.has_name(sym!(inline)) && attr::list_contains_name(&meta_items, sym!(always)))
{
return;
}
}
}
},
FnKind::Method(..) => (),
FnKind::Closure(..) => return,
}
// Exclude non-inherent impls
if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) {
if matches!(item.kind, ItemKind::Impl{ of_trait: Some(_), .. } |
ItemKind::Trait(..))
{
return;
}
}
self.check_poly_fn(cx, hir_id, decl, Some(span));
}
}

183
clippy_lints/src/trivially_copy_pass_by_ref.rs
View file

@ -1,183 +0,0 @@
use std::cmp;
use crate::utils::{is_copy, is_self_ty, snippet, span_lint_and_sugg};
use if_chain::if_chain;
use rustc_ast::attr;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::intravisit::FnKind;
use rustc_hir::{Body, FnDecl, HirId, ItemKind, MutTy, Mutability, Node};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::Span;
use rustc_target::abi::LayoutOf;
use rustc_target::spec::abi::Abi;
use rustc_target::spec::Target;
declare_clippy_lint! {
/// **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
/// pass by value.
///
/// **Why is this bad?** In many calling conventions instances of structs will
/// be passed through registers if they fit into two or less general purpose
/// registers.
///
/// **Known problems:** This lint is target register size dependent, it is
/// limited to 32-bit to try and reduce portability problems between 32 and
/// 64-bit, but if you are compiling for 8 or 16-bit targets then the limit
/// will be different.
///
/// The configuration option `trivial_copy_size_limit` can be set to override
/// this limit for a project.
///
/// This lint attempts to allow passing arguments by reference if a reference
/// to that argument is returned. This is implemented by comparing the lifetime
/// of the argument and return value for equality. However, this can cause
/// false positives in cases involving multiple lifetimes that are bounded by
/// each other.
///
/// **Example:**
///
/// ```rust
/// // Bad
/// fn foo(v: &u32) {}
/// ```
///
/// ```rust
/// // Better
/// fn foo(v: u32) {}
/// ```
pub TRIVIALLY_COPY_PASS_BY_REF,
pedantic,
"functions taking small copyable arguments by reference"
}
#[derive(Copy, Clone)]
pub struct TriviallyCopyPassByRef {
limit: u64,
}
impl<'tcx> TriviallyCopyPassByRef {
pub fn new(limit: Option<u64>, target: &Target) -> Self {
let limit = limit.unwrap_or_else(|| {
let bit_width = u64::from(target.pointer_width);
// Cap the calculated bit width at 32-bits to reduce
// portability problems between 32 and 64-bit targets
let bit_width = cmp::min(bit_width, 32);
#[allow(clippy::integer_division)]
let byte_width = bit_width / 8;
// Use a limit of 2 times the register byte width
byte_width * 2
});
Self { limit }
}
fn check_poly_fn(&mut self, cx: &LateContext<'tcx>, hir_id: HirId, decl: &FnDecl<'_>, span: Option<Span>) {
let fn_def_id = cx.tcx.hir().local_def_id(hir_id);
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().kind() {
ty::Ref(output_lt, _, _) => vec![output_lt],
ty::Adt(_, substs) => substs.regions().collect(),
_ => vec![],
};
for (input, &ty) in decl.inputs.iter().zip(fn_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 ty::Ref(input_lt, ty, Mutability::Not) = ty.kind();
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.kind;
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,
&format!("this argument ({} byte) is passed by reference, but would be more efficient if passed by value (limit: {} byte)", size, self.limit),
"consider passing by value instead",
value_type,
Applicability::Unspecified,
);
}
}
}
}
}
impl_lint_pass!(TriviallyCopyPassByRef => [TRIVIALLY_COPY_PASS_BY_REF]);
impl<'tcx> LateLintPass<'tcx> for TriviallyCopyPassByRef {
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
if item.span.from_expansion() {
return;
}
if let hir::TraitItemKind::Fn(method_sig, _) = &item.kind {
self.check_poly_fn(cx, item.hir_id, &*method_sig.decl, None);
}
}
fn check_fn(
&mut self,
cx: &LateContext<'tcx>,
kind: FnKind<'tcx>,
decl: &'tcx FnDecl<'_>,
_body: &'tcx Body<'_>,
span: Span,
hir_id: HirId,
) {
if span.from_expansion() {
return;
}
match kind {
FnKind::ItemFn(.., header, _, attrs) => {
if header.abi != Abi::Rust {
return;
}
for a in attrs {
if let Some(meta_items) = a.meta_item_list() {
if a.has_name(sym!(proc_macro_derive))
|| (a.has_name(sym!(inline)) && attr::list_contains_name(&meta_items, sym!(always)))
{
return;
}
}
}
},
FnKind::Method(..) => (),
FnKind::Closure(..) => return,
}
// Exclude non-inherent impls
if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) {
if matches!(item.kind, ItemKind::Impl{ of_trait: Some(_), .. } |
ItemKind::Trait(..))
{
return;
}
}
self.check_poly_fn(cx, hir_id, decl, Some(span));
}
}

2
clippy_lints/src/utils/conf.rs
View file

@ -150,6 +150,8 @@ define_Conf! {
(literal_representation_threshold, "literal_representation_threshold": u64, 16384),
/// Lint: TRIVIALLY_COPY_PASS_BY_REF. The maximum size (in bytes) to consider a `Copy` type for passing by value instead of by reference.
(trivial_copy_size_limit, "trivial_copy_size_limit": Option<u64>, None),
/// Lint: LARGE_TYPE_PASS_BY_MOVE. The minimum size (in bytes) to consider a type for passing by reference instead of by value.
(pass_by_value_size_limit, "pass_by_value_size_limit": u64, 256),
/// Lint: TOO_MANY_LINES. The maximum number of lines a function or method can have
(too_many_lines_threshold, "too_many_lines_threshold": u64, 100),
/// Lint: LARGE_STACK_ARRAYS, LARGE_CONST_ARRAYS. The maximum allowed size for arrays on the stack

9
src/lintlist/mod.rs
View file

@ -1061,6 +1061,13 @@ vec![
deprecation: None,
module: "large_stack_arrays",
},
Lint {
name: "large_types_passed_by_value",
group: "pedantic",
desc: "functions taking large arguments by value",
deprecation: None,
module: "pass_by_ref_or_value",
},
Lint {
name: "len_without_is_empty",
group: "style",
@ -2389,7 +2396,7 @@ vec![
group: "pedantic",
desc: "functions taking small copyable arguments by reference",
deprecation: None,
module: "trivially_copy_pass_by_ref",
module: "pass_by_ref_or_value",
},
Lint {
name: "try_err",

2
tests/ui-toml/toml_unknown_key/conf_unknown_key.stderr
View file

@ -1,4 +1,4 @@
error: error reading Clippy's configuration file `$DIR/clippy.toml`: unknown field `foobar`, expected one of `blacklisted-names`, `cognitive-complexity-threshold`, `cyclomatic-complexity-threshold`, `doc-valid-idents`, `too-many-arguments-threshold`, `type-complexity-threshold`, `single-char-binding-names-threshold`, `too-large-for-stack`, `enum-variant-name-threshold`, `enum-variant-size-threshold`, `verbose-bit-mask-threshold`, `literal-representation-threshold`, `trivial-copy-size-limit`, `too-many-lines-threshold`, `array-size-threshold`, `vec-box-size-threshold`, `max-trait-bounds`, `max-struct-bools`, `max-fn-params-bools`, `warn-on-all-wildcard-imports`, `disallowed-methods`, `third-party` at line 5 column 1
error: error reading Clippy's configuration file `$DIR/clippy.toml`: unknown field `foobar`, expected one of `blacklisted-names`, `cognitive-complexity-threshold`, `cyclomatic-complexity-threshold`, `doc-valid-idents`, `too-many-arguments-threshold`, `type-complexity-threshold`, `single-char-binding-names-threshold`, `too-large-for-stack`, `enum-variant-name-threshold`, `enum-variant-size-threshold`, `verbose-bit-mask-threshold`, `literal-representation-threshold`, `trivial-copy-size-limit`, `pass-by-value-size-limit`, `too-many-lines-threshold`, `array-size-threshold`, `vec-box-size-threshold`, `max-trait-bounds`, `max-struct-bools`, `max-fn-params-bools`, `warn-on-all-wildcard-imports`, `disallowed-methods`, `third-party` at line 5 column 1
error: aborting due to previous error

66
tests/ui/large_types_passed_by_value.rs Normal file
View file

@ -0,0 +1,66 @@
// normalize-stderr-test "\(\d+ byte\)" -> "(N byte)"
// normalize-stderr-test "\(limit: \d+ byte\)" -> "(limit: N byte)"
#![warn(clippy::large_types_passed_by_value)]
pub struct Large([u8; 2048]);
#[derive(Clone, Copy)]
pub struct LargeAndCopy([u8; 2048]);
pub struct Small([u8; 4]);
#[derive(Clone, Copy)]
pub struct SmallAndCopy([u8; 4]);
fn small(a: Small, b: SmallAndCopy) {}
fn not_copy(a: Large) {}
fn by_ref(a: &Large, b: &LargeAndCopy) {}
fn mutable(mut a: LargeAndCopy) {}
fn bad(a: LargeAndCopy) {}
pub fn bad_but_pub(a: LargeAndCopy) {}
impl LargeAndCopy {
fn self_is_ok(self) {}
fn other_is_not_ok(self, other: LargeAndCopy) {}
fn unless_other_can_change(self, mut other: LargeAndCopy) {}
pub fn or_were_in_public(self, other: LargeAndCopy) {}
}
trait LargeTypeDevourer {
fn devoure_array(&self, array: [u8; 6666]);
fn devoure_tuple(&self, tup: (LargeAndCopy, LargeAndCopy));
fn devoure_array_and_tuple_wow(&self, array: [u8; 6666], tup: (LargeAndCopy, LargeAndCopy));
}
pub trait PubLargeTypeDevourer {
fn devoure_array_in_public(&self, array: [u8; 6666]);
}
struct S {}
impl LargeTypeDevourer for S {
fn devoure_array(&self, array: [u8; 6666]) {
todo!();
}
fn devoure_tuple(&self, tup: (LargeAndCopy, LargeAndCopy)) {
todo!();
}
fn devoure_array_and_tuple_wow(&self, array: [u8; 6666], tup: (LargeAndCopy, LargeAndCopy)) {
todo!();
}
}
#[inline(always)]
fn foo_always(x: LargeAndCopy) {
todo!();
}
#[inline(never)]
fn foo_never(x: LargeAndCopy) {
todo!();
}
#[inline]
fn foo(x: LargeAndCopy) {
todo!();
}
fn main() {}

52
tests/ui/large_types_passed_by_value.stderr Normal file
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@ -0,0 +1,52 @@
error: this argument (N byte) is passed by value, but might be more efficient if passed by reference (limit: N byte)
--> $DIR/large_types_passed_by_value.rs:20:11
|
LL | fn bad(a: LargeAndCopy) {}
| ^^^^^^^^^^^^ help: consider passing by reference instead: `&LargeAndCopy`
|
= note: `-D clippy::large-types-passed-by-value` implied by `-D warnings`
error: this argument (N byte) is passed by value, but might be more efficient if passed by reference (limit: N byte)
--> $DIR/large_types_passed_by_value.rs:25:37
|
LL | fn other_is_not_ok(self, other: LargeAndCopy) {}
| ^^^^^^^^^^^^ help: consider passing by reference instead: `&LargeAndCopy`
error: this argument (N byte) is passed by value, but might be more efficient if passed by reference (limit: N byte)
--> $DIR/large_types_passed_by_value.rs:31:36
|
LL | fn devoure_array(&self, array: [u8; 6666]);
| ^^^^^^^^^^ help: consider passing by reference instead: `&[u8; 6666]`
error: this argument (N byte) is passed by value, but might be more efficient if passed by reference (limit: N byte)
--> $DIR/large_types_passed_by_value.rs:32:34
|
LL | fn devoure_tuple(&self, tup: (LargeAndCopy, LargeAndCopy));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider passing by reference instead: `&(LargeAndCopy, LargeAndCopy)`
error: this argument (N byte) is passed by value, but might be more efficient if passed by reference (limit: N byte)
--> $DIR/large_types_passed_by_value.rs:33:50
|
LL | fn devoure_array_and_tuple_wow(&self, array: [u8; 6666], tup: (LargeAndCopy, LargeAndCopy));
| ^^^^^^^^^^ help: consider passing by reference instead: `&[u8; 6666]`
error: this argument (N byte) is passed by value, but might be more efficient if passed by reference (limit: N byte)
--> $DIR/large_types_passed_by_value.rs:33:67
|
LL | fn devoure_array_and_tuple_wow(&self, array: [u8; 6666], tup: (LargeAndCopy, LargeAndCopy));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider passing by reference instead: `&(LargeAndCopy, LargeAndCopy)`
error: this argument (N byte) is passed by value, but might be more efficient if passed by reference (limit: N byte)
--> $DIR/large_types_passed_by_value.rs:58:17
|
LL | fn foo_never(x: LargeAndCopy) {
| ^^^^^^^^^^^^ help: consider passing by reference instead: `&LargeAndCopy`
error: this argument (N byte) is passed by value, but might be more efficient if passed by reference (limit: N byte)
--> $DIR/large_types_passed_by_value.rs:62:11
|
LL | fn foo(x: LargeAndCopy) {
| ^^^^^^^^^^^^ help: consider passing by reference instead: `&LargeAndCopy`
error: aborting due to 8 previous errors