const expression can borrow static items

Author: dingxiangfei2009

src/items/constant-items.md

@@ -91,6 +91,32 @@ m!(const _: () = (););
 // const _: () = ();
 ```
 
+## Use and reference to `static` items
+
+When a constant item or constant block is defined, [`static` items] can be used, borrowed or taken address of.
+By extension, you are allowed to call methods that immutably borrows the `static` items as receivers.
+
+```rust
+static A: u32 = 32;
+const ANOTHER_A: u32 = A;
+const BORROW_A: &'static u32 = &A;
+const POINTER_TO_A: *const u32 = &A as _;
+
+struct MyStruct {
+    inner: u32,
+}
+impl MyStruct {
+    const fn get(&self) -> u32 {
+        self.inner + 1
+    }
+}
+static MYSTRUCT: MyStruct = MyStruct {
+    inner: 0
+};
+const BORROW_STATIC_INNER: &'static u32 = &MYSTRUCT.inner;
+const CALL_CONST_STATIC_ASSOCIATED_METHOD: u32 = MYSTRUCT.get();
+```
+
 ## Evaluation
 
 [Free][free] constants are always [evaluated][const_eval] at compile-time to surface
@@ -111,6 +137,7 @@ fn unused_generic_function<T>() {
 [constant value]: ../const_eval.md#constant-expressions
 [free]: ../glossary.md#free-item
 [static lifetime elision]: ../lifetime-elision.md#static-lifetime-elision
+[`static` items]: ./static-items.md
 [trait definition]: traits.md
 [IDENTIFIER]: ../identifiers.md
 [underscore imports]: use-declarations.md#underscore-imports

src/items/static-items.md

@@ -22,11 +22,8 @@ Static initializers may refer to other statics.
 Non-`mut` static items that contain a type that is not [interior mutable] may
 be placed in read-only memory.
 
-All access to a static is safe, but there are a number of restrictions on
-statics:
-
-* The type must have the `Sync` trait bound to allow thread-safe access.
-* Constants cannot refer to statics.
+All access to a static is safe,
+provided that the type must have the `Sync` trait bound to allow thread-safe access.
 
 The initializer expression must be omitted in an [external block], and must be
 provided for free static items.
@@ -131,7 +128,7 @@ It can be confusing whether or not you should use a constant item or a static
 item. Constants should, in general, be preferred over statics unless one of the
 following are true:
 
-* Large amounts of data are being stored
+* Large amounts of data are being stored.
 * The single-address property of statics is required.
 * Interior mutability is required.