OOM in explorer type checking when a function with infinite recursion is specified in another function's return type

[pk19604014]

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$ cat /tmp/crash.carbon package P api;

fn g() -> Bool { return g(); }

fn f() -> g() { }

fn Main() -> i32 { return 0; }

$ time bazel run explorer:explorer /tmp/crash.carbon ...eventually OOMs real 45m43.497s user 33m10.615s sys 6m2.100s

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[chandlerc]

Closing explorer-specific issues as not-planned for now due to our decision to prioritize working on the toolchain over other implementation work in the near term: https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p3532.md