Warning on conflicting default_features keys

Signed-off-by: hi-rustin <rustin.liu@gmail.com>

src/cargo/util/toml/mod.rs

@@ -1922,6 +1922,13 @@ impl<P: ResolveToPath> DetailedTomlDependency<P> {
 
         let version = self.version.as_deref();
         let mut dep = Dependency::parse(pkg_name, version, new_source_id)?;
+        if self.default_features.is_some() && self.default_features2.is_some() {
+            cx.warnings.push(format!(
+                "found both `default-features` and `default_features` are set \
+                 in the `{}` dependency",
+                name_in_toml
+            ));
+        }
         dep.set_features(self.features.iter().flatten())
             .set_default_features(
                 self.default_features

tests/testsuite/features.rs

@@ -2067,3 +2067,42 @@ Caused by:
         )
         .run();
 }
+
+#[cargo_test]
+fn default_features_conflicting_warning() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+                authors = []
+
+                [dependencies]
+                a = { path = "a", features = ["f1"], default-features = false, default_features = false }
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file(
+            "a/Cargo.toml",
+            r#"
+                [package]
+                name = "a"
+                version = "0.1.0"
+                authors = []
+
+                [features]
+                default = ["f1"]
+                f1 = []
+            "#,
+        )
+        .file("a/src/lib.rs", "")
+        .build();
+
+    p.cargo("build")
+        .with_stderr_contains(
+            "[WARNING] found both `default-features` and `default_features` are set in the `a` dependency",
+        )
+            .run();
+}