Use method name from conf::DisallowedMethod

Since def_path_str returns e.g. "core::f32::<impl f32>::clamp" for
"f32::clamp"

clippy_lints/src/disallowed_methods.rs

@@ -59,7 +59,7 @@ declare_clippy_lint! {
 #[derive(Clone, Debug)]
 pub struct DisallowedMethods {
     conf_disallowed: Vec<conf::DisallowedMethod>,
-    disallowed: DefIdMap<Option<String>>,
+    disallowed: DefIdMap<usize>,
 }
 
 impl DisallowedMethods {
@@ -75,17 +75,10 @@ impl_lint_pass!(DisallowedMethods => [DISALLOWED_METHODS]);
 
 impl<'tcx> LateLintPass<'tcx> for DisallowedMethods {
     fn check_crate(&mut self, cx: &LateContext<'_>) {
-        for conf in &self.conf_disallowed {
-            let (path, reason) = match conf {
-                conf::DisallowedMethod::Simple(path) => (path, None),
-                conf::DisallowedMethod::WithReason { path, reason } => (
-                    path,
-                    reason.as_ref().map(|reason| format!("{} (from clippy.toml)", reason)),
-                ),
-            };
-            let segs: Vec<_> = path.split("::").collect();
+        for (index, conf) in self.conf_disallowed.iter().enumerate() {
+            let segs: Vec<_> = conf.path().split("::").collect();
             if let Res::Def(_, id) = clippy_utils::path_to_res(cx, &segs) {
-                self.disallowed.insert(id, reason);
+                self.disallowed.insert(id, index);
             }
         }
     }
@@ -95,15 +88,17 @@ impl<'tcx> LateLintPass<'tcx> for DisallowedMethods {
             Some(def_id) => def_id,
             None => return,
         };
-        let reason = match self.disallowed.get(&def_id) {
-            Some(reason) => reason,
+        let conf = match self.disallowed.get(&def_id) {
+            Some(&index) => &self.conf_disallowed[index],
             None => return,
         };
-        let func_path = cx.tcx.def_path_str(def_id);
-        let msg = format!("use of a disallowed method `{}`", func_path);
+        let msg = format!("use of a disallowed method `{}`", conf.path());
         span_lint_and_then(cx, DISALLOWED_METHODS, expr.span, &msg, |diag| {
-            if let Some(reason) = reason {
-                diag.note(reason);
+            if let conf::DisallowedMethod::WithReason {
+                reason: Some(reason), ..
+            } = conf
+            {
+                diag.note(&format!("{} (from clippy.toml)", reason));
             }
         });
     }

clippy_lints/src/utils/conf.rs

@@ -23,6 +23,14 @@ pub enum DisallowedMethod {
     WithReason { path: String, reason: Option<String> },
 }
 
+impl DisallowedMethod {
+    pub fn path(&self) -> &str {
+        let (Self::Simple(path) | Self::WithReason { path, .. }) = self;
+
+        path
+    }
+}
+
 /// A single disallowed type, used by the `DISALLOWED_TYPES` lint.
 #[derive(Clone, Debug, Deserialize)]
 #[serde(untagged)]

tests/ui-toml/toml_disallowed_methods/clippy.toml

@@ -1,6 +1,8 @@
 disallowed-methods = [
     # just a string is shorthand for path only
     "std::iter::Iterator::sum",
+    "f32::clamp",
+    "slice::sort_unstable",
     # can give path and reason with an inline table
     { path = "regex::Regex::is_match", reason = "no matching allowed" },
     # can use an inline table but omit reason

tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.rs

@@ -7,6 +7,11 @@ fn main() {
     let re = Regex::new(r"ab.*c").unwrap();
     re.is_match("abc");
 
-    let a = vec![1, 2, 3, 4];
+    let mut a = vec![1, 2, 3, 4];
     a.iter().sum::<i32>();
+
+    a.sort_unstable();
+
+    let _ = 2.0f32.clamp(3.0f32, 4.0f32);
+    let _ = 2.0f64.clamp(3.0f64, 4.0f64);
 }

tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.stderr

@@ -20,5 +20,17 @@ error: use of a disallowed method `std::iter::Iterator::sum`
 LL |     a.iter().sum::<i32>();
    |     ^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: use of a disallowed method `slice::sort_unstable`
+  --> $DIR/conf_disallowed_methods.rs:13:5
+   |
+LL |     a.sort_unstable();
+   |     ^^^^^^^^^^^^^^^^^
+
+error: use of a disallowed method `f32::clamp`
+  --> $DIR/conf_disallowed_methods.rs:15:13
+   |
+LL |     let _ = 2.0f32.clamp(3.0f32, 4.0f32);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors