2022-06-19 14:21:14 -05:00
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use clippy_utils::diagnostics::span_lint_and_sugg;
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2021-03-25 13:29:11 -05:00
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use clippy_utils::is_trait_method;
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use clippy_utils::source::snippet_with_applicability;
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use clippy_utils::ty::is_type_diagnostic_item;
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2021-03-12 08:30:50 -06:00
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use rustc_errors::Applicability;
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use rustc_hir::Expr;
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use rustc_lint::LateContext;
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use rustc_middle::ty;
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use rustc_span::{symbol::sym, Span};
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use super::MAP_FLATTEN;
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/// lint use of `map().flatten()` for `Iterators` and 'Options'
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pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, map_arg: &Expr<'_>, map_span: Span) {
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if let Some((caller_ty_name, method_to_use)) = try_get_caller_ty_name_and_method_name(cx, expr, recv, map_arg) {
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let mut applicability = Applicability::MachineApplicable;
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2022-03-24 08:50:04 -05:00
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let closure_snippet = snippet_with_applicability(cx, map_arg.span, "..", &mut applicability);
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span_lint_and_sugg(
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cx,
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MAP_FLATTEN,
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expr.span.with_lo(map_span.lo()),
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&format!("called `map(..).flatten()` on `{}`", caller_ty_name),
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&format!("try replacing `map` with `{}` and remove the `.flatten()`", method_to_use),
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format!("{}({})", method_to_use, closure_snippet),
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applicability,
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);
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}
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}
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fn try_get_caller_ty_name_and_method_name(
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cx: &LateContext<'_>,
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expr: &Expr<'_>,
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caller_expr: &Expr<'_>,
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map_arg: &Expr<'_>,
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) -> Option<(&'static str, &'static str)> {
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if is_trait_method(cx, expr, sym::Iterator) {
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if is_map_to_option(cx, map_arg) {
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// `(...).map(...)` has type `impl Iterator<Item=Option<...>>
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Some(("Iterator", "filter_map"))
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} else {
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// `(...).map(...)` has type `impl Iterator<Item=impl Iterator<...>>
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Some(("Iterator", "flat_map"))
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}
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} else {
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if let ty::Adt(adt, _) = cx.typeck_results().expr_ty(caller_expr).kind() {
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if cx.tcx.is_diagnostic_item(sym::Option, adt.did()) {
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return Some(("Option", "and_then"));
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} else if cx.tcx.is_diagnostic_item(sym::Result, adt.did()) {
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return Some(("Result", "and_then"));
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2021-08-12 04:16:25 -05:00
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}
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}
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None
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}
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}
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fn is_map_to_option(cx: &LateContext<'_>, map_arg: &Expr<'_>) -> bool {
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let map_closure_ty = cx.typeck_results().expr_ty(map_arg);
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match map_closure_ty.kind() {
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ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
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let map_closure_sig = match map_closure_ty.kind() {
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ty::Closure(_, substs) => substs.as_closure().sig(),
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_ => map_closure_ty.fn_sig(cx.tcx),
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};
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let map_closure_return_ty = cx.tcx.erase_late_bound_regions(map_closure_sig.output());
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is_type_diagnostic_item(cx, map_closure_return_ty, sym::Option)
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},
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_ => false,
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}
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}
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