Add translatable diagnostic for invalid imports

compiler/rustc_resolve/messages.ftl

@@ -265,3 +265,6 @@ resolve_variable_bound_with_different_mode =
 
 resolve_change_import_binding =
     you can use `as` to change the binding name of the import
+
+resolve_imports_cannot_refer_to =
+    imports cannot refer to {$what}

compiler/rustc_resolve/src/errors.rs

@@ -605,3 +605,11 @@ pub(crate) struct ChangeImportBindingSuggestion {
     pub(crate) span: Span,
     pub(crate) suggestion: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(resolve_imports_cannot_refer_to)]
+pub(crate) struct ImportsCannotReferTo<'a> {
+    #[primary_span]
+    pub(crate) span: Span,
+    pub(crate) what: &'a str,
+}

compiler/rustc_resolve/src/late.rs

@@ -6,6 +6,7 @@
 //! If you wonder why there's no `early.rs`, that's because it's split into three files -
 //! `build_reduced_graph.rs`, `macros.rs` and `imports.rs`.
 
+use crate::errors::ImportsCannotReferTo;
 use crate::BindingKey;
 use crate::{path_names_to_string, rustdoc, BindingError, Finalize, LexicalScopeBinding};
 use crate::{Module, ModuleOrUniformRoot, NameBinding, ParentScope, PathResult};
@@ -2244,12 +2245,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                 _ => &[TypeNS],
             };
             let report_error = |this: &Self, ns| {
-                let what = if ns == TypeNS { "type parameters" } else { "local variables" };
                 if this.should_report_errs() {
-                    this.r
-                        .tcx
-                        .sess
-                        .span_err(ident.span, format!("imports cannot refer to {}", what));
+                    let what = if ns == TypeNS { "type parameters" } else { "local variables" };
+
+                    let err = ImportsCannotReferTo { span: ident.span, what };
+                    this.r.tcx.sess.create_err(err).emit();
                 }
             };