Avoid to suggest pattern match on the similarly named in fn signature

Author: chenyukang

compiler/rustc_passes/src/liveness.rs

@@ -1691,7 +1691,10 @@ impl<'tcx> Liveness<'_, 'tcx> {
                 if ln == self.exit_ln { false } else { self.assigned_on_exit(ln, var) };
 
             let mut typo = None;
-            for (hir_id, _, span) in &hir_ids_and_spans {
+            let filtered_hir_ids_and_spans = hir_ids_and_spans.iter().filter(|(hir_id, ..)| {
+                !matches!(self.ir.tcx.parent_hir_node(*hir_id), hir::Node::Param(_))
+            });
+            for (hir_id, _, span) in filtered_hir_ids_and_spans.clone() {
                 let ty = self.typeck_results.node_type(*hir_id);
                 if let ty::Adt(adt, _) = ty.peel_refs().kind() {
                     let name = Symbol::intern(&name);
@@ -1717,7 +1720,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
                 }
             }
             if typo.is_none() {
-                for (hir_id, _, span) in &hir_ids_and_spans {
+                for (hir_id, _, span) in filtered_hir_ids_and_spans {
                     let ty = self.typeck_results.node_type(*hir_id);
                     // Look for consts of the same type with similar names as well, not just unit
                     // structs and variants.

tests/ui/fn/invalid-sugg-for-unused-fn-arg-147303.rs

@@ -0,0 +1,13 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/147303>.
+
+#![deny(unused_assignments, unused_variables)]
+
+mod m1 {
+    const _MAX_FMTVER_X1X_EVENTNUM: i32 = 0;
+}
+
+mod m2 {
+    fn fun(rough: i32) {} //~ERROR unused variable
+}
+
+fn main() {}

tests/ui/fn/invalid-sugg-for-unused-fn-arg-147303.stderr

@@ -0,0 +1,14 @@
+error: unused variable: `rough`
+  --> $DIR/invalid-sugg-for-unused-fn-arg-issue-147303.rs:11:12
+   |
+LL |     fn fun(rough: i32) {}
+   |            ^^^^^ help: if this is intentional, prefix it with an underscore: `_rough`
+   |
+note: the lint level is defined here
+  --> $DIR/invalid-sugg-for-unused-fn-arg-issue-147303.rs:4:29
+   |
+LL | #![deny(unused_assignments, unused_variables)]
+   |                             ^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/lint/non-snake-case/lint-uppercase-variables.stderr

@@ -58,16 +58,7 @@ warning: unused variable: `Foo`
   --> $DIR/lint-uppercase-variables.rs:33:17
    |
 LL |     fn in_param(Foo: foo::Foo) {}
-   |                 ^^^
-   |
-help: if this is intentional, prefix it with an underscore
-   |
-LL |     fn in_param(_Foo: foo::Foo) {}
-   |                 +
-help: you might have meant to pattern match on the similarly named variant `Foo`
-   |
-LL |     fn in_param(foo::Foo::Foo: foo::Foo) {}
-   |                 ++++++++++
+   |                 ^^^ help: if this is intentional, prefix it with an underscore: `_Foo`
 
 error: structure field `X` should have a snake case name
   --> $DIR/lint-uppercase-variables.rs:10:5