const-eval.const-expr.borrows: mention indirect places

Author: RalfJung

src/const_eval.md

@@ -83,9 +83,10 @@ r[const-eval.const-expr.builtin-arith-logic]
 r[const-eval.const-expr.borrows]
 * All forms of [borrow]s, including raw borrows, with one limitation:
   mutable borrows and shared borrows to values with interior mutability
-  are only allowed to refer to *transient* places or to *static* places. A place is *transient*
-  if its lifetime is strictly contained inside the current [const context].
-  A place is *static* if it is a `static` item or a [promoted expression].
+  are only allowed to refer to *transient* places, to *indirect* places, or to *static* places.
+  A place is *transient* if it is based on a local variable whose lifetime is strictly contained inside the current [const context].
+  A place is *indirect* if it is based on a [dereference expression][dereference operator].
+  A place is *static* if it is based on a `static` item or a [promoted expression].
 
 r[const-eval.const-expr.deref]
 * The [dereference operator] except for raw pointers.