Emit note when --future-incompat-report had nothing to report

Author: Aaron1011

src/cargo/core/compiler/job_queue.rs

@@ -807,9 +807,16 @@ impl<'cfg> DrainState<'cfg> {
     }
 
     fn emit_future_incompat(&mut self, cx: &mut Context<'_, '_>) {
-        if cx.bcx.config.cli_unstable().enable_future_incompat_feature
-            && !self.per_crate_future_incompat_reports.is_empty()
-        {
+        if cx.bcx.config.cli_unstable().enable_future_incompat_feature {
+            if self.per_crate_future_incompat_reports.is_empty() {
+                drop(
+                    cx.bcx
+                        .config
+                        .shell()
+                        .note("0 dependencies had future-incompat warnings"),
+                );
+                return;
+            }
             self.per_crate_future_incompat_reports
                 .sort_by_key(|r| r.package_id);
 

tests/testsuite/future_incompat_report.rs

@@ -51,6 +51,23 @@ fn gate_future_incompat_report() {
         .run();
 }
 
+#[cargo_test]
+fn test_zero_future_incompat() {
+    if !is_nightly() {
+        return;
+    }
+
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.0.0"))
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build --future-incompat-report -Z unstable-options -Z future-incompat-report")
+        .masquerade_as_nightly_cargo()
+        .with_stderr_contains("note: 0 dependencies had future-incompat warnings")
+        .run();
+}
+
 #[cargo_test]
 fn test_single_crate() {
     if !is_nightly() {