apply suggestions

Author: dingxiangfei2009

src/const_eval.md

@@ -43,8 +43,9 @@ r[const-eval.const-expr.path-item]
 
 r[const-eval.const-expr.path-static]
 * Paths to [statics] with these restrictions and observations.
-  * If the evaluation is carried out in an initializer of a `const` item, or inside a `const` block, reads and writes to any `static mut` or [`extern` statics] are not allowed.
-  * If the evaluation is carried out in an initializer of a `static` item, reads into a `static`, or inside `unsafe` blocks reads into `static mut` are allowed. Reads and writes to `extern` statics are still not allowed.
+  * Reads and writes to `extern` statics are not allowed in any constant evaluation context.
+  * If the evaluation is carried out in an initializer of a `static` item, then *writes* into mutable `static` are not allowed, such as `static mut`s and `static`s containing an interior-mutable type.
+  * If the evaluation is *not* carried out in an initializer of a `static` item, then reads and writes to any mutable `static`, such as `static mut`s and `static`s containing an interior-mutable type.
 
 r[const-eval.const-expr.tuple]
 * [Tuple expressions].