move get_hint_if_single_char_arg to methods/utils.rs

1 files changed, 33 insertions, 1 deletions

diff --git a/clippy_lints/src/methods/utils.rs b/clippy_lints/src/methods/utils.rs
index 4d801148cbc..8de23e1bc6e 100644
--- a/clippy_lints/src/methods/utils.rs
+++ b/clippy_lints/src/methods/utils.rs
@@ -1,11 +1,15 @@
+use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::is_type_diagnostic_item;
+use if_chain::if_chain;
+use rustc_ast::ast;
+use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
 use rustc_middle::ty;
 use rustc_middle::ty::Ty;
 use rustc_span::symbol::sym;
 
-pub fn derefs_to_slice<'tcx>(
+pub(super) fn derefs_to_slice<'tcx>(
     cx: &LateContext<'tcx>,
     expr: &'tcx hir::Expr<'tcx>,
     ty: Ty<'tcx>,
@@ -44,3 +48,31 @@ pub fn derefs_to_slice<'tcx>(
         }
     }
 }
+
+pub(super) fn get_hint_if_single_char_arg(
+    cx: &LateContext<'_>,
+    arg: &hir::Expr<'_>,
+    applicability: &mut Applicability,
+) -> Option<String> {
+    if_chain! {
+        if let hir::ExprKind::Lit(lit) = &arg.kind;
+        if let ast::LitKind::Str(r, style) = lit.node;
+        let string = r.as_str();
+        if string.chars().count() == 1;
+        then {
+            let snip = snippet_with_applicability(cx, arg.span, &string, applicability);
+            let ch = if let ast::StrStyle::Raw(nhash) = style {
+                let nhash = nhash as usize;
+                // for raw string: r##"a"##
+                &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
+            } else {
+                // for regular string: "a"
+                &snip[1..(snip.len() - 1)]
+            };
+            let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
+            Some(hint)
+        } else {
+            None
+        }
+    }
+}