More precise type for typed patterns, less precise for literal patterns #8710
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In `x @ Nil`, `Nil` is a _stable identifier pattern_ and will be compiled to an `==` test, so the type of `x` is unrelated to the type of `Nil`. This was handled correctly before this commit, but the check to use the moe restrictive patten typing was too wide and also included typed patterns like `x: Nil.type`, even though such patterns compile to `eq` tests and therefore it's safe to assume that `x` has type `Nil.type`. Additionally, a _literal pattern_ will also be compiled to an `==` test and therefore should be less precisely typed, like a stable identifier patterns.
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In
x @ Nil,Nilis a stable identifier pattern and will be compiledto an
==test, so the type ofxis unrelated to the type ofNil.This was handled correctly before this commit, but the check to use the
moe restrictive patten typing was too wide and also included typed
patterns like
x: Nil.type, even though such patterns compile toeqtests and therefore it's safe to assume that
xhas typeNil.type.Additionally, a literal pattern will also be compiled to an
==testand therefore should be less precisely typed, like a stable identifier
patterns.