1 files changed, 183 insertions, 0 deletions

diff --git a/crates/libeditor/src/scope.rs b/crates/libeditor/src/scope.rs
new file mode 100644
index 000000000..1fec0b24e
--- /dev/null
+++ b/crates/libeditor/src/scope.rs
@@ -0,0 +1,183 @@
+use std::{
+    fmt,
+    collections::HashMap,
+};
+
+use libsyntax2::{
+    SyntaxNodeRef, SyntaxNode, SmolStr, AstNode,
+    ast::{self, NameOwner},
+    algo::{ancestors, generate, walk::preorder}
+};
+
+pub 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));
+
+    if let Some(body) = fn_def.body() {
+        compute_block_scopes(body, &mut scopes, root)
+    }
+    scopes
+}
+
+fn compute_block_scopes(block: ast::Block, scopes: &mut FnScopes, mut scope: ScopeId) {
+    for stmt in block.statements() {
+        match stmt {
+            ast::Stmt::LetStmt(stmt) => {
+                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)
+                }
+            }
+            ast::Stmt::ExprStmt(expr_stmt) => {
+                if let Some(expr) = expr_stmt.expr() {
+                    scopes.set_scope(expr.syntax(), scope);
+                    compute_expr_scopes(expr, scopes, scope);
+                }
+            }
+        }
+    }
+    if let Some(expr) = block.expr() {
+        scopes.set_scope(expr.syntax(), scope);
+        compute_expr_scopes(expr, scopes, scope);
+    }
+}
+
+fn compute_expr_scopes(expr: ast::Expr, scopes: &mut FnScopes, scope: ScopeId) {
+    match expr {
+        ast::Expr::IfExpr(e) => {
+            let cond_scope = e.condition().and_then(|cond| {
+                compute_cond_scopes(cond, scopes, scope)
+            });
+            if let Some(block) = e.then_branch() {
+                compute_block_scopes(block, scopes, cond_scope.unwrap_or(scope));
+            }
+            if let Some(block) = e.else_branch() {
+                compute_block_scopes(block, scopes, scope);
+            }
+        },
+        ast::Expr::WhileExpr(e) => {
+            let cond_scope = e.condition().and_then(|cond| {
+                compute_cond_scopes(cond, scopes, scope)
+            });
+            if let Some(block) = e.body() {
+                compute_block_scopes(block, scopes, cond_scope.unwrap_or(scope));
+            }
+        },
+        ast::Expr::BlockExpr(e) => {
+            if let Some(block) = e.block() {
+                compute_block_scopes(block, scopes, scope);
+            }
+        }
+        // ForExpr(e) => TODO,
+        _ => {
+            expr.syntax().children()
+                .filter_map(ast::Expr::cast)
+                .for_each(|expr| compute_expr_scopes(expr, scopes, scope))
+        }
+    };
+
+    fn compute_cond_scopes(cond: ast::Condition, scopes: &mut FnScopes, scope: ScopeId) -> Option<ScopeId> {
+        if let Some(expr) = cond.expr() {
+            compute_expr_scopes(expr, scopes, scope);
+        }
+        if let Some(pat) = cond.pat() {
+            let s = scopes.new_scope(scope);
+            scopes.add_bindings(s, pat);
+            Some(s)
+        } else {
+            None
+        }
+    }
+}
+
+type ScopeId = usize;
+
+#[derive(Debug)]
+pub struct FnScopes {
+    scopes: Vec<ScopeData>,
+    scope_for: HashMap<SyntaxNode, ScopeId>,
+}
+
+impl FnScopes {
+    fn new() -> FnScopes {
+        FnScopes {
+            scopes: vec![],
+            scope_for: HashMap::new(),
+        }
+    }
+    pub fn entries(&self, scope: ScopeId) -> &[ScopeEntry] {
+        &self.scopes[scope].entries
+    }
+    pub 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 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 scope_for(&self, node: SyntaxNodeRef) -> Option<ScopeId> {
+        ancestors(node)
+            .filter_map(|it| self.scope_for.get(&it.owned()).map(|&scope| scope))
+            .next()
+    }
+}
+
+#[derive(Debug)]
+struct ScopeData {
+    parent: Option<ScopeId>,
+    entries: Vec<ScopeEntry>
+}
+
+pub 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
+        }
+    }
+    pub fn name(&self) -> SmolStr {
+        self.ast().name()
+            .unwrap()
+            .text()
+    }
+    fn ast(&self) -> ast::BindPat {
+        ast::BindPat::cast(self.syntax.borrowed())
+            .unwrap()
+    }
+}
+
+impl fmt::Debug for ScopeEntry {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("ScopeEntry")
+         .field("name", &self.name())
+         .field("syntax", &self.syntax)
+         .finish()
+    }
+}