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diff --git a/compiler/rustc_error_codes/src/error_codes/E0688.md b/compiler/rustc_error_codes/src/error_codes/E0688.md
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+#### Note: this error code is no longer emitted by the compiler.
+
+In-band lifetimes were mixed with explicit lifetime binders.
+
+Erroneous code example:
+
+```ignore (feature got removed)
+#![feature(in_band_lifetimes)]
+
+fn foo<'a>(x: &'a u32, y: &'b u32) {}   // error!
+
+struct Foo<'a> { x: &'a u32 }
+
+impl Foo<'a> {
+    fn bar<'b>(x: &'a u32, y: &'b u32, z: &'c u32) {}   // error!
+}
+
+impl<'b> Foo<'a> {  // error!
+    fn baz() {}
+}
+```
+
+In-band lifetimes cannot be mixed with explicit lifetime binders.
+For example:
+
+```
+fn foo<'a, 'b>(x: &'a u32, y: &'b u32) {}   // ok!
+
+struct Foo<'a> { x: &'a u32 }
+
+impl<'a> Foo<'a> {
+    fn bar<'b,'c>(x: &'a u32, y: &'b u32, z: &'c u32) {}    // ok!
+}
+
+impl<'a> Foo<'a> {  // ok!
+    fn baz() {}
+}
+```