don't lint unnamed constants in missing_docs_in_private_items

Author: y21

clippy_lints/src/missing_doc.rs

@@ -17,6 +17,7 @@ use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::ty::Visibility;
 use rustc_session::impl_lint_pass;
 use rustc_span::def_id::CRATE_DEF_ID;
+use rustc_span::symbol::kw;
 use rustc_span::{Span, sym};
 
 declare_clippy_lint! {
@@ -184,8 +185,12 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
                     }
                 }
             },
-            hir::ItemKind::Const(..)
-            | hir::ItemKind::Enum(..)
+            hir::ItemKind::Const(..) => {
+                if it.ident.name == kw::Underscore {
+                    note_prev_span_then_ret!(self.prev_span, it.span);
+                }
+            },
+            hir::ItemKind::Enum(..)
             | hir::ItemKind::Macro(..)
             | hir::ItemKind::Mod(..)
             | hir::ItemKind::Static(..)

tests/ui/missing_doc.rs

@@ -116,6 +116,9 @@ with_span!(span pub fn foo_pm() {});
 with_span!(span pub static FOO_PM: u32 = 0;);
 with_span!(span pub const FOO2_PM: u32 = 0;);
 
+// Don't lint unnamed constants
+const _: () = ();
+
 // issue #12197
 // Undocumented field originated inside of spanned proc-macro attribute
 /// Some dox for struct.