Emit the lint level of the unused-crate-dependencies

Also, turn off the lint when the unused dependencies json flag
is specified so that cargo doesn't have to supress the lint

3 files changed, 11 insertions, 9 deletions

diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index dbb71d52e49..2b6dec905f1 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -196,7 +196,7 @@ pub trait Emitter {
     fn emit_future_breakage_report(&mut self, _diags: Vec<(FutureBreakage, Diagnostic)>) {}
 
     /// Emit list of unused externs
-    fn emit_unused_externs(&mut self, _unused_externs: &[&str]) {}
+    fn emit_unused_externs(&mut self, _lint_level: &str, _unused_externs: &[&str]) {}
 
     /// Checks if should show explanations about "rustc --explain"
     fn should_show_explain(&self) -> bool {
diff --git a/compiler/rustc_errors/src/json.rs b/compiler/rustc_errors/src/json.rs
index a1ab98f766e..8511b51e3bf 100644
--- a/compiler/rustc_errors/src/json.rs
+++ b/compiler/rustc_errors/src/json.rs
@@ -159,8 +159,8 @@ impl Emitter for JsonEmitter {
         }
     }
 
-    fn emit_unused_externs(&mut self, unused_externs: &[&str]) {
-        let data = UnusedExterns { unused_extern_names: unused_externs };
+    fn emit_unused_externs(&mut self, lint_level: &str, unused_externs: &[&str]) {
+        let data = UnusedExterns { lint_level, unused_extern_names: unused_externs };
         let result = if self.pretty {
             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
         } else {
@@ -336,9 +336,11 @@ struct FutureIncompatReport {
 }
 
 #[derive(Encodable)]
-struct UnusedExterns<'a, 'b> {
+struct UnusedExterns<'a, 'b, 'c> {
+    /// The severity level of the unused dependencies lint
+    lint_level: &'a str,
     /// List of unused externs by their names.
-    unused_extern_names: &'a [&'b str],
+    unused_extern_names: &'b [&'c str],
 }
 
 impl Diagnostic {
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 5720e98abc8..533c32b32c6 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -767,8 +767,8 @@ impl Handler {
         self.inner.borrow_mut().emitter.emit_future_breakage_report(diags)
     }
 
-    pub fn emit_unused_externs(&self, unused_externs: &[&str]) {
-        self.inner.borrow_mut().emit_unused_externs(unused_externs)
+    pub fn emit_unused_externs(&self, lint_level: &str, unused_externs: &[&str]) {
+        self.inner.borrow_mut().emit_unused_externs(lint_level, unused_externs)
     }
 
     pub fn delay_as_bug(&self, diagnostic: Diagnostic) {
@@ -845,8 +845,8 @@ impl HandlerInner {
         self.emitter.emit_artifact_notification(path, artifact_type);
     }
 
-    fn emit_unused_externs(&mut self, unused_externs: &[&str]) {
-        self.emitter.emit_unused_externs(unused_externs);
+    fn emit_unused_externs(&mut self, lint_level: &str, unused_externs: &[&str]) {
+        self.emitter.emit_unused_externs(lint_level, unused_externs);
     }
 
     fn treat_err_as_bug(&self) -> bool {