make non_upper_case_globals lint not report trait impls

compiler/rustc_lint/src/nonstandard_style.rs

@@ -494,6 +494,15 @@ fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
             hir::ItemKind::Const(..) => {
                 NonUpperCaseGlobals::check_upper_case(cx, "constant", &it.ident);
             }
+            // we only want to check inherent associated consts, trait consts
+            // are linted at def-site.
+            hir::ItemKind::Impl(hir::Impl { of_trait: None, items, .. }) => {
+                for it in *items {
+                    if let hir::AssocItemKind::Const = it.kind {
+                        NonUpperCaseGlobals::check_upper_case(cx, "associated constant", &it.ident);
+                    }
+                }
+            }
             _ => {}
         }
     }
@@ -504,12 +513,6 @@ fn check_trait_item(&mut self, cx: &LateContext<'_>, ti: &hir::TraitItem<'_>) {
         }
     }
 
-    fn check_impl_item(&mut self, cx: &LateContext<'_>, ii: &hir::ImplItem<'_>) {
-        if let hir::ImplItemKind::Const(..) = ii.kind {
-            NonUpperCaseGlobals::check_upper_case(cx, "associated constant", &ii.ident);
-        }
-    }
-
     fn check_pat(&mut self, cx: &LateContext<'_>, p: &hir::Pat<'_>) {
         // Lint for constants that look like binding identifiers (#7526)
         if let PatKind::Path(hir::QPath::Resolved(None, ref path)) = p.kind {

tests/ui/lint/lint-non-uppercase-trait-assoc-const.rs

@@ -0,0 +1,15 @@
+#![deny(non_upper_case_globals)]
+
+trait Trait {
+    const item: usize;
+    //~^ ERROR associated constant `item` should have an upper case name [non_upper_case_globals]
+}
+
+struct Foo;
+
+impl Trait for Foo {
+    const item: usize = 5;
+    // ^^^ there should be no error here (in the trait `impl`)
+}
+
+fn main() {}

tests/ui/lint/lint-non-uppercase-trait-assoc-const.stderr

@@ -0,0 +1,14 @@
+error: associated constant `item` should have an upper case name
+  --> $DIR/lint-non-uppercase-trait-assoc-const.rs:4:11
+   |
+LL |     const item: usize;
+   |           ^^^^ help: convert the identifier to upper case: `ITEM`
+   |
+note: the lint level is defined here
+  --> $DIR/lint-non-uppercase-trait-assoc-const.rs:1:9
+   |
+LL | #![deny(non_upper_case_globals)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+