Update upstream source from tag 'upstream/1.52.1+dfsg1'

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

diff --git a/src/tools/clippy/clippy_lints/src/methods/bytes_nth.rs b/src/tools/clippy/clippy_lints/src/methods/bytes_nth.rs
new file mode 100644 (file)
index 0000000..71a7e19
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/methods/bytes_nth.rs
@@ -0,0 +1,39 @@
+use crate::utils::{is_type_diagnostic_item, snippet_with_applicability, span_lint_and_sugg};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_span::sym;
+
+use super::BYTES_NTH;
+
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, iter_args: &'tcx [Expr<'tcx>]) {
+    if_chain! {
+        if let ExprKind::MethodCall(_, _, ref args, _) = expr.kind;
+        let ty = cx.typeck_results().expr_ty(&iter_args[0]).peel_refs();
+        let caller_type = if is_type_diagnostic_item(cx, ty, sym::string_type) {
+            Some("String")
+        } else if ty.is_str() {
+            Some("str")
+        } else {
+            None
+        };
+        if let Some(caller_type) = caller_type;
+        then {
+            let mut applicability = Applicability::MachineApplicable;
+            span_lint_and_sugg(
+                cx,
+                BYTES_NTH,
+                expr.span,
+                &format!("called `.byte().nth()` on a `{}`", caller_type),
+                "try",
+                format!(
+                    "{}.as_bytes().get({})",
+                    snippet_with_applicability(cx, iter_args[0].span, "..", &mut applicability),
+                    snippet_with_applicability(cx, args[1].span, "..", &mut applicability)
+                ),
+                applicability,
+            );
+        }
+    }
+}