Spec Update: Batch 04 — Expressions

Date: 2026-04-16 Plans Referenced: Plan 026 (property keywords), Plan 060 (closures), Plan 095 (compile-time), Plan 120 (Option/Result), Plan 122 (ownership), Plan 124 (async), Plan 126 (micro-concurrency), Plan 161/162/165 (various expr enhancements) Source Files: ast.rs (Expr enum, 55 variants) Sections Updated: Expressions (Section 6) — major rewrite

Old Content

Old Expressions section had 10 subsections covering basic expressions only:

• Literal, Identifier, Binary (Arithmetic/Comparison/Logical), Assignment, Range, F-String, Array, Object, Grouping

New Content

Expanded to 22 subsections covering all 55 Expr variants:

• Literal: added u, u8, i8, i64, d, C-string (c"...")
• Arithmetic: added modulo %
• Logical: added and/or keyword forms
• Assignment: added %=
• Ownership: .view, .mut, .move (Plan 122)
• Type Conversion: .as(Type), .to(Type) (zero-cost reinterpret vs explicit conversion)
• Option/Result: Some(v), None, Ok(v), Err(e), ??, .?, ?. (Plan 120)
• Closures: (a, b) => expr, x => expr (Plan 060)
• If expressions: as value-producing expressions
• Block expressions: last expression is the value
• Null coalescing: ?? operator
• Error propagation: .? operator
• Smart pointers: Box(value), Arc(value)
• Async: ~{ } blocks, .await, .go (Plans 124/126)
• Compile-time: #{ expr } (Plan 095)
• Node: widget construction
• Grid: tabular data
• Hold: lifetime extension
• Precedence table: 11 levels from highest to lowest

Notes

• F-string examples updated to use $name (Auto syntax) not {name} (Rust syntax)
• Take expr variant is DEPRECATED — use Move instead
• Cover/Uncover/OptionPattern/ResultPattern/StructPattern variants are pattern-matching related; documented in Control Flow section
• NavCall variant is routing-specific; documented in UI/Routing section
• GenName is internal (generated names not in symbol table); not user-facing