1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
|
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_trait_method;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::ty::is_type_diagnostic_item;
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty;
use rustc_span::{symbol::sym, Span};
use super::MAP_FLATTEN;
/// lint use of `map().flatten()` for `Iterators` and 'Options'
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, map_arg: &Expr<'_>, map_span: Span) {
if let Some((caller_ty_name, method_to_use)) = try_get_caller_ty_name_and_method_name(cx, expr, recv, map_arg) {
let mut applicability = Applicability::MachineApplicable;
let closure_snippet = snippet_with_applicability(cx, map_arg.span, "..", &mut applicability);
span_lint_and_sugg(
cx,
MAP_FLATTEN,
expr.span.with_lo(map_span.lo()),
&format!("called `map(..).flatten()` on `{caller_ty_name}`"),
&format!("try replacing `map` with `{method_to_use}` and remove the `.flatten()`"),
format!("{method_to_use}({closure_snippet})"),
applicability,
);
}
}
fn try_get_caller_ty_name_and_method_name(
cx: &LateContext<'_>,
expr: &Expr<'_>,
caller_expr: &Expr<'_>,
map_arg: &Expr<'_>,
) -> Option<(&'static str, &'static str)> {
if is_trait_method(cx, expr, sym::Iterator) {
if is_map_to_option(cx, map_arg) {
// `(...).map(...)` has type `impl Iterator<Item=Option<...>>
Some(("Iterator", "filter_map"))
} else {
// `(...).map(...)` has type `impl Iterator<Item=impl Iterator<...>>
Some(("Iterator", "flat_map"))
}
} else {
if let ty::Adt(adt, _) = cx.typeck_results().expr_ty(caller_expr).kind() {
if cx.tcx.is_diagnostic_item(sym::Option, adt.did()) {
return Some(("Option", "and_then"));
} else if cx.tcx.is_diagnostic_item(sym::Result, adt.did()) {
return Some(("Result", "and_then"));
}
}
None
}
}
fn is_map_to_option(cx: &LateContext<'_>, map_arg: &Expr<'_>) -> bool {
let map_closure_ty = cx.typeck_results().expr_ty(map_arg);
match map_closure_ty.kind() {
ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
let map_closure_sig = match map_closure_ty.kind() {
ty::Closure(_, substs) => substs.as_closure().sig(),
_ => map_closure_ty.fn_sig(cx.tcx),
};
let map_closure_return_ty = cx.tcx.erase_late_bound_regions(map_closure_sig.output());
is_type_diagnostic_item(cx, map_closure_return_ty, sym::Option)
},
_ => false,
}
}
|
