[clang] [Clang][Preprocessor] Unify header-name lookahead for import and include (PR #191004)

[Richard Smith via cfe-commits]

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@@ -4677,7 +4676,10 @@ bool Lexer::LexDependencyDirectiveToken(Token &Result) {
 
   if (ParsingFilename && DDTok.is(tok::less)) {
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zygoloid wrote:

This looks wrong. If we can't lex the token correctly from the start (can we?) then we'll need to relex any token that starts with `<`. Why are we in a situation where we mislexed the token?

https://github.com/llvm/llvm-project/pull/191004