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+A module cannot be found and therefore, the visibility cannot be determined.
+
+Erroneous code example:
+
+```compile_fail,E0578,edition2018
+foo!();
+
+pub (in ::Sea) struct Shark; // error!
+
+fn main() {}
+```
+
+Because of the call to the `foo` macro, the compiler guesses that the missing
+module could be inside it and fails because the macro definition cannot be
+found.
+
+To fix this error, please be sure that the module is in scope:
+
+```edition2018
+pub mod Sea {
+    pub (in crate::Sea) struct Shark;
+}
+
+fn main() {}
+```