New upstream version 1.52.1+dfsg1

[rustc.git] / src / tools / clippy / clippy_lints / src / methods / filter_next.rs

diff --git a/src/tools/clippy/clippy_lints/src/methods/filter_next.rs b/src/tools/clippy/clippy_lints/src/methods/filter_next.rs
new file mode 100644 (file)
index 0000000..81619e7
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/methods/filter_next.rs
@@ -0,0 +1,31 @@
+use crate::utils::{match_trait_method, paths, snippet, span_lint, span_lint_and_sugg};
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+
+use super::FILTER_NEXT;
+
+/// lint use of `filter().next()` for `Iterators`
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, filter_args: &'tcx [hir::Expr<'_>]) {
+    // lint if caller of `.filter().next()` is an Iterator
+    if match_trait_method(cx, expr, &paths::ITERATOR) {
+        let msg = "called `filter(..).next()` on an `Iterator`. This is more succinctly expressed by calling \
+                   `.find(..)` instead";
+        let filter_snippet = snippet(cx, filter_args[1].span, "..");
+        if filter_snippet.lines().count() <= 1 {
+            let iter_snippet = snippet(cx, filter_args[0].span, "..");
+            // add note if not multi-line
+            span_lint_and_sugg(
+                cx,
+                FILTER_NEXT,
+                expr.span,
+                msg,
+                "try this",
+                format!("{}.find({})", iter_snippet, filter_snippet),
+                Applicability::MachineApplicable,
+            );
+        } else {
+            span_lint(cx, FILTER_NEXT, expr.span, msg);
+        }
+    }
+}