Added long error description & modifed error_codes.rs

1 files changed, 22 insertions, 0 deletions

diff --git a/src/librustc_error_codes/error_codes/E0637.md b/src/librustc_error_codes/error_codes/E0637.md
new file mode 100644
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+++ b/src/librustc_error_codes/error_codes/E0637.md
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+The underscore `_` character has been used as the identifier for a lifetime. 
+
+Erroneous code example:
+```
+fn some_function<'_>(x: &'_ str, y: &'_ str) -> &'_ str {
+    //Some code
+}
+```
+
+Lifetimes are named with 'ident, where ident is the name of the 
+lifetime or loop. The `_` character, which represents the ignore pattern, 
+cannot be used because it is a reserved lifetime name. 
+To fix this, use a single lowercase letter as the 
+lifetime identifier, such as `'a`. For more information, see [The Rust Book](https://doc.rust-lang.org/stable/book/appendix-02-operators.html#non-operator-symbols).
+
+Corrected code example:
+```
+fn some_function<'a>(x: &'a str, y: &'a str) -> &'a str {
+    //Some code
+}
+```
+