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use rustc::lint::*;
use rustc::ty;
use rustc::hir::*;
use utils::{snippet_opt, span_lint_and_then, is_adjusted, iter_input_pats};
#[allow(missing_copy_implementations)]
pub struct EtaPass;
declare_lint! {
pub REDUNDANT_CLOSURE,
Warn,
"redundant closures, i.e. `|a| foo(a)` (which can be written as just `foo`)"
}
impl LintPass for EtaPass {
fn get_lints(&self) -> LintArray {
lint_array!(REDUNDANT_CLOSURE)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EtaPass {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
match expr.node {
ExprCall(_, ref args) |
ExprMethodCall(_, _, ref args) => {
for arg in args {
check_closure(cx, arg)
}
},
_ => (),
}
}
}
fn check_closure(cx: &LateContext, expr: &Expr) {
if let ExprClosure(_, ref decl, eid, _) = expr.node {
let body = cx.tcx.map.body(eid);
let ex = &body.value;
if let ExprCall(ref caller, ref args) = ex.node {
if args.len() != decl.inputs.len() {
return;
}
if is_adjusted(cx, ex) || args.iter().any(|arg| is_adjusted(cx, arg)) {
return;
}
let fn_ty = cx.tcx.tables().expr_ty(caller);
match fn_ty.sty {
ty::TyFnDef(_, _, fn_ty) |
ty::TyFnPtr(fn_ty) => {
if fn_ty.unsafety == Unsafety::Unsafe || fn_ty.sig.skip_binder().output().sty == ty::TyNever {
return;
}
},
_ => (),
}
for (a1, a2) in iter_input_pats(decl, body).zip(args) {
if let PatKind::Binding(_, _, ident, _) = a1.pat.node {
if let ExprPath(QPath::Resolved(None, ref p)) = a2.node {
if p.segments.len() != 1 {
return;
}
if p.segments[0].name != ident.node {
return;
}
} else {
return;
}
} else {
return;
}
}
span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure found", |db| {
if let Some(snippet) = snippet_opt(cx, caller.span) {
db.span_suggestion(expr.span, "remove closure as shown:", snippet);
}
});
}
}
}