Allow #[serde(default)] on tuple structs

test_suite/tests/ui/default-attribute/tuple_struct_path.rs

@@ -0,0 +1,77 @@
+use serde_derive::Deserialize;
+
+fn d<T>() -> T {
+    unimplemented!()
+}
+
+/// No errors expected:
+/// - if both fields are provided, both gets value from data
+/// - if only one field is provided, the second gets default value
+#[derive(Deserialize)]
+struct T1(u8, #[serde(default = "d")] u8);
+
+/// Errors expected -- the first field can get default value only if sequence is
+/// empty, but that mean that all other fields cannot be deserialized without
+/// errors, so the `#[serde(default)]` attribute is superfluous
+#[derive(Deserialize)]
+struct T2(#[serde(default = "d")] u8, u8, u8);
+
+/// No errors expected:
+/// - if both fields are provided, both gets value from data
+/// - if only one field is provided, the second gets default value
+/// - if none fields are provided, both gets default value
+#[derive(Deserialize)]
+struct T3(#[serde(default = "d")] u8, #[serde(default = "d")] u8);
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T1D(#[serde(default = "d")] u8, u8);
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T2D(u8, #[serde(default = "d")] u8);
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T3D(#[serde(default = "d")] u8, #[serde(default = "d")] u8);
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T1Path(#[serde(default)] u8, u8);
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T2Path(u8, #[serde(default)] u8);
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T3Path(#[serde(default)] u8, #[serde(default)] u8);
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T1PathD(#[serde(default = "d")] u8, u8);
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T2PathD(u8, #[serde(default = "d")] u8);
+
+/// No errors expected -- missing fields gets default values
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T3PathD(#[serde(default = "d")] u8, #[serde(default = "d")] u8);
+
+fn main() {}