rewrite bullet points as prose

Author: yaahc

src/names/name-resolution.md

@@ -10,54 +10,117 @@ without conflict. Each name is valid within a [scope], or a region of source
 text where that name may be referenced. Access to certain names may be
 restricted based on their [visibility].
 
-* Names are resolved at three different stages of compilation.
-* [Macros] and [use declarations] are resolved during macro expansion.
-    * This stage of resolution is known as "Early Resolution".
-* `Type::assoc_item`, `<Type>::assoc_item`, `<Enum>::Variant` and `EnumTyAlias::Variant` are resolved during type checking
-    * `Trait::assoc_item`, `<Type as Trait>::assoc_item` and `Enum::Variant` are resolved during late resolution
-    * This stage of resolution is known as type-relative resolution.
-        * in reality this is never talked about so I doubt it has a name yet.
-* All other names are resolved during AST lowering.
-    * This stage of resolution is known as "Late Resolution".
-    * Note, late resolution occurs before type dependent resolution.
+Name resolution is split into three stages throughout the compilation process.
+The first stage, Expansion-time resolution, resolves all [use declarations] and
+[macro invocations]. The second stage, Primary resolution, resolves all names
+that have not yet been resolved that do not depend on type information to
+resolve. The last stage, Type-relative resolution, resolves the remaining names
+once type information is available.
+
+> Note
+>
+> * Expansion-time resolution is also known as "Early Resolution"
+> * Primary resolution is also known as "Late Resolution"
+
+r[names.resolution.expansion]
+## Expansion-time name resolution
+
+r[names.resolution.expansion.intro]
+
+Expansion-time name resolution is the stage of name resolution necessary to
+complete macro expansion and fully generate a crate's AST. This stage requires
+the resolution of macro invocations and use declarations. Resolving use
+declarations is required to resolve [path-based scope] macro invocations.
+Resolving macro invocations is required in order to expand them.
+
+The expansion process is iterative, alternately resolving imports, resolving
+and expanding macro invocations, then repeating until there are no further
+macros invocations to resolve. Once this process is completed all the imports
+are resolved again to ensure that the macro expansion process did not introduce
+any new ambiguious imports.
+
+TODO: do we want to talk about this? feels like an implementation detail but
+also really helps to understand certain kinds of ambiguity errors that users
+can run into.
+
+> Note
+>
+> This causes so called time traveling ambiguities, such as when a glob import introduces an item that is ambiguous with its own base path.
+>
+```rust
+macro_rules! m {
+    () => { mod bar {} }
+}
+
+mod bar {
+    pub(crate) use m;
+}
+
+fn f() {
+    // * initially speculatively resolve bar to the module in the crate root
+    // * expansion of m introduces a second bar module inside the body of f
+    // * expansion-time resolution finalizes resolutions by re-resolving all
+    //   imports and macro invocations, sees the introduced ambiguity
+    //   and reports it as an error
+    bar::m!(); // ERROR `bar` is ambiguous
+}
+```
+
+TODO I would like to be able to link to a path-based scope section that
+     discusses the various kinds of macros that can be invoked via path-based scope.
+     Right now the section I know of off of the top of my head lives in the macros
+     by example chapter.
+
+r[names.resolution.expansion.imports]
 
-r[names.resolution.early]
-## Early name resolution
+All use declarations are fully resolved during this stage of resolution.
+Type-relative paths cannot be resolved at this stage of compilation and will
+produce an error.
 
-r[names.resolution.early.intro]
+* `Type::assoc_item`, `<Type>::assoc_item`, `<Enum>::Variant` and `EnumTyAlias::Variant` are resolved during type checking
+    * `Trait::assoc_item`, `<Type as Trait>::assoc_item` and `Enum::Variant` are resolved during late resolution
 
-* early name resolution is the part of name resolution that happens during macro expansion
-* early name resolution includes the resolution of imports and macros
-* early name resolution is the minimum amount of resolution required to resolve macro invocations so they can be expanded.
-* resolving imports is necessary to resolve macro invocations
-    * specifically for path-based scope macro resolutions, this can occur
-      either because of a `#[macro_export]`, a proc macro definition, or a
-      reexport of a macro in 2018 or later code.
-* resolving macro invocations and tying them to macro declarations is necessary so they can be expanded
-* this process is iterative and repeats until there are no remaining unexpanded macro invocations (fixed point algorithm)
-* Post expansion these resolutions are checked again to ensure no new ambiguities were introduced by the expansion process
-  * This causes so called time traveling ambiguities, such as when a glob import introduces an item that is ambiguous with its own base path.
+```rust
+mod my_mod {
+    pub const Const: () = ();
 
-TODO Document some time traveling ambiguitie examples, place in relevant ambiguity section
+    pub enum MyEnum {
+        MyVariant
+    }
 
-r[names.resolution.early.imports]
+    impl MyEnum {
+        pub const Const: () = ();
+    }
 
-* All imports are fully resolved at this point.
-    * imports of names that cannot be fully resolved during macro expansion, such as those depending on type information, are not supported and will produce an error.
+    pub type TypeAlias = MyEnum;
+}
 
-TODO example of unsupported type dependent import
+fn foo() {
+    use my_mod::MyEnum; // OK
+    use my_mod::MyEnum::MyVariant; // OK
+    use my_mod::TypeAlias; // OK
+    use my_mod::TypeAlias::MyVariant; // Doesn't work
+    use my_mod::MyEnum::Const; // Doesn't work
+    use my_mod::Const; // OK
+    let _ = my_mod::TypeAlias::MyVariant; // OK
+    let _ = my_mod::MyEnum::Const; // OK
+}
+```
 
-r[names.resolution.early.imports.shadowing]
+r[names.resolution.expansion.imports.shadowing]
 
 The following is a list of situations where shadowing of use declarations is permitted:
 
 * [use glob shadowing]
 * [macro textual scope shadowing]
 
-r[names.resolution.early.imports.errors]
-r[names.resolution.early.imports.errors.ambiguity]
+r[names.resolution.expansion.imports.errors]
+r[names.resolution.expansion.imports.errors.ambiguity]
+
+TODO shadowing and ambiguity may or may not represent the same section or one may be a subsection of the other
 
-* shadowing and ambiguity may or may not represent the same section or one may be a subsection of the other
+The following is a list of situations where shadowing of use declarations is
+_NOT_ permitted, otherwise known as ambiguity errors:
 
 * Builtin Attributes
 * Derive Helpers
@@ -70,34 +133,26 @@ r[names.resolution.early.imports.errors.ambiguity]
 r[names.resolution.expansion.imports.errors.ambiguity]
 ## Ambiguities
 
-> [!NOTE]
-> This section is incomplete.
-
 r[items.use.ambiguities.intro]
-Some situations are an error when there is an ambiguity as to which name a `use` declaration refers. This happens when there are two name candidates that do not resolve to the same entity.
+Some situations are an error when there is an ambiguity as to which name a
+`use` declaration refers. This happens when there are two name candidates that
+do not resolve to the same entity where neither import is
+[permitted](names.resolution.expansion.imports.shadowing) to shadow the other.
 
-* except where shadowing is allowed
 r[names.resolution.early.imports.errors.ambiguity.globvsglob]
 * it is an error to name an item through ambiguous use declarations
- * two globs imports which both have an item matching that name where the items are different
-     * this is not an error even if is a third non glob binding resolution to an item with the same name
+    * two globs imports which both have an item matching that name where the items are different
+        * this is not an error even if is a third non glob binding resolution to an item with the same name
 * it is not an error to have two glob imports which include items which would be ambiguous so long as you do not name one of those items through the ambiguous glob imports
     * Should this live alongside use decls item page or in the name resolution page?
 
 r[items.use.ambiguities.glob]
-Glob imports are allowed to import conflicting names in the same namespace as long as the name is not used.
-For example:
+Glob imports are allowed to import conflicting names in the same namespace as
+long as the name is not used. Names may not be resolved through ambiguous glob
+statements. Conflicting names from ambiguous glob statements may still be
+shadowed and used without producing an error.
 
-TODO: move this section? It's documenting a situation that _isnt_ an ambiguity
-error. I've been working off of a pattern I think I saw in a few other
-locations, where we have specific error sections that document all of the
-reference relevant error cases associated with an some part of the language.
-    * This section does technically document globvsglob ambituity errors, but
-      it does so indirectly. We never explicitly mention "you can't resolve a
-      name through a glob import when there are multiple candidate glob imports
-      in scope that each resolve to different entities". We just say "you can
-      do that if you don't actually use the ambiguious names" and have an
-      example that shows that trying to use the name would be an error.
+For example:
 
 ```rust
 mod foo {
@@ -147,10 +202,11 @@ fn main() {
 ```
 
 r[names.resolution.early.imports.errors.ambiguity.builtin-attr]
-* it is an error to use a user defined attribute or derive macro with the same name as a builtin attribute (e.g. inline)
-    * I think we may special case this one and allow certain kinds of
-      ambiguities where the builtin-attr is shadowed by a user attribute (not
-      sure if this actually exists or is just proposed, TODO investigate)
+It is an error to use a user defined attribute or derive macro with the same
+name as a builtin attribute (e.g. inline)
+* I think we may special case this one and allow certain kinds of ambiguities
+  where the builtin-attr is shadowed by a user attribute (not sure if this
+  actually exists or is just proposed, TODO investigate)
 
 <!-- ignore: test doesn't support proc-macro -->
 ```rust,ignore
@@ -179,57 +235,50 @@ pub fn bar() {}
 pub fn baz() {}
 
 #[inline] // ERROR `inline` is ambiguous
-pub fn quix() {}
+pub fn qux() {}
+```
+
+r[names.resolution.early.imports.errors.ambiguity.pathvstextualmacro]
+Path-based scope bindings for macros may not shadow textual scope bindings to macros.
+
+```rust
+#[macro_export]
+macro_rules! m2 {
+    () => {}
+}
+macro_rules! m {
+    () => {}
+}
+pub fn foo() {
+    m!(); // ERROR `m` is ambiguous
+    use crate::m2 as m; // in scope for entire function body
+}
 ```
 
-r[names.resolution.early.imports.errors.ambiguity.textualvspathbasedscope]
-* path-based scope bindings for macros may not shadow textual scope bindings to macros
-    * This is sort of an intersection between macros and imports, because at
-      least in stable rust you can only get path-based macro resolutions from
-      imports of mbe macros (and presumably from proc macro crates), but you
-      can only get textual scope of macros from macro declarations
-    * https://doc.rust-lang.org/nightly/reference/names/namespaces.html#r-names.namespaces.sub-namespaces.use-shadow
-    * [macro.decl.scope.path.ambiguity]
 r[names.resolution.early.imports.errors.ambiguity.globvsouter]
-* it is an error to shadow an outer name binding with a glob import
-    * This seems to only apply to early resolution (duh, I documented this as part of an early resolution codepath)
-        *   // Below we report various ambiguity errors.
-            // We do not need to report them if we are either in speculative resolution,
-            // or in late resolution when everything is already imported and expanded
-            // and no ambiguities exist.
-    * I attempted to produce an example using structs and it allowed the outer import to shadow the inner glob just fine
+it is an error to shadow an outer name binding with a glob import.
 
 ```rust
 mod bar {
-    pub struct Name;
+    pub mod foo {
+        pub struct Name;
+    }
 }
 
 mod baz {
-    pub struct Name;
+    pub mod foo {
+        pub struct Name;
+    }
 }
 
-use baz::Name;
+use baz::foo;
 
-pub fn foo() {
+pub fn qux() {
     use bar::*;
-    Name;
+    use foo::Name; // `foo` is ambiguous
 }
 ```
 
-* I'd like to have a better understanding of why this doesn't trigger ambiguity errors.
-    * I'm taking a guess but I think it has to do with how and when we resolve
-      names during early resolution. We resolve all the imports but ambiguities
-      only occur when observed, so we'd need to try to resolve Name during
-      early resolution which simply won't happen because it is a struct so it
-      will never be visited for resolution during expansion.
-    * We will end up resolving the imports themselves, but they'll resolve fine
-      because the imports themselves aren't ambiguous
-    * By the time we get to late resolution we no longer expect there to be any
-      ambiguities, so we will happily return the first resolution result and
-      never search for additional ambiguities, so we resolve directly to
-      `bar::Name` through the glob import
-
-    * doing it with macros produced the expected error
 ```rust
 mod bar {
     macro_rules! name {
@@ -253,33 +302,34 @@ pub fn foo() {
 }
 ```
 
-* how does it work with imports? The same as macros, same error during early resolution
-
-```rust
-mod bar {
-    pub mod foo {
-        pub struct Name;
-    }
-}
-
-mod baz {
-    pub mod foo {
-        pub struct Name;
-    }
-}
-
-use baz::foo;
-
-pub fn foo() {
-    use bar::*;
-    use foo::Name; // `foo` is ambiguous
-}
-```
+> **NOTE** These ambiguity errors are specific to imports, even though they are
+> only observed when those imports are used, having multiple candidates
+> available for a given name during later stages of resolution is not
+> considered an error, so long as none of the imports themselves are ambiguous,
+> there will always be a single unambiguous closest resolution during later
+> stages.
+>
+> ```rust
+> mod bar {
+>     pub struct Name;
+> }
+>
+> mod baz {
+>     pub struct Name;
+> }
+>
+> use baz::Name;
+>
+> pub fn foo() {
+>     use bar::*;
+>     Name; // resolves to bar::Name
+> }
+> ```
 
 r[names.resolution.early.imports.errors.ambiguity.globvsexpanded]
 * Grey Area
 
-r[names.resolution.early.macros]
+r[names.resolution.expansion.macros]
 
 * .visitation-order
     * derive helpers
@@ -301,7 +351,7 @@ r[names.resolution.early.macros]
     * macros are split into two subnamespaces, one for bang macros, and the other for attributes and derives. Resolution candidates from the incorrect subnamespace are ignored
         * https://doc.rust-lang.org/nightly/reference/names/namespaces.html#r-names.namespaces.sub-namespaces
 
-r[names.resolution.early.macros.errors.reserved-names]
+r[names.resolution.expansion.macros.errors.reserved-names]
 
 the names cfg and cfg_attr are reserved in the macro attribute sub-namespace