1 files changed, 32 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0312.md b/compiler/rustc_error_codes/src/error_codes/E0312.md
new file mode 100644
index 000000000..c5f7cf2e3
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0312.md
@@ -0,0 +1,32 @@
+#### Note: this error code is no longer emitted by the compiler.
+
+Reference's lifetime of borrowed content doesn't match the expected lifetime.
+
+Erroneous code example:
+
+```compile_fail
+pub fn opt_str<'a>(maybestr: &'a Option<String>) -> &'static str {
+    if maybestr.is_none() {
+        "(none)"
+    } else {
+        let s: &'a str = maybestr.as_ref().unwrap();
+        s  // Invalid lifetime!
+    }
+}
+```
+
+To fix this error, either lessen the expected lifetime or find a way to not have
+to use this reference outside of its current scope (by running the code directly
+in the same block for example?):
+
+```
+// In this case, we can fix the issue by switching from "static" lifetime to 'a
+pub fn opt_str<'a>(maybestr: &'a Option<String>) -> &'a str {
+    if maybestr.is_none() {
+        "(none)"
+    } else {
+        let s: &'a str = maybestr.as_ref().unwrap();
+        s  // Ok!
+    }
+}
+```