18 lines
2.2 KiB
Markdown
18 lines
2.2 KiB
Markdown
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---
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name: Prefer check() over silent-skip for invariants
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description: In C++ code, when a condition is an invariant that should always hold (not a legitimate filter), use check() instead of a silent continue/return that hides the bug
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type: feedback
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originSessionId: a2780d4f-894b-402a-8101-324052832606
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---
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When writing C++ code in this project, if a condition represents an **invariant** (something that must always be true based on how the code is structured), use `check()` to assert it — do **not** silently `continue`/`return`/guard past it.
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**Why:** Silent skips conceal bugs. If the invariant is ever violated, the code just mysteriously produces a shorter list, a missing widget, a zero count — with no signal that anything went wrong. `check()` fails loudly and makes the broken invariant visible and diagnosable. The user has articulated this as a general principle: "I am strongly against code that hides bugs by failing silently."
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**How to apply:**
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- **Invariant → `check()`**: something that must hold given how the code is wired AND a violation would propagate silently (stored in a container, passed to a function that tolerates null, absorbed by a later filter). Example: pushing a potentially-null pointer into a TSet or TArray — segfault won't happen until much later.
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- **Invariant about to be dereferenced → nothing**: if the very next line dereferences the pointer, a null will segfault on its own. That IS a loud failure. Don't add a `check()` just for style — the segfault is the check. Also don't add checks for things that were *just constructed* and cannot be null in any realistic scenario ("we just built this array").
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- **Legitimate filter → `if (...) continue;`**: a real business-logic condition that may or may not hold for different inputs. Example: filtering `Slots` to only those whose `Content` is a `UUserWidget` — other widget types are legitimate children, so skipping them is a filter, not hiding a bug.
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- When in doubt, ask: "If this condition is false, is that a bug? AND will the bug propagate silently?" Only `check()` when BOTH are true.
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Related: [LLDB formatter style — no defensive IsValid checks](feedback_lldb_formatter_no_defensive_checks.md) is the same principle applied specifically to lldb SBValue chains.
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