compile error tests

tests/test_compile_error.rs

@@ -25,6 +25,7 @@ fn test_compile_errors() {
     t.compile_fail("tests/ui/invalid_closure.rs");
     t.compile_fail("tests/ui/pyclass_send.rs");
     t.compile_fail("tests/ui/invalid_argument_attributes.rs");
+    t.compile_fail("tests/ui/invalid_intopy_derive.rs");
     t.compile_fail("tests/ui/invalid_frompy_derive.rs");
     t.compile_fail("tests/ui/static_ref.rs");
     t.compile_fail("tests/ui/wrong_aspyref_lifetimes.rs");

tests/ui/invalid_intopy_derive.rs

@@ -0,0 +1,90 @@
+use pyo3::IntoPyObject;
+
+#[derive(IntoPyObject)]
+struct Foo();
+
+#[derive(IntoPyObject)]
+struct Foo2 {}
+
+#[derive(IntoPyObject)]
+enum EmptyEnum {}
+
+#[derive(IntoPyObject)]
+enum EnumWithEmptyTupleVar {
+    EmptyTuple(),
+    Valid(String),
+}
+
+#[derive(IntoPyObject)]
+enum EnumWithEmptyStructVar {
+    EmptyStruct {},
+    Valid(String),
+}
+
+#[derive(IntoPyObject)]
+#[pyo3(transparent)]
+struct EmptyTransparentTup();
+
+#[derive(IntoPyObject)]
+#[pyo3(transparent)]
+struct EmptyTransparentStruct {}
+
+#[derive(IntoPyObject)]
+enum EnumWithTransparentEmptyTupleVar {
+    #[pyo3(transparent)]
+    EmptyTuple(),
+    Valid(String),
+}
+
+#[derive(IntoPyObject)]
+enum EnumWithTransparentEmptyStructVar {
+    #[pyo3(transparent)]
+    EmptyStruct {},
+    Valid(String),
+}
+
+#[derive(IntoPyObject)]
+#[pyo3(transparent)]
+struct TransparentTupTooManyFields(String, String);
+
+#[derive(IntoPyObject)]
+#[pyo3(transparent)]
+struct TransparentStructTooManyFields {
+    foo: String,
+    bar: String,
+}
+
+#[derive(IntoPyObject)]
+enum EnumWithTransparentTupleTooMany {
+    #[pyo3(transparent)]
+    EmptyTuple(String, String),
+    Valid(String),
+}
+
+#[derive(IntoPyObject)]
+enum EnumWithTransparentStructTooMany {
+    #[pyo3(transparent)]
+    EmptyStruct {
+        foo: String,
+        bar: String,
+    },
+    Valid(String),
+}
+
+#[derive(IntoPyObject)]
+#[pyo3(unknown = "should not work")]
+struct UnknownContainerAttr {
+    a: String,
+}
+
+#[derive(IntoPyObject)]
+union Union {
+    a: usize,
+}
+
+#[derive(IntoPyObject)]
+enum UnitEnum {
+    Unit,
+}
+
+fn main() {}

tests/ui/invalid_intopy_derive.stderr

@@ -0,0 +1,105 @@
+error: cannot derive `IntoPyObject` for empty structs and variants
+ --> tests/ui/invalid_intopy_derive.rs:4:11
+  |
+4 | struct Foo();
+  |           ^^
+
+error: cannot derive `IntoPyObject` for empty structs and variants
+ --> tests/ui/invalid_intopy_derive.rs:7:13
+  |
+7 | struct Foo2 {}
+  |             ^^
+
+error: cannot derive `IntoPyObject` for empty enum
+  --> tests/ui/invalid_intopy_derive.rs:10:6
+   |
+10 | enum EmptyEnum {}
+   |      ^^^^^^^^^
+
+error: cannot derive `IntoPyObject` for empty structs and variants
+  --> tests/ui/invalid_intopy_derive.rs:14:15
+   |
+14 |     EmptyTuple(),
+   |               ^^
+
+error: cannot derive `IntoPyObject` for empty structs and variants
+  --> tests/ui/invalid_intopy_derive.rs:20:17
+   |
+20 |     EmptyStruct {},
+   |                 ^^
+
+error: cannot derive `IntoPyObject` for empty structs and variants
+  --> tests/ui/invalid_intopy_derive.rs:26:27
+   |
+26 | struct EmptyTransparentTup();
+   |                           ^^
+
+error: cannot derive `IntoPyObject` for empty structs and variants
+  --> tests/ui/invalid_intopy_derive.rs:30:31
+   |
+30 | struct EmptyTransparentStruct {}
+   |                               ^^
+
+error: cannot derive `IntoPyObject` for empty structs and variants
+  --> tests/ui/invalid_intopy_derive.rs:35:15
+   |
+35 |     EmptyTuple(),
+   |               ^^
+
+error: cannot derive `IntoPyObject` for empty structs and variants
+  --> tests/ui/invalid_intopy_derive.rs:42:17
+   |
+42 |     EmptyStruct {},
+   |                 ^^
+
+error: transparent structs and variants can only have 1 field
+  --> tests/ui/invalid_intopy_derive.rs:48:35
+   |
+48 | struct TransparentTupTooManyFields(String, String);
+   |                                   ^^^^^^^^^^^^^^^^
+
+error: transparent structs and variants can only have 1 field
+  --> tests/ui/invalid_intopy_derive.rs:52:39
+   |
+52 |   struct TransparentStructTooManyFields {
+   |  _______________________________________^
+53 | |     foo: String,
+54 | |     bar: String,
+55 | | }
+   | |_^
+
+error: transparent structs and variants can only have 1 field
+  --> tests/ui/invalid_intopy_derive.rs:60:15
+   |
+60 |     EmptyTuple(String, String),
+   |               ^^^^^^^^^^^^^^^^
+
+error: transparent structs and variants can only have 1 field
+  --> tests/ui/invalid_intopy_derive.rs:67:17
+   |
+67 |       EmptyStruct {
+   |  _________________^
+68 | |         foo: String,
+69 | |         bar: String,
+70 | |     },
+   | |_____^
+
+error: expected `transparent` or `crate`
+  --> tests/ui/invalid_intopy_derive.rs:75:8
+   |
+75 | #[pyo3(unknown = "should not work")]
+   |        ^^^^^^^
+
+error: #[derive(`IntoPyObject`)] is not supported for unions
+  --> tests/ui/invalid_intopy_derive.rs:81:1
+   |
+81 | union Union {
+   | ^^^^^
+
+error: cannot derive `IntoPyObject` for empty structs and variants
+  --> tests/ui/invalid_intopy_derive.rs:85:10
+   |
+85 | #[derive(IntoPyObject)]
+   |          ^^^^^^^^^^^^
+   |
+   = note: this error originates in the derive macro `IntoPyObject` (in Nightly builds, run with -Z macro-backtrace for more info)