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go.slice_append_in_loop

Performance Low

Detects slice appends in loops without pre-allocation, causing repeated reallocations.

Why It Matters

Appending without pre-allocation:

Multiple reallocations — Slice grows exponentially, copying each time
Memory churn — Old backing arrays become garbage
GC pressure — More work for garbage collector

Example

// ❌ Before (grows slice repeatedly)
var result []Item
for _, id := range ids {
    result = append(result, fetchItem(id))
}

// ✅ After (pre-allocated)
result := make([]Item, 0, len(ids))
for _, id := range ids {
    result = append(result, fetchItem(id))
}

What Unfault Detects

append() in loops without make([]T, 0, n) initialization
Growing slices without capacity hint when size is known

Auto-Fix

Unfault adds slice pre-allocation:

result := make([]Item, 0, len(ids))