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They return nil only when start exceeds the stack depth, which almost never happens in practice (even at the top level, caller(1) returns []). Treating the result as non-nil lets common idioms such as caller_locations(1, 1).first type-check without a nil guard, matching Exception#backtrace. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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The argument overloads of
Kernel#caller/Kernel#caller_locationsreturnnilonly whenstartexceeds the stack depth. Even at the top level,caller(1)returns[];nilappears only forcaller(2)or larger there, so in practice it signals a programming mistake rather than a meaningful branch.This PR switches those overloads from
Array[...]?to%a{implicitly-returns-nil} ... -> Array[...], followingException#backtrace/#backtrace_locations. Common idioms such ascaller_locations(1, 1).firstthen type-check without a nil guard.Array#[]keeps(int start, int length) -> Array[E]?because slicing arbitrary arrays with computed indices can legitimately go out of range.callerslices the call stack, usually with a small literalstart, so it is closer to theException#backtracecase.The existing nil-case tests in
test/stdlib/Kernel_test.rb(caller(100000)etc.) cover this: they pass with the annotation and fail without it.🤖 Generated with Claude Code