fix(toml): Prevent workspace=false in API

Author: epage

src/cargo/util/toml/schema.rs

@@ -411,7 +411,19 @@ impl<'de> de::Deserialize<'de> for InheritableBtreeMap {
 #[serde(rename_all = "kebab-case")]
 pub struct TomlInheritedField {
     #[serde(deserialize_with = "bool_no_false")]
-    pub workspace: bool,
+    workspace: bool,
+}
+
+impl TomlInheritedField {
+    pub fn new() -> Self {
+        TomlInheritedField { workspace: true }
+    }
+}
+
+impl Default for TomlInheritedField {
+    fn default() -> Self {
+        Self::new()
+    }
 }
 
 fn bool_no_false<'de, D: de::Deserializer<'de>>(deserializer: D) -> Result<bool, D::Error> {