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

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

diff --git a/src/tools/clippy/clippy_lints/src/methods/string_extend_chars.rs b/src/tools/clippy/clippy_lints/src/methods/string_extend_chars.rs
new file mode 100644 (file)
index 0000000..0a08ea2
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/methods/string_extend_chars.rs
@@ -0,0 +1,42 @@
+use crate::utils::{is_type_diagnostic_item, method_chain_args, snippet_with_applicability, span_lint_and_sugg};
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_middle::ty;
+use rustc_span::symbol::sym;
+
+use super::STRING_EXTEND_CHARS;
+
+pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
+    let obj_ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
+    if is_type_diagnostic_item(cx, obj_ty, sym::string_type) {
+        let arg = &args[1];
+        if let Some(arglists) = method_chain_args(arg, &["chars"]) {
+            let target = &arglists[0][0];
+            let self_ty = cx.typeck_results().expr_ty(target).peel_refs();
+            let ref_str = if *self_ty.kind() == ty::Str {
+                ""
+            } else if is_type_diagnostic_item(cx, self_ty, sym::string_type) {
+                "&"
+            } else {
+                return;
+            };
+
+            let mut applicability = Applicability::MachineApplicable;
+            span_lint_and_sugg(
+                cx,
+                STRING_EXTEND_CHARS,
+                expr.span,
+                "calling `.extend(_.chars())`",
+                "try this",
+                format!(
+                    "{}.push_str({}{})",
+                    snippet_with_applicability(cx, args[0].span, "..", &mut applicability),
+                    ref_str,
+                    snippet_with_applicability(cx, target.span, "..", &mut applicability)
+                ),
+                applicability,
+            );
+        }
+    }
+}