Add tests for #[attr] if

Cargo.toml

@@ -78,6 +78,7 @@ auto_enums_derive = { version = "=0.7.2", path = "derive", default-features = fa
 
 [dev-dependencies]
 trybuild = "1.0"
+rustversion = "1.0"
 futures_crate = { version = "0.3", package = "futures" }
 rayon_crate = { version = "1.2", package = "rayon" }
 serde_crate = { version = "1.0", package = "serde" }

tests/auto_enum.rs

@@ -497,6 +497,11 @@ mod stable {
         }
         assert!(try_operator(None).unwrap_err().source().is_some());
     }
+
+    // This hack is needed until https://github.com/rust-lang/rust/pull/69201
+    // makes it way into stable.
+    #[rustversion::nightly]
+    include!("auto_enum_if_attr.rs.in");
 }
 
 // nightly
@@ -706,4 +711,22 @@ mod nightly {
             assert_eq!(marker2(i).clone().sum::<i32>(), *x - 1);
         }
     }
+
+    #[test]
+    fn non_stmt_expr() {
+        fn match_(x: bool) -> Option<impl Iterator<Item = u8>> {
+            Some(
+                #[auto_enum(Iterator)]
+                match x {
+                    true => std::iter::once(0),
+                    _ => std::iter::repeat(1),
+                },
+            )
+        }
+    }
+
+    // This hack is needed until https://github.com/rust-lang/rust/pull/69201
+    // makes it way into stable.
+    #[rustversion::nightly]
+    include!("auto_enum_if_attr_unstable.rs.in");
 }

tests/auto_enum_if_attr.rs.in

@@ -0,0 +1,23 @@
+// FIXME: Once https://github.com/rust-lang/rust/pull/69201 makes its
+// way into stable, move this back into `auto_enum.rs
+
+#[auto_enum]
+fn a(x: bool) -> impl Iterator<Item = u8> {
+    let res = {
+        #[auto_enum(Iterator)]
+        if x { std::iter::once(0) } else { std::iter::repeat(1) }
+    };
+    res
+}
+
+#[auto_enum(Iterator)]
+fn if_in_if(x: usize) -> impl Iterator<Item = i32> {
+    if x == 0 {
+        1..8
+    } else if x > 3 {
+        #[nested]
+        if x > 4 { 2..=10 } else { (11..20).map(|x| x - 1) }
+    } else {
+        (0..2).map(|x| x + 1)
+    }
+}

tests/auto_enum_if_attr_unstable.rs.in

@@ -0,0 +1,9 @@
+// FIXME: Once https://github.com/rust-lang/rust/pull/69201 makes its
+// way into stable, move this back into `auto_enum.rs
+
+fn if_(x: bool) -> Option<impl Iterator<Item = u8>> {
+    Some(
+        #[auto_enum(Iterator)]
+        if x { std::iter::once(0) } else { std::iter::repeat(1) },
+    )
+}

tests/ui/auto_enum/non-stmt-expr.rs

@@ -0,0 +1,22 @@
+use auto_enums::auto_enum;
+
+#[auto_enum]
+fn b(x: bool) -> Option<impl Iterator<Item = u8>> {
+    Some(
+        #[auto_enum(Iterator)]
+        if x { std::iter::once(0) } else { std::iter::repeat(1) },
+    )
+}
+
+#[auto_enum]
+fn c(x: bool) -> Option<impl Iterator<Item = u8>> {
+    Some(
+        #[auto_enum(Iterator)]
+        match x {
+            true => std::iter::once(0),
+            _ => std::iter::repeat(1),
+        },
+    )
+}
+
+fn main() {}

tests/ui/auto_enum/non-stmt-expr.stderr

@@ -0,0 +1,22 @@
+error: `#[auto_enum]` is required two or more branches or marker macros in total, there is no branch or marker macro in this statement
+ --> $DIR/non-stmt-expr.rs:4:1
+  |
+4 | / fn b(x: bool) -> Option<impl Iterator<Item = u8>> {
+5 | |     Some(
+6 | |         #[auto_enum(Iterator)]
+7 | |         if x { std::iter::once(0) } else { std::iter::repeat(1) },
+8 | |     )
+9 | | }
+  | |_^
+
+error: `#[auto_enum]` is required two or more branches or marker macros in total, there is no branch or marker macro in this statement
+  --> $DIR/non-stmt-expr.rs:12:1
+   |
+12 | / fn c(x: bool) -> Option<impl Iterator<Item = u8>> {
+13 | |     Some(
+14 | |         #[auto_enum(Iterator)]
+15 | |         match x {
+...  |
+19 | |     )
+20 | | }
+   | |_^

tests/ui/auto_enum/rejected-by-rustc.rs

@@ -10,16 +10,4 @@ fn wrong_if(x: usize) -> impl Iterator<Item = i32> {
     }
 }
 
-#[auto_enum(Iterator)]
-fn if_in_if(x: usize) -> impl Iterator<Item = i32> {
-    if x == 0 {
-        1..8
-    } else if x > 3 {
-        #[nested]
-        if x > 4 { 2..=10 } else { (11..20).map(|x| x - 1) }
-    } else {
-        (0..2).map(|x| x + 1)
-    }
-}
-
 fn main() {}