Pointer types

Canonical guidance

• *T is a distinct type from T
• not every expression is addressable
• pointer receiver calls may work through addressable values, but interface method sets still matter

Use when

• reasoning about mutation through references
• checking whether &x or *p is legal
• explaining nil pointer panics or method call legality

Avoid

• using pointers for small immutable values without semantic benefit
• assuming maps or interface values are addressable
• conflating pointer convenience with interface satisfaction

Preferred pattern

type Counter struct {
	n int
}

func (c *Counter) Inc() { c.n++ }

Anti-pattern

• taking the address of a map element

Explanation: This is tempting because the element looks like an lvalue, but map indexing does not produce an addressable value.

Why

• pointer rules interact with method calls, interfaces, and panics in ways agents need to retrieve precisely