Merge #4234

4234: Support local_inner_macros r=jonas-schievink a=edwin0cheng

This PR implements `#[macro_export(local_inner_macros)]` support. 

Note that the rustc implementation is quite [hacky][1] too. :)

[1]: 614f273e93/src/librustc_resolve/macros.rs (L456)

Co-authored-by: Edwin Cheng <edwin0cheng@gmail.com>

crates/ra_hir_expand/src/builtin_derive.rs

@@ -38,7 +38,7 @@ macro_rules! register_builtin {
                  _ => return None,
             };
 
-            Some(MacroDefId { krate: None, ast_id: None, kind: MacroDefKind::BuiltInDerive(kind) })
+            Some(MacroDefId { krate: None, ast_id: None, kind: MacroDefKind::BuiltInDerive(kind), local_inner: false })
         }
     };
 }

crates/ra_hir_expand/src/builtin_macro.rs

@@ -73,11 +73,13 @@ pub fn find_builtin_macro(
             krate: Some(krate),
             ast_id: Some(ast_id),
             kind: MacroDefKind::BuiltIn(kind),
+            local_inner: false,
         }),
         Either::Right(kind) => Some(MacroDefId {
             krate: Some(krate),
             ast_id: Some(ast_id),
             kind: MacroDefKind::BuiltInEager(kind),
+            local_inner: false,
         }),
     }
 }
@@ -406,6 +408,7 @@ mod tests {
                     krate: Some(CrateId(0)),
                     ast_id: Some(AstId::new(file_id.into(), ast_id_map.ast_id(&macro_calls[0]))),
                     kind: MacroDefKind::BuiltIn(expander),
+                    local_inner: false,
                 };
 
                 let loc = MacroCallLoc {
@@ -425,6 +428,7 @@ mod tests {
                     krate: Some(CrateId(0)),
                     ast_id: Some(AstId::new(file_id.into(), ast_id_map.ast_id(&macro_calls[0]))),
                     kind: MacroDefKind::BuiltInEager(expander),
+                    local_inner: false,
                 };
 
                 let args = macro_calls[1].token_tree().unwrap();

crates/ra_hir_expand/src/hygiene.rs

@@ -16,31 +16,34 @@ use crate::{
 pub struct Hygiene {
     // This is what `$crate` expands to
     def_crate: Option<CrateId>,
+
+    // Indiciate this is a local inner macro
+    local_inner: bool,
 }
 
 impl Hygiene {
     pub fn new(db: &dyn AstDatabase, file_id: HirFileId) -> Hygiene {
-        let def_crate = match file_id.0 {
-            HirFileIdRepr::FileId(_) => None,
+        let (def_crate, local_inner) = match file_id.0 {
+            HirFileIdRepr::FileId(_) => (None, false),
             HirFileIdRepr::MacroFile(macro_file) => match macro_file.macro_call_id {
                 MacroCallId::LazyMacro(id) => {
                     let loc = db.lookup_intern_macro(id);
                     match loc.def.kind {
-                        MacroDefKind::Declarative => loc.def.krate,
-                        MacroDefKind::BuiltIn(_) => None,
-                        MacroDefKind::BuiltInDerive(_) => None,
-                        MacroDefKind::BuiltInEager(_) => None,
-                        MacroDefKind::CustomDerive(_) => None,
+                        MacroDefKind::Declarative => (loc.def.krate, loc.def.local_inner),
+                        MacroDefKind::BuiltIn(_) => (None, false),
+                        MacroDefKind::BuiltInDerive(_) => (None, false),
+                        MacroDefKind::BuiltInEager(_) => (None, false),
+                        MacroDefKind::CustomDerive(_) => (None, false),
                     }
                 }
-                MacroCallId::EagerMacro(_id) => None,
+                MacroCallId::EagerMacro(_id) => (None, false),
             },
         };
-        Hygiene { def_crate }
+        Hygiene { def_crate, local_inner }
     }
 
     pub fn new_unhygienic() -> Hygiene {
-        Hygiene { def_crate: None }
+        Hygiene { def_crate: None, local_inner: false }
     }
 
     // FIXME: this should just return name
@@ -52,4 +55,12 @@ impl Hygiene {
         }
         Either::Left(name_ref.as_name())
     }
+
+    pub fn local_inner_macros(&self) -> Option<CrateId> {
+        if self.local_inner {
+            self.def_crate
+        } else {
+            None
+        }
+    }
 }

crates/ra_hir_expand/src/lib.rs

@@ -204,6 +204,8 @@ pub struct MacroDefId {
     pub krate: Option<CrateId>,
     pub ast_id: Option<AstId<ast::MacroCall>>,
     pub kind: MacroDefKind,
+
+    pub local_inner: bool,
 }
 
 impl MacroDefId {