SR-7380, Ambiguous KeyPath

Matt Diephouse:

Here’s the bug I fixed (with a lot of help):

7380.swift:1:16: error: type of expression is ambiguous without more context
"str"[keyPath: \.count]
               ^~~~~~~

That seems obviously broken. The value is a String literal. They KeyPath should obviously be String.count. So why doesn’t this work?

This is an interesting look at learning how to fix a bug in the Swift compiler.

Compiler Programming Swift Programming Language

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