Built-in functions

Canonical guidance

• built-ins are special forms defined by the language
• make and new solve different problems
• append, copy, delete, clear, close, len, and cap all have operand-specific rules

Use when

• checking legality of a built-in call
• reasoning about allocation or zeroing
• reviewing slice, map, and channel manipulation

Avoid

• treating built-ins like interchangeable helpers
• using new([]T) when make([]T, n) is intended
• assuming append or copy implies ownership isolation automatically

Preferred pattern

buf := make([]byte, 0, 1024)
buf = append(buf, data...)

Anti-pattern

• using new(map[string]int) when the code actually needs an initialized map ready for writes

Explanation: This is tempting because both forms allocate something, but new and make produce different kinds of values with different readiness for use.

Why

• built-ins sit on many of Go’s core semantics: allocation, capacity, maps, channels, panics, and copying