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LibJS: Evaluate for statements in their own scope if necessary

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We now evaluate for loops in their own scope if their init statement is
a lexical declaration.

Evaluating for loops in their own scope allow us to obtain expected
behaviour, which means for example, that the block-scoped variables
declared in a  for statement will be limited to the scope of the for
loop's body and  statement and not to that of the current scope (i.e the
one where the for statement was made)
This commit is contained in:
0xtechnobabble 2020-03-14 13:56:49 +02:00 • committed by Andreas Kling
parent 0659d07241
commit 644b4f4201
4 changed files with 17 additions and 3 deletions
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10
Libraries/LibJS/AST.cpp
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@ -95,6 +95,13 @@ Value WhileStatement::execute(Interpreter& interpreter) const
Value ForStatement::execute(Interpreter& interpreter) const
{
OwnPtr<BlockStatement> wrapper;
if (m_init->is_variable_declaration() && static_cast<const VariableDeclaration*>(m_init.ptr())->declaration_type() != DeclarationType::Var) {
wrapper = make<BlockStatement>();
interpreter.enter_scope(*wrapper, {}, ScopeType::Block);
}
Value last_value = js_undefined();
if (m_init)
@ -114,6 +121,9 @@ Value ForStatement::execute(Interpreter& interpreter) const
}
}
if (wrapper)
interpreter.exit_scope(*wrapper);
return last_value;
}