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+A `repr(transparent)` type was also annotated with other, incompatible
+representation hints.
+
+Erroneous code example:
+
+```compile_fail,E0692
+#[repr(transparent, C)] // error: incompatible representation hints
+struct Grams(f32);
+```
+
+A type annotated as `repr(transparent)` delegates all representation concerns to
+another type, so adding more representation hints is contradictory. Remove
+either the `transparent` hint or the other hints, like this:
+
+```
+#[repr(transparent)]
+struct Grams(f32);
+```
+
+Alternatively, move the other attributes to the contained type:
+
+```
+#[repr(C)]
+struct Foo {
+    x: i32,
+    // ...
+}
+
+#[repr(transparent)]
+struct FooWrapper(Foo);
+```
+
+Note that introducing another `struct` just to have a place for the other
+attributes may have unintended side effects on the representation:
+
+```
+#[repr(transparent)]
+struct Grams(f32);
+
+#[repr(C)]
+struct Float(f32);
+
+#[repr(transparent)]
+struct Grams2(Float); // this is not equivalent to `Grams` above
+```
+
+Here, `Grams2` is a not equivalent to `Grams` -- the former transparently wraps
+a (non-transparent) struct containing a single float, while `Grams` is a
+transparent wrapper around a float. This can make a difference for the ABI.