10 files changed, 117 insertions, 40 deletions

diff --git a/crates/ra_hir_def/src/adt.rs b/crates/ra_hir_def/src/adt.rs
index 7c0d93691..753becc3d 100644
--- a/crates/ra_hir_def/src/adt.rs
+++ b/crates/ra_hir_def/src/adt.rs
@@ -14,7 +14,7 @@ use ra_syntax::ast::{self, NameOwner, TypeAscriptionOwner, VisibilityOwner};
 use crate::{
     body::CfgExpander, db::DefDatabase, src::HasChildSource, src::HasSource, trace::Trace,
     type_ref::TypeRef, visibility::RawVisibility, EnumId, HasModule, LocalEnumVariantId,
-    LocalStructFieldId, Lookup, ModuleId, StructId, UnionId, VariantId,
+    LocalFieldId, Lookup, ModuleId, StructId, UnionId, VariantId,
 };
 
 /// Note that we use `StructData` for unions as well!
@@ -38,14 +38,14 @@ pub struct EnumVariantData {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum VariantData {
-    Record(Arena<StructFieldData>),
-    Tuple(Arena<StructFieldData>),
+    Record(Arena<FieldData>),
+    Tuple(Arena<FieldData>),
     Unit,
 }
 
 /// A single field of an enum variant or struct
 #[derive(Debug, Clone, PartialEq, Eq)]
-pub struct StructFieldData {
+pub struct FieldData {
     pub name: Name,
     pub type_ref: TypeRef,
     pub visibility: RawVisibility,
@@ -133,15 +133,15 @@ impl VariantData {
         }
     }
 
-    pub fn fields(&self) -> &Arena<StructFieldData> {
-        const EMPTY: &Arena<StructFieldData> = &Arena::new();
+    pub fn fields(&self) -> &Arena<FieldData> {
+        const EMPTY: &Arena<FieldData> = &Arena::new();
         match &self {
             VariantData::Record(fields) | VariantData::Tuple(fields) => fields,
             _ => EMPTY,
         }
     }
 
-    pub fn field(&self, name: &Name) -> Option<LocalStructFieldId> {
+    pub fn field(&self, name: &Name) -> Option<LocalFieldId> {
         self.fields().iter().find_map(|(id, data)| if &data.name == name { Some(id) } else { None })
     }
 
@@ -155,7 +155,7 @@ impl VariantData {
 }
 
 impl HasChildSource for VariantId {
-    type ChildId = LocalStructFieldId;
+    type ChildId = LocalFieldId;
     type Value = Either<ast::TupleFieldDef, ast::RecordFieldDef>;
 
     fn child_source(&self, db: &dyn DefDatabase) -> InFile<ArenaMap<Self::ChildId, Self::Value>> {
@@ -195,7 +195,7 @@ pub enum StructKind {
 fn lower_struct(
     db: &dyn DefDatabase,
     expander: &mut CfgExpander,
-    trace: &mut Trace<StructFieldData, Either<ast::TupleFieldDef, ast::RecordFieldDef>>,
+    trace: &mut Trace<FieldData, Either<ast::TupleFieldDef, ast::RecordFieldDef>>,
     ast: &InFile<ast::StructKind>,
 ) -> StructKind {
     match &ast.value {
@@ -208,7 +208,7 @@ fn lower_struct(
 
                 trace.alloc(
                     || Either::Left(fd.clone()),
-                    || StructFieldData {
+                    || FieldData {
                         name: Name::new_tuple_field(i),
                         type_ref: TypeRef::from_ast_opt(fd.type_ref()),
                         visibility: RawVisibility::from_ast(db, ast.with_value(fd.visibility())),
@@ -226,7 +226,7 @@ fn lower_struct(
 
                 trace.alloc(
                     || Either::Right(fd.clone()),
-                    || StructFieldData {
+                    || FieldData {
                         name: fd.name().map(|n| n.as_name()).unwrap_or_else(Name::missing),
                         type_ref: TypeRef::from_ast_opt(fd.ascribed_type()),
                         visibility: RawVisibility::from_ast(db, ast.with_value(fd.visibility())),
diff --git a/crates/ra_hir_def/src/attr.rs b/crates/ra_hir_def/src/attr.rs
index 2f2e3e5ba..5a86af8ba 100644
--- a/crates/ra_hir_def/src/attr.rs
+++ b/crates/ra_hir_def/src/attr.rs
@@ -13,7 +13,8 @@ use ra_syntax::{
 use tt::Subtree;
 
 use crate::{
-    db::DefDatabase, path::ModPath, src::HasChildSource, src::HasSource, AdtId, AttrDefId, Lookup,
+    db::DefDatabase, nameres::ModuleSource, path::ModPath, src::HasChildSource, src::HasSource,
+    AdtId, AttrDefId, Lookup,
 };
 
 #[derive(Default, Debug, Clone, PartialEq, Eq)]
@@ -37,13 +38,21 @@ impl Attrs {
         match def {
             AttrDefId::ModuleId(module) => {
                 let def_map = db.crate_def_map(module.krate);
-                let src = match def_map[module.local_id].declaration_source(db) {
-                    Some(it) => it,
-                    None => return Attrs::default(),
-                };
-                Attrs::from_attrs_owner(db, src.as_ref().map(|it| it as &dyn AttrsOwner))
+                let mod_data = &def_map[module.local_id];
+                match mod_data.declaration_source(db) {
+                    Some(it) => {
+                        Attrs::from_attrs_owner(db, it.as_ref().map(|it| it as &dyn AttrsOwner))
+                    }
+                    None => Attrs::from_attrs_owner(
+                        db,
+                        mod_data.definition_source(db).as_ref().map(|src| match src {
+                            ModuleSource::SourceFile(file) => file as &dyn AttrsOwner,
+                            ModuleSource::Module(module) => module as &dyn AttrsOwner,
+                        }),
+                    ),
+                }
             }
-            AttrDefId::StructFieldId(it) => {
+            AttrDefId::FieldId(it) => {
                 let src = it.parent.child_source(db);
                 match &src.value[it.local_id] {
                     Either::Left(_tuple) => Attrs::default(),
@@ -106,7 +115,9 @@ pub struct Attr {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum AttrInput {
+    /// `#[attr = "string"]`
     Literal(SmolStr),
+    /// `#[attr(subtree)]`
     TokenTree(Subtree),
 }
 
diff --git a/crates/ra_hir_def/src/body.rs b/crates/ra_hir_def/src/body.rs
index 3b169440a..890cefcaf 100644
--- a/crates/ra_hir_def/src/body.rs
+++ b/crates/ra_hir_def/src/body.rs
@@ -27,7 +27,7 @@ use crate::{
     AsMacroCall, DefWithBodyId, HasModule, Lookup, ModuleId,
 };
 
-/// A subser of Exander that only deals with cfg attributes. We only need it to
+/// A subset of Exander that only deals with cfg attributes. We only need it to
 /// avoid cyclic queries in crate def map during enum processing.
 pub(crate) struct CfgExpander {
     cfg_options: CfgOptions,
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index 0caedd8d8..571603854 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -141,6 +141,10 @@ impl ExprCollector<'_> {
 
     fn collect_expr(&mut self, expr: ast::Expr) -> ExprId {
         let syntax_ptr = AstPtr::new(&expr);
+        let attrs = self.expander.parse_attrs(&expr);
+        if !self.expander.is_cfg_enabled(&attrs) {
+            return self.missing_expr();
+        }
         match expr {
             ast::Expr::IfExpr(e) => {
                 let then_branch = self.collect_block_opt(e.then_branch());
diff --git a/crates/ra_hir_def/src/body/scope.rs b/crates/ra_hir_def/src/body/scope.rs
index 5b36a7cc1..86f953c80 100644
--- a/crates/ra_hir_def/src/body/scope.rs
+++ b/crates/ra_hir_def/src/body/scope.rs
@@ -194,7 +194,7 @@ mod tests {
         let (off, code) = extract_offset(code);
         let code = {
             let mut buf = String::new();
-            let off = off.to_usize();
+            let off: usize = off.into();
             buf.push_str(&code[..off]);
             buf.push_str("marker");
             buf.push_str(&code[off..]);
diff --git a/crates/ra_hir_def/src/child_by_source.rs b/crates/ra_hir_def/src/child_by_source.rs
index 7009f21d1..a885ec96d 100644
--- a/crates/ra_hir_def/src/child_by_source.rs
+++ b/crates/ra_hir_def/src/child_by_source.rs
@@ -12,8 +12,8 @@ use crate::{
     item_scope::ItemScope,
     keys,
     src::{HasChildSource, HasSource},
-    AdtId, AssocItemId, DefWithBodyId, EnumId, EnumVariantId, ImplId, Lookup, ModuleDefId,
-    ModuleId, StructFieldId, TraitId, VariantId,
+    AdtId, AssocItemId, DefWithBodyId, EnumId, EnumVariantId, FieldId, ImplId, Lookup, ModuleDefId,
+    ModuleId, TraitId, VariantId,
 };
 
 pub trait ChildBySource {
@@ -140,7 +140,7 @@ impl ChildBySource for VariantId {
         let arena_map = self.child_source(db);
         let arena_map = arena_map.as_ref();
         for (local_id, source) in arena_map.value.iter() {
-            let id = StructFieldId { parent: *self, local_id };
+            let id = FieldId { parent: *self, local_id };
             match source {
                 Either::Left(source) => {
                     res[keys::TUPLE_FIELD].insert(arena_map.with_value(source.clone()), id)
diff --git a/crates/ra_hir_def/src/docs.rs b/crates/ra_hir_def/src/docs.rs
index 0539a77d4..b221ae1ce 100644
--- a/crates/ra_hir_def/src/docs.rs
+++ b/crates/ra_hir_def/src/docs.rs
@@ -43,7 +43,7 @@ impl Documentation {
                 let src = def_map[module.local_id].declaration_source(db)?;
                 docs_from_ast(&src.value)
             }
-            AttrDefId::StructFieldId(it) => {
+            AttrDefId::FieldId(it) => {
                 let src = it.parent.child_source(db);
                 match &src.value[it.local_id] {
                     Either::Left(_tuple) => None,
diff --git a/crates/ra_hir_def/src/find_path.rs b/crates/ra_hir_def/src/find_path.rs
index 81eff5bfe..70dcb03e6 100644
--- a/crates/ra_hir_def/src/find_path.rs
+++ b/crates/ra_hir_def/src/find_path.rs
@@ -19,7 +19,7 @@ impl ModPath {
 
     // When std library is present, paths starting with `std::`
     // should be preferred over paths starting with `core::` and `alloc::`
-    fn should_start_with_std(&self) -> bool {
+    fn can_start_with_std(&self) -> bool {
         self.segments
             .first()
             .filter(|&first_segment| {
@@ -132,6 +132,9 @@ fn find_path_inner(
     }
 
     // - otherwise, look for modules containing (reexporting) it and import it from one of those
+    let crate_root = ModuleId { local_id: def_map.root, krate: from.krate };
+    let crate_attrs = db.attrs(crate_root.into());
+    let prefer_no_std = crate_attrs.by_key("no_std").exists();
     let importable_locations = find_importable_locations(db, item, from);
     let mut best_path = None;
     let mut best_path_len = max_len;
@@ -147,21 +150,32 @@ fn find_path_inner(
         };
         path.segments.push(name);
 
-        let new_path =
-            if let Some(best_path) = best_path { select_best_path(best_path, path) } else { path };
+        let new_path = if let Some(best_path) = best_path {
+            select_best_path(best_path, path, prefer_no_std)
+        } else {
+            path
+        };
         best_path_len = new_path.len();
         best_path = Some(new_path);
     }
     best_path
 }
 
-fn select_best_path(old_path: ModPath, new_path: ModPath) -> ModPath {
-    if old_path.starts_with_std() && new_path.should_start_with_std() {
+fn select_best_path(old_path: ModPath, new_path: ModPath, prefer_no_std: bool) -> ModPath {
+    if old_path.starts_with_std() && new_path.can_start_with_std() {
         tested_by!(prefer_std_paths);
-        old_path
-    } else if new_path.starts_with_std() && old_path.should_start_with_std() {
+        if prefer_no_std {
+            new_path
+        } else {
+            old_path
+        }
+    } else if new_path.starts_with_std() && old_path.can_start_with_std() {
         tested_by!(prefer_std_paths);
-        new_path
+        if prefer_no_std {
+            old_path
+        } else {
+            new_path
+        }
     } else if new_path.len() < old_path.len() {
         new_path
     } else {
@@ -513,6 +527,54 @@ mod tests {
     }
 
     #[test]
+    fn prefer_alloc_paths_over_std() {
+        covers!(prefer_std_paths);
+        let code = r#"
+        //- /main.rs crate:main deps:alloc,std
+        #![no_std]
+
+        <|>
+
+        //- /std.rs crate:std deps:alloc
+
+        pub mod sync {
+            pub use alloc::sync::Arc;
+        }
+
+        //- /zzz.rs crate:alloc
+
+        pub mod sync {
+            pub struct Arc;
+        }
+        "#;
+        check_found_path(code, "alloc::sync::Arc");
+    }
+
+    #[test]
+    fn prefer_core_paths_over_std() {
+        covers!(prefer_std_paths);
+        let code = r#"
+        //- /main.rs crate:main deps:core,std
+        #![no_std]
+
+        <|>
+
+        //- /std.rs crate:std deps:core
+
+        pub mod fmt {
+            pub use core::fmt::Error;
+        }
+
+        //- /zzz.rs crate:core
+
+        pub mod fmt {
+            pub struct Error;
+        }
+        "#;
+        check_found_path(code, "core::fmt::Error");
+    }
+
+    #[test]
     fn prefer_shorter_paths_if_not_alloc() {
         let code = r#"
         //- /main.rs crate:main deps:megaalloc,std
diff --git a/crates/ra_hir_def/src/keys.rs b/crates/ra_hir_def/src/keys.rs
index 8cd70eb9a..a7349a21d 100644
--- a/crates/ra_hir_def/src/keys.rs
+++ b/crates/ra_hir_def/src/keys.rs
@@ -8,7 +8,7 @@ use rustc_hash::FxHashMap;
 
 use crate::{
     dyn_map::{DynMap, Policy},
-    ConstId, EnumId, EnumVariantId, FunctionId, ImplId, StaticId, StructFieldId, StructId, TraitId,
+    ConstId, EnumId, EnumVariantId, FieldId, FunctionId, ImplId, StaticId, StructId, TraitId,
     TypeAliasId, TypeParamId, UnionId,
 };
 
@@ -25,8 +25,8 @@ pub const UNION: Key<ast::UnionDef, UnionId> = Key::new();
 pub const ENUM: Key<ast::EnumDef, EnumId> = Key::new();
 
 pub const ENUM_VARIANT: Key<ast::EnumVariant, EnumVariantId> = Key::new();
-pub const TUPLE_FIELD: Key<ast::TupleFieldDef, StructFieldId> = Key::new();
-pub const RECORD_FIELD: Key<ast::RecordFieldDef, StructFieldId> = Key::new();
+pub const TUPLE_FIELD: Key<ast::TupleFieldDef, FieldId> = Key::new();
+pub const RECORD_FIELD: Key<ast::RecordFieldDef, FieldId> = Key::new();
 pub const TYPE_PARAM: Key<ast::TypeParam, TypeParamId> = Key::new();
 
 pub const MACRO: Key<ast::MacroCall, MacroDefId> = Key::new();
diff --git a/crates/ra_hir_def/src/lib.rs b/crates/ra_hir_def/src/lib.rs
index 2d27bbdf8..518772e8a 100644
--- a/crates/ra_hir_def/src/lib.rs
+++ b/crates/ra_hir_def/src/lib.rs
@@ -133,12 +133,12 @@ pub struct EnumVariantId {
 pub type LocalEnumVariantId = Idx<adt::EnumVariantData>;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct StructFieldId {
+pub struct FieldId {
     pub parent: VariantId,
-    pub local_id: LocalStructFieldId,
+    pub local_id: LocalFieldId,
 }
 
-pub type LocalStructFieldId = Idx<adt::StructFieldData>;
+pub type LocalFieldId = Idx<adt::FieldData>;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ConstId(salsa::InternId);
@@ -299,7 +299,7 @@ impl From<AssocItemId> for GenericDefId {
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum AttrDefId {
     ModuleId(ModuleId),
-    StructFieldId(StructFieldId),
+    FieldId(FieldId),
     AdtId(AdtId),
     FunctionId(FunctionId),
     EnumVariantId(EnumVariantId),
@@ -313,7 +313,7 @@ pub enum AttrDefId {
 
 impl_froms!(
     AttrDefId: ModuleId,
-    StructFieldId,
+    FieldId,
     AdtId(StructId, EnumId, UnionId),
     EnumVariantId,
     StaticId,