Can the optimizer assume that a borrow lifetime dependence never writes to its source?

Hello, I've been looking into swiftlang/swift#91665, which is a dead swift_bridgeObjectRelease that gets left behind in a hot String to Span loop, and I ended up with a fix that depends on a semantic assumption I can't find written down anywhere, so I figured I should ask instead of guessing. The short version of what goes wrong is that an escape walk gives up, and once it gives up AliasAnalysis.getApplyEffect (AliasAnalysis.swift:418) falls back to the global effects of the callee, which ...