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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{indent_of, reindent_multiline, snippet};
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{is_trait_method, path_to_local_id, peel_blocks, SpanlessEq};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::def::Res;
use rustc_hir::{Closure, Expr, ExprKind, PatKind, PathSegment, QPath, UnOp};
use rustc_lint::LateContext;
use rustc_middle::ty::adjustment::Adjust;
use rustc_span::source_map::Span;
use rustc_span::symbol::{sym, Symbol};
use std::borrow::Cow;
use super::MANUAL_FILTER_MAP;
use super::MANUAL_FIND_MAP;
use super::OPTION_FILTER_MAP;
fn is_method<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, method_name: Symbol) -> bool {
match &expr.kind {
hir::ExprKind::Path(QPath::TypeRelative(_, mname)) => mname.ident.name == method_name,
hir::ExprKind::Path(QPath::Resolved(_, segments)) => {
segments.segments.last().unwrap().ident.name == method_name
},
hir::ExprKind::Closure(&hir::Closure { body, .. }) => {
let body = cx.tcx.hir().body(body);
let closure_expr = peel_blocks(&body.value);
let arg_id = body.params[0].pat.hir_id;
match closure_expr.kind {
hir::ExprKind::MethodCall(hir::PathSegment { ident, .. }, args, _) => {
if_chain! {
if ident.name == method_name;
if let hir::ExprKind::Path(path) = &args[0].kind;
if let Res::Local(ref local) = cx.qpath_res(path, args[0].hir_id);
then {
return arg_id == *local
}
}
false
},
_ => false,
}
},
_ => false,
}
}
fn is_option_filter_map<'tcx>(cx: &LateContext<'tcx>, filter_arg: &hir::Expr<'_>, map_arg: &hir::Expr<'_>) -> bool {
is_method(cx, map_arg, sym::unwrap) && is_method(cx, filter_arg, sym!(is_some))
}
/// is `filter(|x| x.is_some()).map(|x| x.unwrap())`
fn is_filter_some_map_unwrap(
cx: &LateContext<'_>,
expr: &hir::Expr<'_>,
filter_recv: &hir::Expr<'_>,
filter_arg: &hir::Expr<'_>,
map_arg: &hir::Expr<'_>,
) -> bool {
let iterator = is_trait_method(cx, expr, sym::Iterator);
let option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(filter_recv), sym::Option);
(iterator || option) && is_option_filter_map(cx, filter_arg, map_arg)
}
/// lint use of `filter().map()` or `find().map()` for `Iterators`
#[allow(clippy::too_many_arguments)]
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
expr: &hir::Expr<'_>,
filter_recv: &hir::Expr<'_>,
filter_arg: &hir::Expr<'_>,
filter_span: Span,
map_recv: &hir::Expr<'_>,
map_arg: &hir::Expr<'_>,
map_span: Span,
is_find: bool,
) {
if is_filter_some_map_unwrap(cx, expr, filter_recv, filter_arg, map_arg) {
span_lint_and_sugg(
cx,
OPTION_FILTER_MAP,
filter_span.with_hi(expr.span.hi()),
"`filter` for `Some` followed by `unwrap`",
"consider using `flatten` instead",
reindent_multiline(Cow::Borrowed("flatten()"), true, indent_of(cx, map_span)).into_owned(),
Applicability::MachineApplicable,
);
return;
}
if_chain! {
if is_trait_method(cx, map_recv, sym::Iterator);
// filter(|x| ...is_some())...
if let ExprKind::Closure(&Closure { body: filter_body_id, .. }) = filter_arg.kind;
let filter_body = cx.tcx.hir().body(filter_body_id);
if let [filter_param] = filter_body.params;
// optional ref pattern: `filter(|&x| ..)`
let (filter_pat, is_filter_param_ref) = if let PatKind::Ref(ref_pat, _) = filter_param.pat.kind {
(ref_pat, true)
} else {
(filter_param.pat, false)
};
// closure ends with is_some() or is_ok()
if let PatKind::Binding(_, filter_param_id, _, None) = filter_pat.kind;
if let ExprKind::MethodCall(path, [filter_arg], _) = filter_body.value.kind;
if let Some(opt_ty) = cx.typeck_results().expr_ty(filter_arg).peel_refs().ty_adt_def();
if let Some(is_result) = if cx.tcx.is_diagnostic_item(sym::Option, opt_ty.did()) {
Some(false)
} else if cx.tcx.is_diagnostic_item(sym::Result, opt_ty.did()) {
Some(true)
} else {
None
};
if path.ident.name.as_str() == if is_result { "is_ok" } else { "is_some" };
// ...map(|x| ...unwrap())
if let ExprKind::Closure(&Closure { body: map_body_id, .. }) = map_arg.kind;
let map_body = cx.tcx.hir().body(map_body_id);
if let [map_param] = map_body.params;
if let PatKind::Binding(_, map_param_id, map_param_ident, None) = map_param.pat.kind;
// closure ends with expect() or unwrap()
if let ExprKind::MethodCall(seg, [map_arg, ..], _) = map_body.value.kind;
if matches!(seg.ident.name, sym::expect | sym::unwrap | sym::unwrap_or);
// .filter(..).map(|y| f(y).copied().unwrap())
// ~~~~
let map_arg_peeled = match map_arg.kind {
ExprKind::MethodCall(method, [original_arg], _) if acceptable_methods(method) => {
original_arg
},
_ => map_arg,
};
// .filter(|x| x.is_some()).map(|y| y[.acceptable_method()].unwrap())
let simple_equal = path_to_local_id(filter_arg, filter_param_id)
&& path_to_local_id(map_arg_peeled, map_param_id);
let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| {
// in `filter(|x| ..)`, replace `*x` with `x`
let a_path = if_chain! {
if !is_filter_param_ref;
if let ExprKind::Unary(UnOp::Deref, expr_path) = a.kind;
then { expr_path } else { a }
};
// let the filter closure arg and the map closure arg be equal
path_to_local_id(a_path, filter_param_id)
&& path_to_local_id(b, map_param_id)
&& cx.typeck_results().expr_ty_adjusted(a) == cx.typeck_results().expr_ty_adjusted(b)
};
if simple_equal || SpanlessEq::new(cx).expr_fallback(eq_fallback).eq_expr(filter_arg, map_arg_peeled);
then {
let span = filter_span.with_hi(expr.span.hi());
let (filter_name, lint) = if is_find {
("find", MANUAL_FIND_MAP)
} else {
("filter", MANUAL_FILTER_MAP)
};
let msg = format!("`{filter_name}(..).map(..)` can be simplified as `{filter_name}_map(..)`");
let (to_opt, deref) = if is_result {
(".ok()", String::new())
} else {
let derefs = cx.typeck_results()
.expr_adjustments(map_arg)
.iter()
.filter(|adj| matches!(adj.kind, Adjust::Deref(_)))
.count();
("", "*".repeat(derefs))
};
let sugg = format!(
"{filter_name}_map(|{map_param_ident}| {deref}{}{to_opt})",
snippet(cx, map_arg.span, ".."),
);
span_lint_and_sugg(cx, lint, span, &msg, "try", sugg, Applicability::MachineApplicable);
}
}
}
fn acceptable_methods(method: &PathSegment<'_>) -> bool {
let methods: [Symbol; 8] = [
sym::clone,
sym::as_ref,
sym!(copied),
sym!(cloned),
sym!(as_deref),
sym!(as_mut),
sym!(as_deref_mut),
sym!(to_owned),
];
methods.contains(&method.ident.name)
}
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