move E0623 into the new error code format

1 files changed, 41 insertions, 0 deletions

diff --git a/src/librustc_error_codes/error_codes/E0623.md b/src/librustc_error_codes/error_codes/E0623.md
new file mode 100644
index 00000000000..1290edd0a0e
--- /dev/null
+++ b/src/librustc_error_codes/error_codes/E0623.md
@@ -0,0 +1,41 @@
+A lifetime didn't match what was expected.
+
+Erroneous code example:
+
+```compile_fail,E0623
+struct Foo<'a> {
+    x: &'a isize,
+}
+
+fn bar<'short, 'long>(c: Foo<'short>, l: &'long isize) {
+    let _: Foo<'long> = c; // error!
+}
+```
+
+In this example, we tried to set a value with an incompatible lifetime to
+another one (`'long` is unrelated to `'short`). We can solve this issue in
+two different ways:
+
+Either we make `'short` live at least as long as `'long`:
+
+```
+struct Foo<'a> {
+    x: &'a isize,
+}
+
+// we set 'short to live at least as long as 'long
+fn bar<'short: 'long, 'long>(c: Foo<'short>, l: &'long isize) {
+    let _: Foo<'long> = c; // ok!
+}
+```
+
+Or we use only one lifetime:
+
+```
+struct Foo<'a> {
+    x: &'a isize,
+}
+fn bar<'short>(c: Foo<'short>, l: &'short isize) {
+    let _: Foo<'short> = c; // ok!
+}
+```