Merge tag 'debian/1.52.1+dfsg1-1_exp2' into proxmox/buster

[rustc.git] / src / tools / clippy / clippy_lints / src / loops / single_element_loop.rs

diff --git a/src/tools/clippy/clippy_lints/src/loops/single_element_loop.rs b/src/tools/clippy/clippy_lints/src/loops/single_element_loop.rs
new file mode 100644 (file)
index 0000000..38400c9
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/loops/single_element_loop.rs
@@ -0,0 +1,42 @@
+use super::{get_span_of_entire_for_loop, SINGLE_ELEMENT_LOOP};
+use crate::utils::{indent_of, single_segment_path, snippet, span_lint_and_sugg};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{BorrowKind, Expr, ExprKind, Pat, PatKind};
+use rustc_lint::LateContext;
+
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    pat: &'tcx Pat<'_>,
+    arg: &'tcx Expr<'_>,
+    body: &'tcx Expr<'_>,
+    expr: &'tcx Expr<'_>,
+) {
+    if_chain! {
+        if let ExprKind::AddrOf(BorrowKind::Ref, _, ref arg_expr) = arg.kind;
+        if let PatKind::Binding(.., target, _) = pat.kind;
+        if let ExprKind::Array([arg_expression]) = arg_expr.kind;
+        if let ExprKind::Path(ref list_item) = arg_expression.kind;
+        if let Some(list_item_name) = single_segment_path(list_item).map(|ps| ps.ident.name);
+        if let ExprKind::Block(ref block, _) = body.kind;
+        if !block.stmts.is_empty();
+
+        then {
+            let for_span = get_span_of_entire_for_loop(expr);
+            let mut block_str = snippet(cx, block.span, "..").into_owned();
+            block_str.remove(0);
+            block_str.pop();
+
+
+            span_lint_and_sugg(
+                cx,
+                SINGLE_ELEMENT_LOOP,
+                for_span,
+                "for loop over a single element",
+                "try",
+                format!("{{\n{}let {} = &{};{}}}", " ".repeat(indent_of(cx, block.stmts[0].span).unwrap_or(0)), target.name, list_item_name, block_str),
+                Applicability::MachineApplicable
+            )
+        }
+    }
+}