diff options
| -rw-r--r-- | clippy_lints/src/methods/mod.rs | 40 | ||||
| -rw-r--r-- | tests/ui/map_flatten.fixed | 14 | ||||
| -rw-r--r-- | tests/ui/map_flatten.rs | 14 | ||||
| -rw-r--r-- | tests/ui/map_flatten.stderr | 40 |
4 files changed, 87 insertions, 21 deletions
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs index 9edcdd979ff..9217324b18c 100644 --- a/clippy_lints/src/methods/mod.rs +++ b/clippy_lints/src/methods/mod.rs @@ -2569,17 +2569,34 @@ fn lint_ok_expect(cx: &LateContext<'_>, expr: &hir::Expr<'_>, ok_args: &[hir::Ex fn lint_map_flatten<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_args: &'tcx [hir::Expr<'_>]) { // lint if caller of `.map().flatten()` is an Iterator if match_trait_method(cx, expr, &paths::ITERATOR) { - let msg = "called `map(..).flatten()` on an `Iterator`. \ - This is more succinctly expressed by calling `.flat_map(..)`"; - let self_snippet = snippet(cx, map_args[0].span, ".."); + let map_closure_ty = cx.typeck_results().expr_ty(&map_args[1]); + let is_map_to_option = 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_type)) + }, + _ => false, + }; + + let method_to_use = if is_map_to_option { + // `(...).map(...)` has type `impl Iterator<Item=Option<...>> + "filter_map" + } else { + // `(...).map(...)` has type `impl Iterator<Item=impl Iterator<...>> + "flat_map" + }; let func_snippet = snippet(cx, map_args[1].span, ".."); - let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet); + let hint = format!(".{0}({1})", method_to_use, func_snippet); span_lint_and_sugg( cx, MAP_FLATTEN, - expr.span, - msg, - "try using `flat_map` instead", + expr.span.with_lo(map_args[0].span.hi()), + "called `map(..).flatten()` on an `Iterator`", + &format!("try using `{}` instead", method_to_use), hint, Applicability::MachineApplicable, ); @@ -2587,16 +2604,13 @@ fn lint_map_flatten<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map // lint if caller of `.map().flatten()` is an Option if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym!(option_type)) { - let msg = "called `map(..).flatten()` on an `Option`. \ - This is more succinctly expressed by calling `.and_then(..)`"; - let self_snippet = snippet(cx, map_args[0].span, ".."); let func_snippet = snippet(cx, map_args[1].span, ".."); - let hint = format!("{0}.and_then({1})", self_snippet, func_snippet); + let hint = format!(".and_then({})", func_snippet); span_lint_and_sugg( cx, MAP_FLATTEN, - expr.span, - msg, + expr.span.with_lo(map_args[0].span.hi()), + "called `map(..).flatten()` on an `Option`", "try using `and_then` instead", hint, Applicability::MachineApplicable, diff --git a/tests/ui/map_flatten.fixed b/tests/ui/map_flatten.fixed index 4171d80f48a..a5fdf7df613 100644 --- a/tests/ui/map_flatten.fixed +++ b/tests/ui/map_flatten.fixed @@ -5,6 +5,20 @@ #![allow(clippy::map_identity)] fn main() { + // mapping to Option on Iterator + fn option_id(x: i8) -> Option<i8> { + Some(x) + } + let option_id_ref: fn(i8) -> Option<i8> = option_id; + let option_id_closure = |x| Some(x); + let _: Vec<_> = vec![5_i8; 6].into_iter().filter_map(option_id).collect(); + let _: Vec<_> = vec![5_i8; 6].into_iter().filter_map(option_id_ref).collect(); + let _: Vec<_> = vec![5_i8; 6].into_iter().filter_map(option_id_closure).collect(); + let _: Vec<_> = vec![5_i8; 6].into_iter().filter_map(|x| x.checked_add(1)).collect(); + + // mapping to Iterator on Iterator let _: Vec<_> = vec![5_i8; 6].into_iter().flat_map(|x| 0..x).collect(); + + // mapping to Option on Option let _: Option<_> = (Some(Some(1))).and_then(|x| x); } diff --git a/tests/ui/map_flatten.rs b/tests/ui/map_flatten.rs index 16a0fd090ad..abbc4e16e56 100644 --- a/tests/ui/map_flatten.rs +++ b/tests/ui/map_flatten.rs @@ -5,6 +5,20 @@ #![allow(clippy::map_identity)] fn main() { + // mapping to Option on Iterator + fn option_id(x: i8) -> Option<i8> { + Some(x) + } + let option_id_ref: fn(i8) -> Option<i8> = option_id; + let option_id_closure = |x| Some(x); + let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().collect(); + let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_ref).flatten().collect(); + let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_closure).flatten().collect(); + let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| x.checked_add(1)).flatten().collect(); + + // mapping to Iterator on Iterator let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect(); + + // mapping to Option on Option let _: Option<_> = (Some(Some(1))).map(|x| x).flatten(); } diff --git a/tests/ui/map_flatten.stderr b/tests/ui/map_flatten.stderr index 00bc41c15e9..b6479cd69ea 100644 --- a/tests/ui/map_flatten.stderr +++ b/tests/ui/map_flatten.stderr @@ -1,16 +1,40 @@ -error: called `map(..).flatten()` on an `Iterator`. This is more succinctly expressed by calling `.flat_map(..)` - --> $DIR/map_flatten.rs:8:21 +error: called `map(..).flatten()` on an `Iterator` + --> $DIR/map_flatten.rs:14:46 | -LL | let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect(); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `flat_map` instead: `vec![5_i8; 6].into_iter().flat_map(|x| 0..x)` +LL | let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().collect(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `filter_map` instead: `.filter_map(option_id)` | = note: `-D clippy::map-flatten` implied by `-D warnings` -error: called `map(..).flatten()` on an `Option`. This is more succinctly expressed by calling `.and_then(..)` - --> $DIR/map_flatten.rs:9:24 +error: called `map(..).flatten()` on an `Iterator` + --> $DIR/map_flatten.rs:15:46 + | +LL | let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_ref).flatten().collect(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `filter_map` instead: `.filter_map(option_id_ref)` + +error: called `map(..).flatten()` on an `Iterator` + --> $DIR/map_flatten.rs:16:46 + | +LL | let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_closure).flatten().collect(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `filter_map` instead: `.filter_map(option_id_closure)` + +error: called `map(..).flatten()` on an `Iterator` + --> $DIR/map_flatten.rs:17:46 + | +LL | let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| x.checked_add(1)).flatten().collect(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `filter_map` instead: `.filter_map(|x| x.checked_add(1))` + +error: called `map(..).flatten()` on an `Iterator` + --> $DIR/map_flatten.rs:20:46 + | +LL | let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect(); + | ^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `flat_map` instead: `.flat_map(|x| 0..x)` + +error: called `map(..).flatten()` on an `Option` + --> $DIR/map_flatten.rs:23:39 | LL | let _: Option<_> = (Some(Some(1))).map(|x| x).flatten(); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `and_then` instead: `(Some(Some(1))).and_then(|x| x)` + | ^^^^^^^^^^^^^^^^^^^^^ help: try using `and_then` instead: `.and_then(|x| x)` -error: aborting due to 2 previous errors +error: aborting due to 6 previous errors |