AST request evaluator problems

Hi @Douglas_Gregor,

I'm trying to debug a problem and the AST request evaluator is getting in the way by causing Decl::dump() to crash in code synthesis diagnostics. Does this surprise you? Is this expected?

If you want to reproduce this, try adding var->dump() to the top of PropertyWrapperBackingPropertyTypeRequest::evaluate() and then running test/decl/var/property_wrappers.swift from the test suite. This crash perfectly mimics the bug I'm trying to figure out (with the same test case).

Workaround (or fix?): [CodeSynth] NFC: Simplify diagnostic output by davezarzycki · Pull Request #26408 · apple/swift · GitHub