v5 Parsing: modules + member access

Compile unit behavior

• If first token is module, parse full module mode.
• Otherwise, wrap statement stream into implicit module main.
• In module mode, parse moduleItem* until closing }.

Module-level declarations

• Module header: module IDENT { ... }
• Imports are module items only.
• Import alias defaults to the module name.
• import name as alias; is valid; trailing ; is required.

Export contract

• export only wraps declaration nodes.
• valid: export fn ..., export let/var/const ...
• invalid export target should error as declaration mismatch.

Postfix chain strategy

postfix -> primary (call | index | member)*

• chain is left-to-right
• member adds ExprMember with Value = identifier
• member is parsed via a . IDENT, where IDENT is mandatory

Assignment target rule

• valid assignment target kinds: identifier and index
• ExprMember is intentionally not a valid left side in v5 parser

AST additions

• Program.Modules []*Module
• Module{Name, Imports, Stmts}
• Import{Name, Alias}
• Stmt.Exported bool
• ExprMember node