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+A non-constant value was used in a constant expression.
+
+Erroneous code example:
+
+```compile_fail,E0435
+let foo = 42;
+let a: [u8; foo]; // error: attempt to use a non-constant value in a constant
+```
+
+'constant' means 'a compile-time value'.
+
+More details can be found in the [Variables and Mutability] section of the book.
+
+[Variables and Mutability]: https://doc.rust-lang.org/book/ch03-01-variables-and-mutability.html#differences-between-variables-and-constants
+
+To fix this error, please replace the value with a constant. Example:
+
+```
+let a: [u8; 42]; // ok!
+```
+
+Or:
+
+```
+const FOO: usize = 42;
+let a: [u8; FOO]; // ok!
+```