232 lines
8.2 KiB
Rust
232 lines
8.2 KiB
Rust
use if_chain::if_chain;
|
|
use rustc_errors::Applicability;
|
|
use rustc_hir::{def_id, Expr, ExprKind, Param, PatKind, QPath};
|
|
use rustc_lint::{LateContext, LateLintPass, LintContext};
|
|
use rustc_middle::lint::in_external_macro;
|
|
use rustc_middle::ty::{self, Ty};
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
|
|
|
use crate::utils::{
|
|
implements_trait, is_adjusted, iter_input_pats, snippet_opt, span_lint_and_sugg, span_lint_and_then,
|
|
type_is_unsafe_function,
|
|
};
|
|
|
|
declare_clippy_lint! {
|
|
/// **What it does:** Checks for closures which just call another function where
|
|
/// the function can be called directly. `unsafe` functions or calls where types
|
|
/// get adjusted are ignored.
|
|
///
|
|
/// **Why is this bad?** Needlessly creating a closure adds code for no benefit
|
|
/// and gives the optimizer more work.
|
|
///
|
|
/// **Known problems:** If creating the closure inside the closure has a side-
|
|
/// effect then moving the closure creation out will change when that side-
|
|
/// effect runs.
|
|
/// See rust-lang/rust-clippy#1439 for more details.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust,ignore
|
|
/// // Bad
|
|
/// xs.map(|x| foo(x))
|
|
///
|
|
/// // Good
|
|
/// xs.map(foo)
|
|
/// ```
|
|
/// where `foo(_)` is a plain function that takes the exact argument type of
|
|
/// `x`.
|
|
pub REDUNDANT_CLOSURE,
|
|
style,
|
|
"redundant closures, i.e., `|a| foo(a)` (which can be written as just `foo`)"
|
|
}
|
|
|
|
declare_clippy_lint! {
|
|
/// **What it does:** Checks for closures which only invoke a method on the closure
|
|
/// argument and can be replaced by referencing the method directly.
|
|
///
|
|
/// **Why is this bad?** It's unnecessary to create the closure.
|
|
///
|
|
/// **Known problems:** rust-lang/rust-clippy#3071, rust-lang/rust-clippy#4002,
|
|
/// rust-lang/rust-clippy#3942
|
|
///
|
|
///
|
|
/// **Example:**
|
|
/// ```rust,ignore
|
|
/// Some('a').map(|s| s.to_uppercase());
|
|
/// ```
|
|
/// may be rewritten as
|
|
/// ```rust,ignore
|
|
/// Some('a').map(char::to_uppercase);
|
|
/// ```
|
|
pub REDUNDANT_CLOSURE_FOR_METHOD_CALLS,
|
|
pedantic,
|
|
"redundant closures for method calls"
|
|
}
|
|
|
|
declare_lint_pass!(EtaReduction => [REDUNDANT_CLOSURE, REDUNDANT_CLOSURE_FOR_METHOD_CALLS]);
|
|
|
|
impl<'tcx> LateLintPass<'tcx> for EtaReduction {
|
|
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
|
|
if in_external_macro(cx.sess(), expr.span) {
|
|
return;
|
|
}
|
|
|
|
match expr.kind {
|
|
ExprKind::Call(_, args) | ExprKind::MethodCall(_, _, args, _) => {
|
|
for arg in args {
|
|
check_closure(cx, arg)
|
|
}
|
|
},
|
|
_ => (),
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_closure(cx: &LateContext<'_>, expr: &Expr<'_>) {
|
|
if let ExprKind::Closure(_, ref decl, eid, _, _) = expr.kind {
|
|
let body = cx.tcx.hir().body(eid);
|
|
let ex = &body.value;
|
|
|
|
if_chain!(
|
|
if let ExprKind::Call(ref caller, ref args) = ex.kind;
|
|
|
|
if let ExprKind::Path(_) = caller.kind;
|
|
|
|
// Not the same number of arguments, there is no way the closure is the same as the function return;
|
|
if args.len() == decl.inputs.len();
|
|
|
|
// Are the expression or the arguments type-adjusted? Then we need the closure
|
|
if !(is_adjusted(cx, ex) || args.iter().any(|arg| is_adjusted(cx, arg)));
|
|
|
|
let fn_ty = cx.tables().expr_ty(caller);
|
|
|
|
if matches!(fn_ty.kind, ty::FnDef(_, _) | ty::FnPtr(_) | ty::Closure(_, _));
|
|
|
|
if !type_is_unsafe_function(cx, fn_ty);
|
|
|
|
if compare_inputs(&mut iter_input_pats(decl, body), &mut args.iter());
|
|
|
|
then {
|
|
span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure found", |diag| {
|
|
if let Some(snippet) = snippet_opt(cx, caller.span) {
|
|
diag.span_suggestion(
|
|
expr.span,
|
|
"remove closure as shown",
|
|
snippet,
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|
|
});
|
|
}
|
|
);
|
|
|
|
if_chain!(
|
|
if let ExprKind::MethodCall(ref path, _, ref args, _) = ex.kind;
|
|
|
|
// Not the same number of arguments, there is no way the closure is the same as the function return;
|
|
if args.len() == decl.inputs.len();
|
|
|
|
// Are the expression or the arguments type-adjusted? Then we need the closure
|
|
if !(is_adjusted(cx, ex) || args.iter().skip(1).any(|arg| is_adjusted(cx, arg)));
|
|
|
|
let method_def_id = cx.tables().type_dependent_def_id(ex.hir_id).unwrap();
|
|
if !type_is_unsafe_function(cx, cx.tcx.type_of(method_def_id));
|
|
|
|
if compare_inputs(&mut iter_input_pats(decl, body), &mut args.iter());
|
|
|
|
if let Some(name) = get_ufcs_type_name(cx, method_def_id, &args[0]);
|
|
|
|
then {
|
|
span_lint_and_sugg(
|
|
cx,
|
|
REDUNDANT_CLOSURE_FOR_METHOD_CALLS,
|
|
expr.span,
|
|
"redundant closure found",
|
|
"remove closure as shown",
|
|
format!("{}::{}", name, path.ident.name),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|
|
);
|
|
}
|
|
}
|
|
|
|
/// Tries to determine the type for universal function call to be used instead of the closure
|
|
fn get_ufcs_type_name(cx: &LateContext<'_>, method_def_id: def_id::DefId, self_arg: &Expr<'_>) -> Option<String> {
|
|
let expected_type_of_self = &cx.tcx.fn_sig(method_def_id).inputs_and_output().skip_binder()[0];
|
|
let actual_type_of_self = &cx.tables().node_type(self_arg.hir_id);
|
|
|
|
if let Some(trait_id) = cx.tcx.trait_of_item(method_def_id) {
|
|
if match_borrow_depth(expected_type_of_self, &actual_type_of_self)
|
|
&& implements_trait(cx, actual_type_of_self, trait_id, &[])
|
|
{
|
|
return Some(cx.tcx.def_path_str(trait_id));
|
|
}
|
|
}
|
|
|
|
cx.tcx.impl_of_method(method_def_id).and_then(|_| {
|
|
//a type may implicitly implement other type's methods (e.g. Deref)
|
|
if match_types(expected_type_of_self, &actual_type_of_self) {
|
|
return Some(get_type_name(cx, &actual_type_of_self));
|
|
}
|
|
None
|
|
})
|
|
}
|
|
|
|
fn match_borrow_depth(lhs: Ty<'_>, rhs: Ty<'_>) -> bool {
|
|
match (&lhs.kind, &rhs.kind) {
|
|
(ty::Ref(_, t1, mut1), ty::Ref(_, t2, mut2)) => mut1 == mut2 && match_borrow_depth(&t1, &t2),
|
|
(l, r) => match (l, r) {
|
|
(ty::Ref(_, _, _), _) | (_, ty::Ref(_, _, _)) => false,
|
|
(_, _) => true,
|
|
},
|
|
}
|
|
}
|
|
|
|
fn match_types(lhs: Ty<'_>, rhs: Ty<'_>) -> bool {
|
|
match (&lhs.kind, &rhs.kind) {
|
|
(ty::Bool, ty::Bool)
|
|
| (ty::Char, ty::Char)
|
|
| (ty::Int(_), ty::Int(_))
|
|
| (ty::Uint(_), ty::Uint(_))
|
|
| (ty::Str, ty::Str) => true,
|
|
(ty::Ref(_, t1, mut1), ty::Ref(_, t2, mut2)) => mut1 == mut2 && match_types(t1, t2),
|
|
(ty::Array(t1, _), ty::Array(t2, _)) | (ty::Slice(t1), ty::Slice(t2)) => match_types(t1, t2),
|
|
(ty::Adt(def1, _), ty::Adt(def2, _)) => def1 == def2,
|
|
(_, _) => false,
|
|
}
|
|
}
|
|
|
|
fn get_type_name(cx: &LateContext<'_>, ty: Ty<'_>) -> String {
|
|
match ty.kind {
|
|
ty::Adt(t, _) => cx.tcx.def_path_str(t.did),
|
|
ty::Ref(_, r, _) => get_type_name(cx, &r),
|
|
_ => ty.to_string(),
|
|
}
|
|
}
|
|
|
|
fn compare_inputs(
|
|
closure_inputs: &mut dyn Iterator<Item = &Param<'_>>,
|
|
call_args: &mut dyn Iterator<Item = &Expr<'_>>,
|
|
) -> bool {
|
|
for (closure_input, function_arg) in closure_inputs.zip(call_args) {
|
|
if let PatKind::Binding(_, _, ident, _) = closure_input.pat.kind {
|
|
// XXXManishearth Should I be checking the binding mode here?
|
|
if let ExprKind::Path(QPath::Resolved(None, ref p)) = function_arg.kind {
|
|
if p.segments.len() != 1 {
|
|
// If it's a proper path, it can't be a local variable
|
|
return false;
|
|
}
|
|
if p.segments[0].ident.name != ident.name {
|
|
// The two idents should be the same
|
|
return false;
|
|
}
|
|
} else {
|
|
return false;
|
|
}
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
true
|
|
}
|