fix type suggestion for manual_is_ascii_check (#13913)

clippy_lints/src/manual_is_ascii_check.rs

@@ -123,18 +123,15 @@ impl<'tcx> LateLintPass<'tcx> for ManualIsAsciiCheck {
     extract_msrv_attr!(LateContext);
 }
 
-fn get_ty_sugg(cx: &LateContext<'_>, arg: &Expr<'_>, bound_expr: &Expr<'_>) -> Option<(Span, &'static str)> {
-    if let ExprKind::Lit(lit) = bound_expr.kind
+fn get_ty_sugg(cx: &LateContext<'_>, arg: &Expr<'_>, bound_expr: &Expr<'_>) -> Option<(Span, String)> {
+    if let ExprKind::Lit(_) = bound_expr.kind
         && let local_hid = path_to_local(arg)?
         && let Node::Param(Param { ty_span, span, .. }) = cx.tcx.parent_hir_node(local_hid)
         // `ty_span` and `span` are the same for inferred type, thus a type suggestion must be given
         && ty_span == span
     {
-        let ty_str = match lit.node {
-            Char(_) => "char",
-            Byte(_) => "u8",
-            _ => return None,
-        };
+        let arg_type = cx.typeck_results().expr_ty(arg);
+        let ty_str = arg_type.to_string();
         return Some((*ty_span, ty_str));
     }
     None
@@ -145,7 +142,7 @@ fn check_is_ascii(
     span: Span,
     recv: &Expr<'_>,
     range: &CharRange,
-    ty_sugg: Option<(Span, &'_ str)>,
+    ty_sugg: Option<(Span, String)>,
 ) {
     let sugg = match range {
         CharRange::UpperChar => "is_ascii_uppercase",

tests/ui/manual_is_ascii_check.fixed

@@ -82,3 +82,8 @@ fn generics() {
     take_while(|c: u8| c.is_ascii_uppercase());
     take_while(|c: char| c.is_ascii_uppercase());
 }
+
+fn adds_type_reference() {
+    let digits: Vec<&char> = ['1', 'A'].iter().take_while(|c: &&char| c.is_ascii_digit()).collect();
+    let digits: Vec<&mut char> = ['1', 'A'].iter_mut().take_while(|c: &&mut char| c.is_ascii_digit()).collect();
+}

tests/ui/manual_is_ascii_check.rs

@@ -82,3 +82,8 @@ fn generics() {
     take_while(|c| (b'A'..=b'Z').contains(&c));
     take_while(|c: char| ('A'..='Z').contains(&c));
 }
+
+fn adds_type_reference() {
+    let digits: Vec<&char> = ['1', 'A'].iter().take_while(|c| ('0'..='9').contains(c)).collect();
+    let digits: Vec<&mut char> = ['1', 'A'].iter_mut().take_while(|c| ('0'..='9').contains(c)).collect();
+}

tests/ui/manual_is_ascii_check.stderr

@@ -173,5 +173,27 @@ error: manual check for common ascii range
 LL |     take_while(|c: char| ('A'..='Z').contains(&c));
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `c.is_ascii_uppercase()`
 
-error: aborting due to 27 previous errors
+error: manual check for common ascii range
+  --> tests/ui/manual_is_ascii_check.rs:87:63
+   |
+LL |     let digits: Vec<&char> = ['1', 'A'].iter().take_while(|c| ('0'..='9').contains(c)).collect();
+   |                                                               ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: try
+   |
+LL |     let digits: Vec<&char> = ['1', 'A'].iter().take_while(|c: &&char| c.is_ascii_digit()).collect();
+   |                                                            ~~~~~~~~~  ~~~~~~~~~~~~~~~~~~
+
+error: manual check for common ascii range
+  --> tests/ui/manual_is_ascii_check.rs:88:71
+   |
+LL |     let digits: Vec<&mut char> = ['1', 'A'].iter_mut().take_while(|c| ('0'..='9').contains(c)).collect();
+   |                                                                       ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: try
+   |
+LL |     let digits: Vec<&mut char> = ['1', 'A'].iter_mut().take_while(|c: &&mut char| c.is_ascii_digit()).collect();
+   |                                                                    ~~~~~~~~~~~~~  ~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 29 previous errors