Rollup merge of #96086 - jsgf:remove-extern-location, r=davidtwco

Remove `--extern-location` and all associated code

`--extern-location` was an experiment to investigate the best way to
generate useful diagnostics for unused dependency warnings by enabling a
build system to identify the corresponding build config.

While I did successfully use this, I've since been convinced the
alternative `--json unused-externs` mechanism is the way to go, and
there's no point in having two mechanisms with basically the same
functionality.

This effectively reverts https://github.com/rust-lang/rust/pull/72603

1 files changed, 1 insertions, 26 deletions

diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 152c53dac7f..0ffa65b79b5 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -33,8 +33,7 @@ use rustc_middle::middle::stability;
 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, RegisteredTools, Ty, TyCtxt};
-use rustc_serialize::json::Json;
-use rustc_session::lint::{BuiltinLintDiagnostics, ExternDepSpec};
+use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
 use rustc_session::Session;
 use rustc_span::lev_distance::find_best_match_for_name;
@@ -728,30 +727,6 @@ pub trait LintContext: Sized {
                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
                     db.span_label(span, "the attribute is introduced here");
                 }
-                BuiltinLintDiagnostics::ExternDepSpec(krate, loc) => {
-                    let json = match loc {
-                        ExternDepSpec::Json(json) => {
-                            db.help(&format!("remove unnecessary dependency `{}`", krate));
-                            json
-                        }
-                        ExternDepSpec::Raw(raw) => {
-                            db.help(&format!("remove unnecessary dependency `{}` at `{}`", krate, raw));
-                            db.span_suggestion_with_style(
-                                DUMMY_SP,
-                                "raw extern location",
-                                raw.clone(),
-                                Applicability::Unspecified,
-                                SuggestionStyle::CompletelyHidden,
-                            );
-                            Json::String(raw)
-                        }
-                    };
-                    db.tool_only_suggestion_with_metadata(
-                        "json extern location",
-                        Applicability::Unspecified,
-                        json
-                    );
-                }
                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
                     db.note(&note);
                 }