Expand description
Node: cxx:Method:Luau.Ast:Ast/src/Parser.cpp:2004:parseAssignment
Faithful port of Parser::parseAssignment — var {, var} = expr {, expr}.
Each assignment target is validated as an l-value (a non-l-value is replaced
by an error node, gated on the export-value flag pair like the C++). The
target and value lists are gathered in scratch arenas (vars/values share the
comma-position arena, stack-disciplined) and copied into the node.