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LibJS: Hoist variable declarations to the nearest relevant scope

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"var" declarations are hoisted to the nearest function scope, while
"let" and "const" are hoisted to the nearest block scope.

This is done by the parser, which keeps two scope stacks, one stack
for the current var scope and one for the current let/const scope.

When the interpreter enters a scope, we walk all of the declarations
and insert them into the variable environment.

We don't support the temporal dead zone for let/const yet.
This commit is contained in:
Andreas Kling 2020-04-13 16:42:54 +02:00
parent b9415dc0e9
commit ac7459cb40
7 changed files with 158 additions and 21 deletions
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24
Libraries/LibJS/AST.h
View file

@ -38,6 +38,8 @@
namespace JS {
class VariableDeclaration;
template<class T, class... Args>
static inline NonnullRefPtr<T>
create_ast_node(Args&&... args)
@ -54,6 +56,7 @@ public:
virtual bool is_identifier() const { return false; }
virtual bool is_member_expression() const { return false; }
virtual bool is_scope_node() const { return false; }
virtual bool is_program() const { return false; }
virtual bool is_variable_declaration() const { return false; }
virtual bool is_new_expression() const { return false; }
@ -105,12 +108,16 @@ public:
virtual Value execute(Interpreter&) const override;
virtual void dump(int indent) const override;
void add_variables(NonnullRefPtrVector<VariableDeclaration>);
const NonnullRefPtrVector<VariableDeclaration>& variables() const { return m_variables; }
protected:
ScopeNode() {}
private:
virtual bool is_scope_node() const final { return true; }
NonnullRefPtrVector<Statement> m_children;
NonnullRefPtrVector<VariableDeclaration> m_variables;
};
class Program : public ScopeNode {
@ -118,6 +125,7 @@ public:
Program() {}
private:
virtual bool is_program() const override { return true; }
virtual const char* class_name() const override { return "Program"; }
};
@ -142,19 +150,23 @@ public:
const Vector<FlyString>& parameters() const { return m_parameters; };
protected:
FunctionNode(const FlyString& name, NonnullRefPtr<Statement> body, Vector<FlyString> parameters = {})
FunctionNode(const FlyString& name, NonnullRefPtr<Statement> body, Vector<FlyString> parameters, NonnullRefPtrVector<VariableDeclaration> variables)
: m_name(name)
, m_body(move(body))
, m_parameters(move(parameters))
, m_variables(move(variables))
{
}
void dump(int indent, const char* class_name) const;
const NonnullRefPtrVector<VariableDeclaration>& variables() const { return m_variables; }
private:
FlyString m_name;
NonnullRefPtr<Statement> m_body;
const Vector<FlyString> m_parameters;
NonnullRefPtrVector<VariableDeclaration> m_variables;
};
class FunctionDeclaration final
@ -163,8 +175,8 @@ class FunctionDeclaration final
public:
static bool must_have_name() { return true; }
FunctionDeclaration(const FlyString& name, NonnullRefPtr<Statement> body, Vector<FlyString> parameters = {})
: FunctionNode(name, move(body), move(parameters))
FunctionDeclaration(const FlyString& name, NonnullRefPtr<Statement> body, Vector<FlyString> parameters, NonnullRefPtrVector<VariableDeclaration> variables)
: FunctionNode(name, move(body), move(parameters), move(variables))
{
}
@ -180,8 +192,8 @@ class FunctionExpression final : public Expression
public:
static bool must_have_name() { return false; }
FunctionExpression(const FlyString& name, NonnullRefPtr<Statement> body, Vector<FlyString> parameters = {})
: FunctionNode(name, move(body), move(parameters))
FunctionExpression(const FlyString& name, NonnullRefPtr<Statement> body, Vector<FlyString> parameters, NonnullRefPtrVector<VariableDeclaration> variables)
: FunctionNode(name, move(body), move(parameters), move(variables))
{
}
@ -641,6 +653,8 @@ public:
virtual Value execute(Interpreter&) const override;
virtual void dump(int indent) const override;
const NonnullRefPtrVector<VariableDeclarator>& declarations() const { return m_declarations; }
private:
virtual const char* class_name() const override { return "VariableDeclaration"; }