1 files changed, 850 insertions, 0 deletions

diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
new file mode 100644
index 000000000..d8beac98a
--- /dev/null
+++ b/crates/hir/src/semantics.rs
@@ -0,0 +1,850 @@
+//! See `Semantics`.
+
+mod source_to_def;
+
+use std::{cell::RefCell, fmt, iter::successors};
+
+use base_db::{FileId, FileRange};
+use hir_def::{
+    resolver::{self, HasResolver, Resolver},
+    AsMacroCall, FunctionId, TraitId, VariantId,
+};
+use hir_expand::{hygiene::Hygiene, name::AsName, ExpansionInfo};
+use hir_ty::associated_type_shorthand_candidates;
+use itertools::Itertools;
+use rustc_hash::{FxHashMap, FxHashSet};
+use syntax::{
+    algo::{find_node_at_offset, skip_trivia_token},
+    ast, AstNode, Direction, SyntaxNode, SyntaxToken, TextRange, TextSize,
+};
+
+use crate::{
+    db::HirDatabase,
+    diagnostics::Diagnostic,
+    semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
+    source_analyzer::{resolve_hir_path, resolve_hir_path_qualifier, SourceAnalyzer},
+    AssocItem, Callable, Crate, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef,
+    Module, ModuleDef, Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, TypeRef,
+    VariantDef,
+};
+use resolver::TypeNs;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum PathResolution {
+    /// An item
+    Def(ModuleDef),
+    /// A local binding (only value namespace)
+    Local(Local),
+    /// A generic parameter
+    TypeParam(TypeParam),
+    SelfType(ImplDef),
+    Macro(MacroDef),
+    AssocItem(AssocItem),
+}
+
+impl PathResolution {
+    fn in_type_ns(&self) -> Option<TypeNs> {
+        match self {
+            PathResolution::Def(ModuleDef::Adt(adt)) => Some(TypeNs::AdtId((*adt).into())),
+            PathResolution::Def(ModuleDef::BuiltinType(builtin)) => {
+                Some(TypeNs::BuiltinType(*builtin))
+            }
+            PathResolution::Def(ModuleDef::Const(_))
+            | PathResolution::Def(ModuleDef::EnumVariant(_))
+            | PathResolution::Def(ModuleDef::Function(_))
+            | PathResolution::Def(ModuleDef::Module(_))
+            | PathResolution::Def(ModuleDef::Static(_))
+            | PathResolution::Def(ModuleDef::Trait(_)) => None,
+            PathResolution::Def(ModuleDef::TypeAlias(alias)) => {
+                Some(TypeNs::TypeAliasId((*alias).into()))
+            }
+            PathResolution::Local(_) | PathResolution::Macro(_) => None,
+            PathResolution::TypeParam(param) => Some(TypeNs::GenericParam((*param).into())),
+            PathResolution::SelfType(impl_def) => Some(TypeNs::SelfType((*impl_def).into())),
+            PathResolution::AssocItem(AssocItem::Const(_))
+            | PathResolution::AssocItem(AssocItem::Function(_)) => None,
+            PathResolution::AssocItem(AssocItem::TypeAlias(alias)) => {
+                Some(TypeNs::TypeAliasId((*alias).into()))
+            }
+        }
+    }
+
+    /// Returns an iterator over associated types that may be specified after this path (using
+    /// `Ty::Assoc` syntax).
+    pub fn assoc_type_shorthand_candidates<R>(
+        &self,
+        db: &dyn HirDatabase,
+        mut cb: impl FnMut(TypeAlias) -> Option<R>,
+    ) -> Option<R> {
+        associated_type_shorthand_candidates(db, self.in_type_ns()?, |_, _, id| cb(id.into()))
+    }
+}
+
+/// Primary API to get semantic information, like types, from syntax trees.
+pub struct Semantics<'db, DB> {
+    pub db: &'db DB,
+    imp: SemanticsImpl<'db>,
+}
+
+pub struct SemanticsImpl<'db> {
+    pub db: &'db dyn HirDatabase,
+    s2d_cache: RefCell<SourceToDefCache>,
+    expansion_info_cache: RefCell<FxHashMap<HirFileId, Option<ExpansionInfo>>>,
+    cache: RefCell<FxHashMap<SyntaxNode, HirFileId>>,
+}
+
+impl<DB> fmt::Debug for Semantics<'_, DB> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Semantics {{ ... }}")
+    }
+}
+
+impl<'db, DB: HirDatabase> Semantics<'db, DB> {
+    pub fn new(db: &DB) -> Semantics<DB> {
+        let impl_ = SemanticsImpl::new(db);
+        Semantics { db, imp: impl_ }
+    }
+
+    pub fn parse(&self, file_id: FileId) -> ast::SourceFile {
+        self.imp.parse(file_id)
+    }
+
+    pub fn expand(&self, macro_call: &ast::MacroCall) -> Option<SyntaxNode> {
+        self.imp.expand(macro_call)
+    }
+
+    pub fn expand_hypothetical(
+        &self,
+        actual_macro_call: &ast::MacroCall,
+        hypothetical_args: &ast::TokenTree,
+        token_to_map: SyntaxToken,
+    ) -> Option<(SyntaxNode, SyntaxToken)> {
+        self.imp.expand_hypothetical(actual_macro_call, hypothetical_args, token_to_map)
+    }
+
+    pub fn descend_into_macros(&self, token: SyntaxToken) -> SyntaxToken {
+        self.imp.descend_into_macros(token)
+    }
+
+    pub fn descend_node_at_offset<N: ast::AstNode>(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> Option<N> {
+        self.imp.descend_node_at_offset(node, offset).find_map(N::cast)
+    }
+
+    pub fn original_range(&self, node: &SyntaxNode) -> FileRange {
+        self.imp.original_range(node)
+    }
+
+    pub fn diagnostics_display_range(&self, diagnostics: &dyn Diagnostic) -> FileRange {
+        self.imp.diagnostics_display_range(diagnostics)
+    }
+
+    pub fn ancestors_with_macros(&self, node: SyntaxNode) -> impl Iterator<Item = SyntaxNode> + '_ {
+        self.imp.ancestors_with_macros(node)
+    }
+
+    pub fn ancestors_at_offset_with_macros(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> impl Iterator<Item = SyntaxNode> + '_ {
+        self.imp.ancestors_at_offset_with_macros(node, offset)
+    }
+
+    /// Find a AstNode by offset inside SyntaxNode, if it is inside *Macrofile*,
+    /// search up until it is of the target AstNode type
+    pub fn find_node_at_offset_with_macros<N: AstNode>(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> Option<N> {
+        self.imp.ancestors_at_offset_with_macros(node, offset).find_map(N::cast)
+    }
+
+    /// Find a AstNode by offset inside SyntaxNode, if it is inside *MacroCall*,
+    /// descend it and find again
+    pub fn find_node_at_offset_with_descend<N: AstNode>(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> Option<N> {
+        if let Some(it) = find_node_at_offset(&node, offset) {
+            return Some(it);
+        }
+
+        self.imp.descend_node_at_offset(node, offset).find_map(N::cast)
+    }
+
+    pub fn type_of_expr(&self, expr: &ast::Expr) -> Option<Type> {
+        self.imp.type_of_expr(expr)
+    }
+
+    pub fn type_of_pat(&self, pat: &ast::Pat) -> Option<Type> {
+        self.imp.type_of_pat(pat)
+    }
+
+    pub fn type_of_self(&self, param: &ast::SelfParam) -> Option<Type> {
+        self.imp.type_of_self(param)
+    }
+
+    pub fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<Function> {
+        self.imp.resolve_method_call(call).map(Function::from)
+    }
+
+    pub fn resolve_method_call_as_callable(&self, call: &ast::MethodCallExpr) -> Option<Callable> {
+        self.imp.resolve_method_call_as_callable(call)
+    }
+
+    pub fn resolve_field(&self, field: &ast::FieldExpr) -> Option<Field> {
+        self.imp.resolve_field(field)
+    }
+
+    pub fn resolve_record_field(
+        &self,
+        field: &ast::RecordExprField,
+    ) -> Option<(Field, Option<Local>)> {
+        self.imp.resolve_record_field(field)
+    }
+
+    pub fn resolve_record_field_pat(&self, field: &ast::RecordPatField) -> Option<Field> {
+        self.imp.resolve_record_field_pat(field)
+    }
+
+    pub fn resolve_macro_call(&self, macro_call: &ast::MacroCall) -> Option<MacroDef> {
+        self.imp.resolve_macro_call(macro_call)
+    }
+
+    pub fn resolve_path(&self, path: &ast::Path) -> Option<PathResolution> {
+        self.imp.resolve_path(path)
+    }
+
+    pub fn resolve_extern_crate(&self, extern_crate: &ast::ExternCrate) -> Option<Crate> {
+        self.imp.resolve_extern_crate(extern_crate)
+    }
+
+    pub fn resolve_variant(&self, record_lit: ast::RecordExpr) -> Option<VariantDef> {
+        self.imp.resolve_variant(record_lit).map(VariantDef::from)
+    }
+
+    pub fn lower_path(&self, path: &ast::Path) -> Option<Path> {
+        self.imp.lower_path(path)
+    }
+
+    pub fn resolve_bind_pat_to_const(&self, pat: &ast::IdentPat) -> Option<ModuleDef> {
+        self.imp.resolve_bind_pat_to_const(pat)
+    }
+
+    // FIXME: use this instead?
+    // pub fn resolve_name_ref(&self, name_ref: &ast::NameRef) -> Option<???>;
+
+    pub fn record_literal_missing_fields(&self, literal: &ast::RecordExpr) -> Vec<(Field, Type)> {
+        self.imp.record_literal_missing_fields(literal)
+    }
+
+    pub fn record_pattern_missing_fields(&self, pattern: &ast::RecordPat) -> Vec<(Field, Type)> {
+        self.imp.record_pattern_missing_fields(pattern)
+    }
+
+    pub fn to_def<T: ToDef>(&self, src: &T) -> Option<T::Def> {
+        let src = self.imp.find_file(src.syntax().clone()).with_value(src).cloned();
+        T::to_def(&self.imp, src)
+    }
+
+    pub fn to_module_def(&self, file: FileId) -> Option<Module> {
+        self.imp.to_module_def(file)
+    }
+
+    pub fn scope(&self, node: &SyntaxNode) -> SemanticsScope<'db> {
+        self.imp.scope(node)
+    }
+
+    pub fn scope_at_offset(&self, node: &SyntaxNode, offset: TextSize) -> SemanticsScope<'db> {
+        self.imp.scope_at_offset(node, offset)
+    }
+
+    pub fn scope_for_def(&self, def: Trait) -> SemanticsScope<'db> {
+        self.imp.scope_for_def(def)
+    }
+
+    pub fn assert_contains_node(&self, node: &SyntaxNode) {
+        self.imp.assert_contains_node(node)
+    }
+
+    pub fn is_unsafe_method_call(&self, method_call_expr: ast::MethodCallExpr) -> bool {
+        self.imp.is_unsafe_method_call(method_call_expr)
+    }
+
+    pub fn is_unsafe_ref_expr(&self, ref_expr: &ast::RefExpr) -> bool {
+        self.imp.is_unsafe_ref_expr(ref_expr)
+    }
+
+    pub fn is_unsafe_ident_pat(&self, ident_pat: &ast::IdentPat) -> bool {
+        self.imp.is_unsafe_ident_pat(ident_pat)
+    }
+}
+
+impl<'db> SemanticsImpl<'db> {
+    fn new(db: &'db dyn HirDatabase) -> Self {
+        SemanticsImpl {
+            db,
+            s2d_cache: Default::default(),
+            cache: Default::default(),
+            expansion_info_cache: Default::default(),
+        }
+    }
+
+    fn parse(&self, file_id: FileId) -> ast::SourceFile {
+        let tree = self.db.parse(file_id).tree();
+        self.cache(tree.syntax().clone(), file_id.into());
+        tree
+    }
+
+    fn expand(&self, macro_call: &ast::MacroCall) -> Option<SyntaxNode> {
+        let macro_call = self.find_file(macro_call.syntax().clone()).with_value(macro_call);
+        let sa = self.analyze2(macro_call.map(|it| it.syntax()), None);
+        let file_id = sa.expand(self.db, macro_call)?;
+        let node = self.db.parse_or_expand(file_id)?;
+        self.cache(node.clone(), file_id);
+        Some(node)
+    }
+
+    fn expand_hypothetical(
+        &self,
+        actual_macro_call: &ast::MacroCall,
+        hypothetical_args: &ast::TokenTree,
+        token_to_map: SyntaxToken,
+    ) -> Option<(SyntaxNode, SyntaxToken)> {
+        let macro_call =
+            self.find_file(actual_macro_call.syntax().clone()).with_value(actual_macro_call);
+        let sa = self.analyze2(macro_call.map(|it| it.syntax()), None);
+        let krate = sa.resolver.krate()?;
+        let macro_call_id = macro_call.as_call_id(self.db.upcast(), krate, |path| {
+            sa.resolver.resolve_path_as_macro(self.db.upcast(), &path)
+        })?;
+        hir_expand::db::expand_hypothetical(
+            self.db.upcast(),
+            macro_call_id,
+            hypothetical_args,
+            token_to_map,
+        )
+    }
+
+    fn descend_into_macros(&self, token: SyntaxToken) -> SyntaxToken {
+        let _p = profile::span("descend_into_macros");
+        let parent = token.parent();
+        let parent = self.find_file(parent);
+        let sa = self.analyze2(parent.as_ref(), None);
+
+        let token = successors(Some(parent.with_value(token)), |token| {
+            self.db.check_canceled();
+            let macro_call = token.value.ancestors().find_map(ast::MacroCall::cast)?;
+            let tt = macro_call.token_tree()?;
+            if !tt.syntax().text_range().contains_range(token.value.text_range()) {
+                return None;
+            }
+            let file_id = sa.expand(self.db, token.with_value(&macro_call))?;
+            let token = self
+                .expansion_info_cache
+                .borrow_mut()
+                .entry(file_id)
+                .or_insert_with(|| file_id.expansion_info(self.db.upcast()))
+                .as_ref()?
+                .map_token_down(token.as_ref())?;
+
+            self.cache(find_root(&token.value.parent()), token.file_id);
+
+            Some(token)
+        })
+        .last()
+        .unwrap();
+
+        token.value
+    }
+
+    fn descend_node_at_offset(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> impl Iterator<Item = SyntaxNode> + '_ {
+        // Handle macro token cases
+        node.token_at_offset(offset)
+            .map(|token| self.descend_into_macros(token))
+            .map(|it| self.ancestors_with_macros(it.parent()))
+            .flatten()
+    }
+
+    fn original_range(&self, node: &SyntaxNode) -> FileRange {
+        let node = self.find_file(node.clone());
+        original_range(self.db, node.as_ref())
+    }
+
+    fn diagnostics_display_range(&self, diagnostics: &dyn Diagnostic) -> FileRange {
+        let src = diagnostics.display_source();
+        let root = self.db.parse_or_expand(src.file_id).unwrap();
+        let node = src.value.to_node(&root);
+        self.cache(root, src.file_id);
+        original_range(self.db, src.with_value(&node))
+    }
+
+    fn ancestors_with_macros(&self, node: SyntaxNode) -> impl Iterator<Item = SyntaxNode> + '_ {
+        let node = self.find_file(node);
+        node.ancestors_with_macros(self.db.upcast()).map(|it| it.value)
+    }
+
+    fn ancestors_at_offset_with_macros(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> impl Iterator<Item = SyntaxNode> + '_ {
+        node.token_at_offset(offset)
+            .map(|token| self.ancestors_with_macros(token.parent()))
+            .kmerge_by(|node1, node2| node1.text_range().len() < node2.text_range().len())
+    }
+
+    fn type_of_expr(&self, expr: &ast::Expr) -> Option<Type> {
+        self.analyze(expr.syntax()).type_of_expr(self.db, &expr)
+    }
+
+    fn type_of_pat(&self, pat: &ast::Pat) -> Option<Type> {
+        self.analyze(pat.syntax()).type_of_pat(self.db, &pat)
+    }
+
+    fn type_of_self(&self, param: &ast::SelfParam) -> Option<Type> {
+        self.analyze(param.syntax()).type_of_self(self.db, &param)
+    }
+
+    fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<FunctionId> {
+        self.analyze(call.syntax()).resolve_method_call(self.db, call)
+    }
+
+    fn resolve_method_call_as_callable(&self, call: &ast::MethodCallExpr) -> Option<Callable> {
+        // FIXME: this erases Substs
+        let func = self.resolve_method_call(call)?;
+        let ty = self.db.value_ty(func.into());
+        let resolver = self.analyze(call.syntax()).resolver;
+        let ty = Type::new_with_resolver(self.db, &resolver, ty.value)?;
+        let mut res = ty.as_callable(self.db)?;
+        res.is_bound_method = true;
+        Some(res)
+    }
+
+    fn resolve_field(&self, field: &ast::FieldExpr) -> Option<Field> {
+        self.analyze(field.syntax()).resolve_field(self.db, field)
+    }
+
+    fn resolve_record_field(&self, field: &ast::RecordExprField) -> Option<(Field, Option<Local>)> {
+        self.analyze(field.syntax()).resolve_record_field(self.db, field)
+    }
+
+    fn resolve_record_field_pat(&self, field: &ast::RecordPatField) -> Option<Field> {
+        self.analyze(field.syntax()).resolve_record_field_pat(self.db, field)
+    }
+
+    fn resolve_macro_call(&self, macro_call: &ast::MacroCall) -> Option<MacroDef> {
+        let sa = self.analyze(macro_call.syntax());
+        let macro_call = self.find_file(macro_call.syntax().clone()).with_value(macro_call);
+        sa.resolve_macro_call(self.db, macro_call)
+    }
+
+    fn resolve_path(&self, path: &ast::Path) -> Option<PathResolution> {
+        self.analyze(path.syntax()).resolve_path(self.db, path)
+    }
+
+    fn resolve_extern_crate(&self, extern_crate: &ast::ExternCrate) -> Option<Crate> {
+        let krate = self.scope(extern_crate.syntax()).krate()?;
+        krate.dependencies(self.db).into_iter().find_map(|dep| {
+            if dep.name == extern_crate.name_ref()?.as_name() {
+                Some(dep.krate)
+            } else {
+                None
+            }
+        })
+    }
+
+    fn resolve_variant(&self, record_lit: ast::RecordExpr) -> Option<VariantId> {
+        self.analyze(record_lit.syntax()).resolve_variant(self.db, record_lit)
+    }
+
+    fn lower_path(&self, path: &ast::Path) -> Option<Path> {
+        let src = self.find_file(path.syntax().clone());
+        Path::from_src(path.clone(), &Hygiene::new(self.db.upcast(), src.file_id.into()))
+    }
+
+    fn resolve_bind_pat_to_const(&self, pat: &ast::IdentPat) -> Option<ModuleDef> {
+        self.analyze(pat.syntax()).resolve_bind_pat_to_const(self.db, pat)
+    }
+
+    fn record_literal_missing_fields(&self, literal: &ast::RecordExpr) -> Vec<(Field, Type)> {
+        self.analyze(literal.syntax())
+            .record_literal_missing_fields(self.db, literal)
+            .unwrap_or_default()
+    }
+
+    fn record_pattern_missing_fields(&self, pattern: &ast::RecordPat) -> Vec<(Field, Type)> {
+        self.analyze(pattern.syntax())
+            .record_pattern_missing_fields(self.db, pattern)
+            .unwrap_or_default()
+    }
+
+    fn with_ctx<F: FnOnce(&mut SourceToDefCtx) -> T, T>(&self, f: F) -> T {
+        let mut cache = self.s2d_cache.borrow_mut();
+        let mut ctx = SourceToDefCtx { db: self.db, cache: &mut *cache };
+        f(&mut ctx)
+    }
+
+    fn to_module_def(&self, file: FileId) -> Option<Module> {
+        self.with_ctx(|ctx| ctx.file_to_def(file)).map(Module::from)
+    }
+
+    fn scope(&self, node: &SyntaxNode) -> SemanticsScope<'db> {
+        let node = self.find_file(node.clone());
+        let resolver = self.analyze2(node.as_ref(), None).resolver;
+        SemanticsScope { db: self.db, file_id: node.file_id, resolver }
+    }
+
+    fn scope_at_offset(&self, node: &SyntaxNode, offset: TextSize) -> SemanticsScope<'db> {
+        let node = self.find_file(node.clone());
+        let resolver = self.analyze2(node.as_ref(), Some(offset)).resolver;
+        SemanticsScope { db: self.db, file_id: node.file_id, resolver }
+    }
+
+    fn scope_for_def(&self, def: Trait) -> SemanticsScope<'db> {
+        let file_id = self.db.lookup_intern_trait(def.id).id.file_id;
+        let resolver = def.id.resolver(self.db.upcast());
+        SemanticsScope { db: self.db, file_id, resolver }
+    }
+
+    fn analyze(&self, node: &SyntaxNode) -> SourceAnalyzer {
+        let src = self.find_file(node.clone());
+        self.analyze2(src.as_ref(), None)
+    }
+
+    fn analyze2(&self, src: InFile<&SyntaxNode>, offset: Option<TextSize>) -> SourceAnalyzer {
+        let _p = profile::span("Semantics::analyze2");
+
+        let container = match self.with_ctx(|ctx| ctx.find_container(src)) {
+            Some(it) => it,
+            None => return SourceAnalyzer::new_for_resolver(Resolver::default(), src),
+        };
+
+        let resolver = match container {
+            ChildContainer::DefWithBodyId(def) => {
+                return SourceAnalyzer::new_for_body(self.db, def, src, offset)
+            }
+            ChildContainer::TraitId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::ImplId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::ModuleId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::EnumId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::VariantId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::TypeAliasId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::GenericDefId(it) => it.resolver(self.db.upcast()),
+        };
+        SourceAnalyzer::new_for_resolver(resolver, src)
+    }
+
+    fn cache(&self, root_node: SyntaxNode, file_id: HirFileId) {
+        assert!(root_node.parent().is_none());
+        let mut cache = self.cache.borrow_mut();
+        let prev = cache.insert(root_node, file_id);
+        assert!(prev == None || prev == Some(file_id))
+    }
+
+    fn assert_contains_node(&self, node: &SyntaxNode) {
+        self.find_file(node.clone());
+    }
+
+    fn lookup(&self, root_node: &SyntaxNode) -> Option<HirFileId> {
+        let cache = self.cache.borrow();
+        cache.get(root_node).copied()
+    }
+
+    fn find_file(&self, node: SyntaxNode) -> InFile<SyntaxNode> {
+        let root_node = find_root(&node);
+        let file_id = self.lookup(&root_node).unwrap_or_else(|| {
+            panic!(
+                "\n\nFailed to lookup {:?} in this Semantics.\n\
+                 Make sure to use only query nodes, derived from this instance of Semantics.\n\
+                 root node:   {:?}\n\
+                 known nodes: {}\n\n",
+                node,
+                root_node,
+                self.cache
+                    .borrow()
+                    .keys()
+                    .map(|it| format!("{:?}", it))
+                    .collect::<Vec<_>>()
+                    .join(", ")
+            )
+        });
+        InFile::new(file_id, node)
+    }
+
+    pub fn is_unsafe_method_call(&self, method_call_expr: ast::MethodCallExpr) -> bool {
+        method_call_expr
+            .expr()
+            .and_then(|expr| {
+                let field_expr = if let ast::Expr::FieldExpr(field_expr) = expr {
+                    field_expr
+                } else {
+                    return None;
+                };
+                let ty = self.type_of_expr(&field_expr.expr()?)?;
+                if !ty.is_packed(self.db) {
+                    return None;
+                }
+
+                let func = self.resolve_method_call(&method_call_expr).map(Function::from)?;
+                let is_unsafe = func.has_self_param(self.db)
+                    && matches!(func.params(self.db).first(), Some(TypeRef::Reference(..)));
+                Some(is_unsafe)
+            })
+            .unwrap_or(false)
+    }
+
+    pub fn is_unsafe_ref_expr(&self, ref_expr: &ast::RefExpr) -> bool {
+        ref_expr
+            .expr()
+            .and_then(|expr| {
+                let field_expr = match expr {
+                    ast::Expr::FieldExpr(field_expr) => field_expr,
+                    _ => return None,
+                };
+                let expr = field_expr.expr()?;
+                self.type_of_expr(&expr)
+            })
+            // Binding a reference to a packed type is possibly unsafe.
+            .map(|ty| ty.is_packed(self.db))
+            .unwrap_or(false)
+
+        // FIXME This needs layout computation to be correct. It will highlight
+        // more than it should with the current implementation.
+    }
+
+    pub fn is_unsafe_ident_pat(&self, ident_pat: &ast::IdentPat) -> bool {
+        if !ident_pat.ref_token().is_some() {
+            return false;
+        }
+
+        ident_pat
+            .syntax()
+            .parent()
+            .and_then(|parent| {
+                // `IdentPat` can live under `RecordPat` directly under `RecordPatField` or
+                // `RecordPatFieldList`. `RecordPatField` also lives under `RecordPatFieldList`,
+                // so this tries to lookup the `IdentPat` anywhere along that structure to the
+                // `RecordPat` so we can get the containing type.
+                let record_pat = ast::RecordPatField::cast(parent.clone())
+                    .and_then(|record_pat| record_pat.syntax().parent())
+                    .or_else(|| Some(parent.clone()))
+                    .and_then(|parent| {
+                        ast::RecordPatFieldList::cast(parent)?
+                            .syntax()
+                            .parent()
+                            .and_then(ast::RecordPat::cast)
+                    });
+
+                // If this doesn't match a `RecordPat`, fallback to a `LetStmt` to see if
+                // this is initialized from a `FieldExpr`.
+                if let Some(record_pat) = record_pat {
+                    self.type_of_pat(&ast::Pat::RecordPat(record_pat))
+                } else if let Some(let_stmt) = ast::LetStmt::cast(parent) {
+                    let field_expr = match let_stmt.initializer()? {
+                        ast::Expr::FieldExpr(field_expr) => field_expr,
+                        _ => return None,
+                    };
+
+                    self.type_of_expr(&field_expr.expr()?)
+                } else {
+                    None
+                }
+            })
+            // Binding a reference to a packed type is possibly unsafe.
+            .map(|ty| ty.is_packed(self.db))
+            .unwrap_or(false)
+    }
+}
+
+pub trait ToDef: AstNode + Clone {
+    type Def;
+
+    fn to_def(sema: &SemanticsImpl, src: InFile<Self>) -> Option<Self::Def>;
+}
+
+macro_rules! to_def_impls {
+    ($(($def:path, $ast:path, $meth:ident)),* ,) => {$(
+        impl ToDef for $ast {
+            type Def = $def;
+            fn to_def(sema: &SemanticsImpl, src: InFile<Self>) -> Option<Self::Def> {
+                sema.with_ctx(|ctx| ctx.$meth(src)).map(<$def>::from)
+            }
+        }
+    )*}
+}
+
+to_def_impls![
+    (crate::Module, ast::Module, module_to_def),
+    (crate::Struct, ast::Struct, struct_to_def),
+    (crate::Enum, ast::Enum, enum_to_def),
+    (crate::Union, ast::Union, union_to_def),
+    (crate::Trait, ast::Trait, trait_to_def),
+    (crate::ImplDef, ast::Impl, impl_to_def),
+    (crate::TypeAlias, ast::TypeAlias, type_alias_to_def),
+    (crate::Const, ast::Const, const_to_def),
+    (crate::Static, ast::Static, static_to_def),
+    (crate::Function, ast::Fn, fn_to_def),
+    (crate::Field, ast::RecordField, record_field_to_def),
+    (crate::Field, ast::TupleField, tuple_field_to_def),
+    (crate::EnumVariant, ast::Variant, enum_variant_to_def),
+    (crate::TypeParam, ast::TypeParam, type_param_to_def),
+    (crate::MacroDef, ast::MacroCall, macro_call_to_def), // this one is dubious, not all calls are macros
+    (crate::Local, ast::IdentPat, bind_pat_to_def),
+];
+
+fn find_root(node: &SyntaxNode) -> SyntaxNode {
+    node.ancestors().last().unwrap()
+}
+
+#[derive(Debug)]
+pub struct SemanticsScope<'a> {
+    pub db: &'a dyn HirDatabase,
+    file_id: HirFileId,
+    resolver: Resolver,
+}
+
+impl<'a> SemanticsScope<'a> {
+    pub fn module(&self) -> Option<Module> {
+        Some(Module { id: self.resolver.module()? })
+    }
+
+    pub fn krate(&self) -> Option<Crate> {
+        Some(Crate { id: self.resolver.krate()? })
+    }
+
+    /// Note: `FxHashSet<TraitId>` should be treated as an opaque type, passed into `Type
+    // FIXME: rename to visible_traits to not repeat scope?
+    pub fn traits_in_scope(&self) -> FxHashSet<TraitId> {
+        let resolver = &self.resolver;
+        resolver.traits_in_scope(self.db.upcast())
+    }
+
+    pub fn process_all_names(&self, f: &mut dyn FnMut(Name, ScopeDef)) {
+        let resolver = &self.resolver;
+
+        resolver.process_all_names(self.db.upcast(), &mut |name, def| {
+            let def = match def {
+                resolver::ScopeDef::PerNs(it) => {
+                    let items = ScopeDef::all_items(it);
+                    for item in items {
+                        f(name.clone(), item);
+                    }
+                    return;
+                }
+                resolver::ScopeDef::ImplSelfType(it) => ScopeDef::ImplSelfType(it.into()),
+                resolver::ScopeDef::AdtSelfType(it) => ScopeDef::AdtSelfType(it.into()),
+                resolver::ScopeDef::GenericParam(id) => ScopeDef::GenericParam(TypeParam { id }),
+                resolver::ScopeDef::Local(pat_id) => {
+                    let parent = resolver.body_owner().unwrap().into();
+                    ScopeDef::Local(Local { parent, pat_id })
+                }
+            };
+            f(name, def)
+        })
+    }
+
+    /// Resolve a path as-if it was written at the given scope. This is
+    /// necessary a heuristic, as it doesn't take hygiene into account.
+    pub fn resolve_hypothetical(&self, path: &ast::Path) -> Option<PathResolution> {
+        let hygiene = Hygiene::new(self.db.upcast(), self.file_id);
+        let path = Path::from_src(path.clone(), &hygiene)?;
+        self.resolve_hir_path(&path)
+    }
+
+    pub fn resolve_hir_path(&self, path: &Path) -> Option<PathResolution> {
+        resolve_hir_path(self.db, &self.resolver, path)
+    }
+
+    /// Resolves a path where we know it is a qualifier of another path.
+    ///
+    /// For example, if we have:
+    /// ```
+    /// mod my {
+    ///     pub mod foo {
+    ///         struct Bar;
+    ///     }
+    ///
+    ///     pub fn foo() {}
+    /// }
+    /// ```
+    /// then we know that `foo` in `my::foo::Bar` refers to the module, not the function.
+    pub fn resolve_hir_path_qualifier(&self, path: &Path) -> Option<PathResolution> {
+        resolve_hir_path_qualifier(self.db, &self.resolver, path)
+    }
+}
+
+// FIXME: Change `HasSource` trait to work with `Semantics` and remove this?
+pub fn original_range(db: &dyn HirDatabase, node: InFile<&SyntaxNode>) -> FileRange {
+    if let Some(range) = original_range_opt(db, node) {
+        let original_file = range.file_id.original_file(db.upcast());
+        if range.file_id == original_file.into() {
+            return FileRange { file_id: original_file, range: range.value };
+        }
+
+        log::error!("Fail to mapping up more for {:?}", range);
+        return FileRange { file_id: range.file_id.original_file(db.upcast()), range: range.value };
+    }
+
+    // Fall back to whole macro call
+    if let Some(expansion) = node.file_id.expansion_info(db.upcast()) {
+        if let Some(call_node) = expansion.call_node() {
+            return FileRange {
+                file_id: call_node.file_id.original_file(db.upcast()),
+                range: call_node.value.text_range(),
+            };
+        }
+    }
+
+    FileRange { file_id: node.file_id.original_file(db.upcast()), range: node.value.text_range() }
+}
+
+fn original_range_opt(
+    db: &dyn HirDatabase,
+    node: InFile<&SyntaxNode>,
+) -> Option<InFile<TextRange>> {
+    let expansion = node.file_id.expansion_info(db.upcast())?;
+
+    // the input node has only one token ?
+    let single = skip_trivia_token(node.value.first_token()?, Direction::Next)?
+        == skip_trivia_token(node.value.last_token()?, Direction::Prev)?;
+
+    Some(node.value.descendants().find_map(|it| {
+        let first = skip_trivia_token(it.first_token()?, Direction::Next)?;
+        let first = ascend_call_token(db, &expansion, node.with_value(first))?;
+
+        let last = skip_trivia_token(it.last_token()?, Direction::Prev)?;
+        let last = ascend_call_token(db, &expansion, node.with_value(last))?;
+
+        if (!single && first == last) || (first.file_id != last.file_id) {
+            return None;
+        }
+
+        Some(first.with_value(first.value.text_range().cover(last.value.text_range())))
+    })?)
+}
+
+fn ascend_call_token(
+    db: &dyn HirDatabase,
+    expansion: &ExpansionInfo,
+    token: InFile<SyntaxToken>,
+) -> Option<InFile<SyntaxToken>> {
+    let (mapped, origin) = expansion.map_token_up(token.as_ref())?;
+    if origin != Origin::Call {
+        return None;
+    }
+    if let Some(info) = mapped.file_id.expansion_info(db.upcast()) {
+        return ascend_call_token(db, &info, mapped);
+    }
+    Some(mapped)
+}