7 files changed, 155 insertions, 75 deletions

diff --git a/crates/libeditor/src/completion.rs b/crates/libeditor/src/completion.rs
index 351781ec4..6335dba17 100644
--- a/crates/libeditor/src/completion.rs
+++ b/crates/libeditor/src/completion.rs
@@ -7,6 +7,7 @@ use libsyntax2::{
         ancestors,
         visit::{visitor_ctx, VisitorCtx},
         walk::preorder,
+        generate,
     },
 };
 
@@ -27,86 +28,125 @@ pub fn scope_completion(file: &File, offset: TextUnit) -> Option<Vec<CompletionI
         file.incremental_reparse(&edit)?
     };
     let name_ref = find_node_at_offset::<ast::NameRef>(file.syntax(), offset)?;
-    Some(complete(name_ref))
+    let fn_def = ancestors(name_ref.syntax()).filter_map(ast::FnDef::cast).next()?;
+    let scopes = compute_scopes(fn_def);
+    Some(complete(name_ref, &scopes))
 }
 
-fn complete(name_ref: ast::NameRef) -> Vec<CompletionItem> {
-    let mut res = Vec::new();
-    for node in ancestors(name_ref.syntax()) {
-        process_scope(node, &mut res);
-    }
-    res
-}
-
-fn process_scope(node: SyntaxNodeRef, sink: &mut Vec<CompletionItem>) {
-    let _ = visitor_ctx(sink)
-        .visit::<ast::Block, _>(|block, sink| {
-            block.let_stmts()
-                .filter_map(|it| it.pat())
-                .for_each(move |it| process_pat(it, sink))
-        })
-        .visit::<ast::FnDef, _>(|fn_def, sink| {
-            fn_def.param_list().into_iter()
-                .flat_map(|it| it.params())
-                .filter_map(|it| it.pat())
-                .for_each(move |it| process_pat(it, sink))
+fn complete(name_ref: ast::NameRef, scopes: &FnScopes) -> Vec<CompletionItem> {
+    scopes.scope_chain(name_ref.syntax())
+        .flat_map(|scope| scopes.entries(scope).iter())
+        .map(|entry| CompletionItem {
+            name: entry.name().to_string()
         })
-        .accept(node);
+        .collect()
+}
 
-    fn process_pat(pat: ast::Pat, sink: &mut Vec<CompletionItem>) {
-        let items = preorder(pat.syntax())
-            .filter_map(ast::BindPat::cast)
-            .filter_map(ast::BindPat::name)
-            .map(|name| CompletionItem { name: name.text().to_string() });
-        sink.extend(items);
+fn compute_scopes(fn_def: ast::FnDef) -> FnScopes {
+    let mut scopes = FnScopes::new();
+    let root = scopes.root_scope();
+    fn_def.param_list().into_iter()
+        .flat_map(|it| it.params())
+        .filter_map(|it| it.pat())
+        .for_each(|it| scopes.add_bindings(root, it));
+
+    let mut scope = root;
+    if let Some(body) = fn_def.body() {
+        for child in body.syntax().children() {
+            let _ = visitor_ctx((&mut scopes, &mut scope))
+                .visit::<ast::LetStmt, _>(|stmt, (scopes, scope)| {
+                    *scope = scopes.new_scope(*scope);
+                    if let Some(pat) = stmt.pat() {
+                        scopes.add_bindings(*scope, pat);
+                    }
+                    if let Some(expr) = stmt.initializer() {
+                        scopes.set_scope(expr.syntax(), *scope)
+                    }
+                })
+                .visit::<ast::ExprStmt, _>(|expr, (scopes, scope)| {
+                    scopes.set_scope(expr.syntax(), *scope)
+                })
+                .visit::<ast::Expr, _>(|expr, (scopes, scope)| {
+                    scopes.set_scope(expr.syntax(), *scope)
+                })
+                .accept(child);
+        }
     }
+    scopes
 }
 
-// fn compute_scopes(fn_def: ast::FnDef) -> FnScopes {
-//     let mut scopes = FnScopes::new();
-// }
-
-// type ScopeId = usize;
+type ScopeId = usize;
 
-// struct FnScopes {
-//     scopes: Vec<ScopeData>,
-//     scope_for_expr: HashMap<SyntaxNode, ScopeId>,
-// }
-
-// impl FnScopes {
-//     fn new() -> FnScopes {
-//         FnScopes {
-//             scopes: vec![],
-//             scope_for_expr: HashMap::new(),
-//         }
-//     }
+struct FnScopes {
+    scopes: Vec<ScopeData>,
+    scope_for: HashMap<SyntaxNode, ScopeId>,
+}
 
-//     fn new_scope(&mut Self) -> ScopeId {
-//         let res = self.scopes.len();
-//         self.scopes.push(ScopeData { parent: None, entries: vec![] })
-//     }
+impl FnScopes {
+    fn new() -> FnScopes {
+        FnScopes {
+            scopes: vec![],
+            scope_for: HashMap::new(),
+        }
+    }
+    fn root_scope(&mut self) -> ScopeId {
+        let res = self.scopes.len();
+        self.scopes.push(ScopeData { parent: None, entries: vec![] });
+        res
+    }
+    fn new_scope(&mut self, parent: ScopeId) -> ScopeId {
+        let res = self.scopes.len();
+        self.scopes.push(ScopeData { parent: Some(parent), entries: vec![] });
+        res
+    }
+    fn add_bindings(&mut self, scope: ScopeId, pat: ast::Pat) {
+        let entries = preorder(pat.syntax())
+            .filter_map(ast::BindPat::cast)
+            .filter_map(ScopeEntry::new);
+        self.scopes[scope].entries.extend(entries);
+    }
+    fn set_scope(&mut self, node: SyntaxNodeRef, scope: ScopeId) {
+        self.scope_for.insert(node.owned(), scope);
+    }
+    fn entries(&self, scope: ScopeId) -> &[ScopeEntry] {
+        &self.scopes[scope].entries
+    }
+    fn scope_for(&self, node: SyntaxNodeRef) -> Option<ScopeId> {
+        ancestors(node)
+            .filter_map(|it| self.scope_for.get(&it.owned()).map(|&scope| scope))
+            .next()
+    }
+    fn scope_chain<'a>(&'a self, node: SyntaxNodeRef) -> impl Iterator<Item=ScopeId> + 'a {
+        generate(self.scope_for(node), move |&scope| self.scopes[scope].parent)
+    }
+}
 
-//     fn set_parent
-// }
+struct ScopeData {
+    parent: Option<ScopeId>,
+    entries: Vec<ScopeEntry>
+}
 
-// struct ScopeData {
-//     parent: Option<ScopeId>,
-//     entries: Vec<ScopeEntry>
-// }
+struct ScopeEntry {
+    syntax: SyntaxNode
+}
 
-// struct ScopeEntry {
-//     syntax: SyntaxNode
-// }
+impl ScopeEntry {
+    fn new(pat: ast::BindPat) -> Option<ScopeEntry> {
+        if pat.name().is_some() {
+            Some(ScopeEntry { syntax: pat.syntax().owned() })
+        } else {
+            None
+        }
+    }
 
-// impl ScopeEntry {
-//     fn name(&self) -> SmolStr {
-//         self.ast().name()
-//             .unwrap()
-//             .text()
-//     }
+    fn name(&self) -> SmolStr {
+        self.ast().name()
+            .unwrap()
+            .text()
+    }
 
-//     fn ast(&self) -> ast::BindPat {
-//         ast::BindPat::cast(self.syntax.borrowed())
-//             .unwrap()
-//     }
-// }
+    fn ast(&self) -> ast::BindPat {
+        ast::BindPat::cast(self.syntax.borrowed())
+            .unwrap()
+    }
+}
diff --git a/crates/libeditor/tests/test.rs b/crates/libeditor/tests/test.rs
index ecdc149c7..7979bfffe 100644
--- a/crates/libeditor/tests/test.rs
+++ b/crates/libeditor/tests/test.rs
@@ -268,7 +268,8 @@ fn test_completion() {
     do_check(r"
 fn quux(x: i32) {
     let y = 92;
-    1 + <|>
+    1 + <|>;
+    let z = ();
 }
 ", r#"[CompletionItem { name: "y" },
        CompletionItem { name: "x" }]"#);
diff --git a/crates/libsyntax2/src/algo/mod.rs b/crates/libsyntax2/src/algo/mod.rs
index 2640d60ea..7287f5bb2 100644
--- a/crates/libsyntax2/src/algo/mod.rs
+++ b/crates/libsyntax2/src/algo/mod.rs
@@ -119,7 +119,7 @@ fn common_ancestor<'a>(n1: SyntaxNodeRef<'a>, n2: SyntaxNodeRef<'a>) -> SyntaxNo
     panic!("Can't find common ancestor of {:?} and {:?}", n1, n2)
 }
 
-fn generate<T>(seed: Option<T>, step: impl Fn(&T) -> Option<T>) -> impl Iterator<Item=T> {
+pub fn generate<T>(seed: Option<T>, step: impl Fn(&T) -> Option<T>) -> impl Iterator<Item=T> {
     ::itertools::unfold(seed, move |slot| {
         slot.take().map(|curr| {
             *slot = step(&curr);
diff --git a/crates/libsyntax2/src/ast/generated.rs b/crates/libsyntax2/src/ast/generated.rs
index 6926c0535..b937fe5a2 100644
--- a/crates/libsyntax2/src/ast/generated.rs
+++ b/crates/libsyntax2/src/ast/generated.rs
@@ -383,6 +383,24 @@ impl<'a> AstNode<'a> for Expr<'a> {
 
 impl<'a> Expr<'a> {}
 
+// ExprStmt
+#[derive(Debug, Clone, Copy)]
+pub struct ExprStmt<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for ExprStmt<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            EXPR_STMT => Some(ExprStmt { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> ExprStmt<'a> {}
+
 // FieldExpr
 #[derive(Debug, Clone, Copy)]
 pub struct FieldExpr<'a> {
@@ -442,6 +460,10 @@ impl<'a> FnDef<'a> {
     pub fn param_list(self) -> Option<ParamList<'a>> {
         super::child_opt(self)
     }
+
+    pub fn body(self) -> Option<Block<'a>> {
+        super::child_opt(self)
+    }
 }
 
 // FnPointerType
@@ -626,6 +648,10 @@ impl<'a> LetStmt<'a> {
     pub fn pat(self) -> Option<Pat<'a>> {
         super::child_opt(self)
     }
+
+    pub fn initializer(self) -> Option<Expr<'a>> {
+        super::child_opt(self)
+    }
 }
 
 // LoopExpr
diff --git a/crates/libsyntax2/src/grammar.ron b/crates/libsyntax2/src/grammar.ron
index 3a125ace6..aa2742b3e 100644
--- a/crates/libsyntax2/src/grammar.ron
+++ b/crates/libsyntax2/src/grammar.ron
@@ -248,7 +248,8 @@ Grammar(
                 "AttrsOwner",
             ],
             options: [
-                ["param_list", "ParamList"]
+                ["param_list", "ParamList"],
+                ["body", "Block"],
             ],
         ),
         "StructDef": (
@@ -431,7 +432,11 @@ Grammar(
         "TypeParamList": ( collections: [ ["type_params", "TypeParam" ] ]),
         "TypeParam": ( traits: ["NameOwner"] ),
         "WhereClause": (),
-        "LetStmt": ( options: [ ["pat", "Pat"] ]),
+        "ExprStmt": (),
+        "LetStmt": ( options: [
+            ["pat", "Pat"],
+            ["initializer", "Expr"],
+        ]),
         "Block": (
             collections: [
                 ["let_stmts", "LetStmt"],
diff --git a/crates/libsyntax2/src/yellow/mod.rs b/crates/libsyntax2/src/yellow/mod.rs
index 3c4510fe7..b94c794fe 100644
--- a/crates/libsyntax2/src/yellow/mod.rs
+++ b/crates/libsyntax2/src/yellow/mod.rs
@@ -66,7 +66,7 @@ impl SyntaxRoot {
     }
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
 pub(crate) struct RedPtr(ptr::NonNull<RedNode>);
 
 unsafe impl Send for RedPtr {}
diff --git a/crates/libsyntax2/src/yellow/syntax.rs b/crates/libsyntax2/src/yellow/syntax.rs
index 0045598d4..75b6cb7dc 100644
--- a/crates/libsyntax2/src/yellow/syntax.rs
+++ b/crates/libsyntax2/src/yellow/syntax.rs
@@ -1,4 +1,7 @@
-use std::{fmt, sync::Arc};
+use std::{
+    fmt, sync::Arc,
+    hash::{Hasher, Hash},
+};
 
 use smol_str::SmolStr;
 
@@ -27,6 +30,11 @@ impl<R1: TreeRoot, R2: TreeRoot> PartialEq<SyntaxNode<R1>> for SyntaxNode<R2> {
 }
 
 impl<R: TreeRoot> Eq for SyntaxNode<R> {}
+impl<R: TreeRoot> Hash for SyntaxNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.red.hash(state)
+    }
+}
 
 pub type SyntaxNodeRef<'a> = SyntaxNode<RefRoot<'a>>;