apply suggestions

Author: dingxiangfei2009

src/const_eval.md

@@ -42,13 +42,16 @@ r[const-eval.const-expr.path-item]
   Recursively defining constants is not allowed.
 
 r[const-eval.const-expr.path-static]
-* Paths to [statics] with these restrictions and observations.
+* Paths to [statics] with these restrictions.
   * Writes to `static` items are not allowed in any constant evaluation context.
   * Reads from `extern` statics are not allowed in any constant evaluation context.
   * If the evaluation is *not* carried out in an initializer of a `static` item,
     then reads from any mutable `static` are not allowed.
     A mutable `static` is a `static mut` item, or a `static` item with an interior-mutable type.
 
+These requirements are checked only when the constant is evaluated.
+In other words, having such accessed syntactically occur in const contexts is allowed as long as they never get executed.
+
 r[const-eval.const-expr.tuple]
 * [Tuple expressions].