[PATCH] D85611: Improve dynamic AST matching diagnostics for conversion errors

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman created this revision.
aaron.ballman added reviewers: steveire, sbenza, klimek, sammccall.
aaron.ballman requested review of this revision.

Currently, when marshaling a dynamic AST matchers, we check for the type and value validity of matcher arguments at the same time for some matchers. For instance, when marshaling `hasAttr("foo")`, the argument is first type checked to ensure it's a string and then checked to see if that string can locate an attribute with that name. Similar happens for other enumeration conversions like cast kinds or unary operator kinds. If the type is correct but the value cannot be looked up, we make a best-effort attempt to find a nearby name that the user might have meant, but if one cannot be found, we throw our hands up and claim the types don't match.

This has an unfortunate behavior that when the user enters something of the correct type but a best guess cannot be located, you get confusing error messages like: `Incorrect type for arg 1. (Expected = string) != (Actual = String)`.

This patch splits the argument check into two parts: if the types don't match, give a type diagnostic. If the type matches but the value cannot be converted, give a best guess diagnostic or a value could not be located diagnostic:

  clang-query> m hasAttr("cool")
  1:1: Error building matcher hasAttr.
  1:9: Value not found: cool
  clang-query> m hasAttr("attr::cool")
  1:1: Error building matcher hasAttr.
  1:9: Unknown value 'attr::cool' for arg 1; did you mean 'attr::Cold'

This addresses PR47057.


https://reviews.llvm.org/D85611

Files:
  clang/lib/ASTMatchers/Dynamic/Marshallers.h
  clang/unittests/ASTMatchers/Dynamic/ParserTest.cpp

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