Use case
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How to Inspect an Autocomplete Completion
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Published by Unrust. Scoring and editorial method
Quick answer
Inspect an autocomplete completion before accepting it by reading the code immediately around the cursor and asking what the missing lines must guarantee. Check whether the completion creates a new value or mutation, adds a default, catches an error, or invokes an API with an assumed signature. A completion can save typing, but only the surrounding contract tells you whether its behavior is appropriate.
Use the cursor location as evidence, not instruction
The position of a suggestion tells you where text might fit, not what the program needs. Look at the function name, types, callers, and tests around the gap, then decide whether the proposed branch, helper, or expression preserves the intended relationship between input and output.
Inspect defaults and side effects
Short completions often introduce the most consequential decisions in a compact form: a fallback value, a mutation, a swallowed exception, or an extra request. Expand those decisions mentally and verify their behavior with a focused test instead of accepting them because the syntax looks conventional.
Check the loop's final boundary
Copy every item of a dense array in order, without adding another item. Trace the completed loop for a one-item array and for an empty array before accepting it.
The inclusive boundary reads one position beyond the end and appends undefined. The strict boundary matches the valid index interval. This does not cover sparse arrays or getters; those need their own behavior contract.
The outcomes below are checked by executable tests against the exact displayed snippets. NaN and undefined are written by name so they remain visible in the table.
function run(items) {
const result = [];
for (let i = 0; i <= items.length; i += 1) result.push(items[i]);
return result;
}function run(items) {
const result = [];
for (let i = 0; i < items.length; i += 1) result.push(items[i]);
return result;
}| Arguments to run | Before | After |
|---|---|---|
| ["a"] | ["a", undefined] | ["a"] |
| [] | [undefined] | [] |
Practice loop
- 01Read the enclosing function and state its input-output contract before accepting a completion.
- 02Identify one default, mutation, or error path implied by the suggested code.
- 03Run a small test that distinguishes the suggestion from the simplest no-op alternative.
Limits of this page
Autocomplete quality and codebase conventions vary widely, so this page cannot supply a universal accept-or-reject rule. A short unassisted check is only a snapshot and cannot distinguish a recall lapse from an unfamiliar framework, a rushed review, or a poorly framed task.
Source context
Published by Unrust as practical teaching material using public language documentation and original examples. See the scoring and editorial method for scope, checking and limitations.
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