rustc_lint_defs: Eliminate the dependency on `rustc_hir` for `Namespace`

`rustc_lint_defs` uses `rustc_hir` solely for the `Namespace` type,
which it only needs the static description from. Use the static
description directly, to eliminate the dependency on `rustc_hir`.

This reduces a long dependency chain:
- Many things depend on `rustc_errors`
- `rustc_errors` depends on `rustc_lint_defs`
- `rustc_lint_defs` depended on `rustc_hir` prior to this commit
- `rustc_hir` depends on `rustc_target`

3 files changed, 8 insertions, 7 deletions

diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index c485e6fc849..f26e5f05e1a 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -732,7 +732,7 @@ lint_pattern_in_foreign = patterns aren't allowed in foreign function declaratio
 lint_private_extern_crate_reexport = extern crate `{$ident}` is private and cannot be re-exported
     .suggestion = consider making the `extern crate` item publicly accessible
 
-lint_proc_macro_derive_resolution_fallback = cannot find {$ns} `{$ident}` in this scope
+lint_proc_macro_derive_resolution_fallback = cannot find {$ns_descr} `{$ident}` in this scope
     .label = names from parent modules are not accessible without an explicit import
 
 lint_query_instability = using `{$query}` can result in unstable query results
diff --git a/compiler/rustc_lint/src/early/diagnostics.rs b/compiler/rustc_lint/src/early/diagnostics.rs
index 678d3d1f8ed..0e283ed923a 100644
--- a/compiler/rustc_lint/src/early/diagnostics.rs
+++ b/compiler/rustc_lint/src/early/diagnostics.rs
@@ -64,10 +64,12 @@ pub fn decorate_builtin_lint(
             }
             .decorate_lint(diag);
         }
-        BuiltinLintDiag::ProcMacroDeriveResolutionFallback { span: macro_span, ns, ident } => {
-            lints::ProcMacroDeriveResolutionFallback { span: macro_span, ns, ident }
-                .decorate_lint(diag)
-        }
+        BuiltinLintDiag::ProcMacroDeriveResolutionFallback {
+            span: macro_span,
+            ns_descr,
+            ident,
+        } => lints::ProcMacroDeriveResolutionFallback { span: macro_span, ns_descr, ident }
+            .decorate_lint(diag),
         BuiltinLintDiag::MacroExpandedMacroExportsAccessedByAbsolutePaths(span_def) => {
             lints::MacroExpandedMacroExportsAccessedByAbsolutePaths { definition: span_def }
                 .decorate_lint(diag)
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index a6d59af6900..a1e26bf1503 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -8,7 +8,6 @@ use rustc_errors::{
     EmissionGuarantee, LintDiagnostic, MultiSpan, Subdiagnostic, SuggestionStyle,
 };
 use rustc_hir as hir;
-use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::VisitorExt;
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
@@ -2769,7 +2768,7 @@ pub(crate) struct AbsPathWithModuleSugg {
 pub(crate) struct ProcMacroDeriveResolutionFallback {
     #[label]
     pub span: Span,
-    pub ns: Namespace,
+    pub ns_descr: &'static str,
     pub ident: Ident,
 }