Merge #1784

1784: Support textual scoped macros r=matklad a=uHOOCCOOHu

Refactor the old simulation with `global_macro_scope`.

Now it is quite accurate to resolve textual scoped macros.
- Expand textual scoped macros in item and non-item place.
- Support `#[macro_use]` on `mod`.
- Textual scoped macros are collected into `nameres::ModuleScope`, so I think it makes #1727 easier to fix.
- It is implemented in a simple way to `clone()` current scoped macro ids into sub-modules. Though only indices are cloned, it will still increase some resolving time. Well, I've not bench-marked yet.

In my test with vscode extension, it can now successfully expand `dbg!` from `std` without `std::` prefix. "Goto definition" also works. Screenshot here:
<img width="281" alt="Screenshot_20190907_043442" src="https://user-images.githubusercontent.com/14816024/64458794-ddb47900-d128-11e9-95e3-1c8569978825.png">


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

1 files changed, 35 insertions, 0 deletions

diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index c4bddde85..25716fe8c 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -2803,6 +2803,41 @@ fn main() {
     );
 }
 
+#[test]
+fn infer_legacy_textual_scoped_macros_expanded() {
+    assert_snapshot!(
+        infer(r#"
+struct Foo(Vec<i32>);
+
+#[macro_use]
+mod m {
+    macro_rules! foo {
+        ($($item:expr),*) => {
+            {
+                Foo(vec![$($item,)*])
+            }
+        };
+    }
+}
+
+fn main() {
+    let x = foo!(1,2);
+    let y = crate::foo!(1,2);
+}
+"#),
+        @r###"
+    ![0; 17) '{Foo(v...,2,])}': Foo
+    ![1; 4) 'Foo': Foo({unknown}) -> Foo
+    ![1; 16) 'Foo(vec![1,2,])': Foo
+    ![5; 15) 'vec![1,2,]': {unknown}
+    [195; 251) '{     ...,2); }': ()
+    [205; 206) 'x': Foo
+    [228; 229) 'y': {unknown}
+    [232; 248) 'crate:...!(1,2)': {unknown}
+    "###
+    );
+}
+
 #[ignore]
 #[test]
 fn method_resolution_trait_before_autoref() {