Fix bug with new feature resolver and required-features.

src/cargo/core/resolver/features.rs

@@ -194,8 +194,8 @@ impl ResolvedFeatures {
     }
 
     /// Variant of `activated_features` that returns an empty Vec if this is
-    /// not a valid pkg_id/is_build combination. Used by `cargo clean` which
-    /// doesn't know the exact set.
+    /// not a valid pkg_id/is_build combination. Used in places which do
+    /// not know which packages are activated (like `cargo clean`).
     pub fn activated_features_unverified(
         &self,
         pkg_id: PackageId,

src/cargo/ops/cargo_compile.rs

@@ -956,8 +956,8 @@ fn resolve_all_features(
             } else {
                 FeaturesFor::NormalOrDev
             };
-            for feature in resolved_features.activated_features(dep_id, features_for) {
-                features.insert(dep.name_in_toml().to_string() + "/" + &feature);
+            for feature in resolved_features.activated_features_unverified(dep_id, features_for) {
+                features.insert(format!("{}/{}", dep.name_in_toml(), feature));
             }
         }
     }

tests/testsuite/features2.rs

@@ -1,7 +1,7 @@
 //! Tests for the new feature resolver.
 
-use cargo_test_support::project;
 use cargo_test_support::registry::{Dependency, Package};
+use cargo_test_support::{basic_manifest, project};
 
 #[cargo_test]
 fn inactivate_targets() {
@@ -893,3 +893,41 @@ fn disabled_shared_build_dep() {
         .with_stdout("hello from somedep")
         .run();
 }
+
+#[cargo_test]
+fn required_features_inactive_dep() {
+    // required-features with an inactivated dep.
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            version = "0.1.0"
+
+            [target.'cfg(whatever)'.dependencies]
+            bar = {path="bar"}
+
+            [[bin]]
+            name = "foo"
+            required-features = ["feat1"]
+
+            [features]
+            feat1 = []
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .file("bar/Cargo.toml", &basic_manifest("bar", "0.1.0"))
+        .file("bar/src/lib.rs", "")
+        .build();
+
+    p.cargo("check -Zfeatures=itarget")
+        .masquerade_as_nightly_cargo()
+        .with_stderr("[FINISHED] [..]")
+        .run();
+
+    p.cargo("check -Zfeatures=itarget --features=feat1")
+        .masquerade_as_nightly_cargo()
+        .with_stderr("[CHECKING] foo[..]\n[FINISHED] [..]")
+        .run();
+}