Merge #1795

1795: Make macro scope a real name scope and fix some details r=matklad a=uHOOCCOOHu

This PR make macro's module scope a real name scope in `PerNs`, instead of handling `Either<PerNs, MacroDef>` everywhere.

In `rustc`, the macro scope behave exactly the same as type and value scope.
It is valid that macros, types and values having exact the same name, and a `use` statement will import all of them. This happened to module `alloc::vec` and macro `alloc::vec!`.
So `Either` is not suitable here.

There is a trap that not only does `#[macro_use]` import all `#[macro_export] macro_rules`, but also imports all macros `use`d in the crate root.
In other words, it just _imports all macros in the module scope of crate root_. (Visibility of `use` doesn't matter.)

And it also happened to `libstd` which has `use alloc_crate::vec;` in crate root to re-export `alloc::vec`, which it both a module and a macro.
The current implementation of `#[macro_use] extern crate` doesn't work here, so that is why only macros directly from  `libstd` like `dbg!` work, while `vec!` from `liballoc` doesn't.
This PR fixes this.

Another point is that, after some tests, I figure out that _`macro_rules` does NOT define macro in current module scope at all_.
It defines itself in legacy textual scope. And if `#[macro_export]` is given, it also is defined ONLY in module scope of crate root. (Then being `macro_use`d, as mentioned above)
(Well, the nightly [Declarative Macro 2.0](https://github.com/rust-lang/rust/issues/39412) simply always define in current module scope only, just like normal items do. But it is not yet supported by us)

After this PR, in my test, all non-builtin macros are resolved now. (Hover text for documentation is available) So it fixes #1688 . Since compiler builtin macros are marked as `#[rustc_doc_only_macro]` instead of `#[macro_export]`, we can simply tweak the condition to let it resolved, but it may cause expansion error.

Some critical notes are also given in doc-comments.

<img width="447" alt="Screenshot_20190909_223859" src="https://user-images.githubusercontent.com/14816024/64540366-ac1ef600-d352-11e9-804f-566ba7559206.png">


Co-authored-by: uHOOCCOOHu <[email protected]>

1 files changed, 24 insertions, 22 deletions

diff --git a/crates/ra_hir/src/nameres/tests.rs b/crates/ra_hir/src/nameres/tests.rs
index 4ff897ca5..bc4b47b70 100644
--- a/crates/ra_hir/src/nameres/tests.rs
+++ b/crates/ra_hir/src/nameres/tests.rs
@@ -12,8 +12,7 @@ use test_utils::covers;
 
 use crate::{
     mock::{CrateGraphFixture, MockDatabase},
-    nameres::Resolution,
-    Crate, Either,
+    Crate,
 };
 
 use super::*;
@@ -37,35 +36,38 @@ fn render_crate_def_map(map: &CrateDefMap) -> String {
         *buf += path;
         *buf += "\n";
 
-        let items = map.modules[module].scope.items.iter().map(|(name, it)| (name, Either::A(it)));
-        let macros = map.modules[module].scope.macros.iter().map(|(name, m)| (name, Either::B(m)));
-        let mut entries = items.chain(macros).collect::<Vec<_>>();
-
+        let mut entries = map.modules[module]
+            .scope
+            .items
+            .iter()
+            .map(|(name, res)| (name, res.def))
+            .collect::<Vec<_>>();
         entries.sort_by_key(|(name, _)| *name);
+
         for (name, res) in entries {
-            match res {
-                Either::A(it) => {
-                    *buf += &format!("{}: {}\n", name, dump_resolution(it));
-                }
-                Either::B(_) => {
-                    *buf += &format!("{}: m\n", name);
-                }
+            *buf += &format!("{}:", name);
+
+            if res.types.is_some() {
+                *buf += " t";
+            }
+            if res.values.is_some() {
+                *buf += " v";
+            }
+            if res.macros.is_some() {
+                *buf += " m";
+            }
+            if res.is_none() {
+                *buf += " _";
             }
+
+            *buf += "\n";
         }
+
         for (name, child) in map.modules[module].children.iter() {
             let path = path.to_string() + &format!("::{}", name);
             go(buf, map, &path, *child);
         }
     }
-
-    fn dump_resolution(resolution: &Resolution) -> &'static str {
-        match (resolution.def.types.is_some(), resolution.def.values.is_some()) {
-            (true, true) => "t v",
-            (true, false) => "t",
-            (false, true) => "v",
-            (false, false) => "_",
-        }
-    }
 }
 
 fn def_map(fixtute: &str) -> String {