Document that prelude resolution happens in three different namespaces

Author: jyn514

src/names/preludes.md

@@ -146,11 +146,29 @@ r[names.preludes.precedence]
 ## Prelude precedence
 Names of items are resolved in the following order:
 
+Value namespace: only the standard library prelude contains items in this namespace.
+
+1. Explicit definitions (including imports)
+2. Standard library prelude
+
+Type namespace:
+
 1. Explicit definitions (including imports)
-2. Language and macro prelude. If an item is present in both preludes, an error is emitted.
-3. Extern prelude
-4. Tool prelude
-5. Standard library prelude
+2. Extern prelude
+3. Tool prelude
+4. Standard library prelude
+5. Language prelude
+
+Macro namespace:
+
+1. Explicit definitions (including imports)
+    1. [Derive helpers]
+    2. [Macros by example][macro_rules]
+2. Macro prelude
+3. Standard library prelude
+4. [Language prelude][Built-in attributes]
+
+Currently, the ordering between library and language is not observable because there are no items in both namespaces.
 
 r[names.preludes.no_implicit_prelude]
 ## The `no_implicit_prelude` attribute
@@ -171,6 +189,8 @@ r[names.preludes.no_implicit_prelude.edition2018]
 > Starting in the 2018 edition, it will remove the `macro_use` prelude.
 
 [`extern crate`]: ../items/extern-crates.md
+[macro_rules]: ../macros-by-example.md
+[Derive helpers]: ../names/scopes.html#derive-macro-helper-attributes
 [`macro_use` attribute]: ../macros-by-example.md#the-macro_use-attribute
 [`macro_use` prelude]: #macro_use-prelude
 [`no_std` attribute]: #the-no_std-attribute