llvm-project/clang/test/PCH/typo.m

// RUN: %clang_cc1 -x objective-c-header -emit-pch -o %t %S/Inputs/typo.h
// RUN: %clang_cc1 -include-pch %t -verify %s
// In header: expected-note{{declared here}}
void f() {
  [NSstring alloc]; // expected-error{{unknown receiver 'NSstring'; did you mean 'NSString'?}}
}
When performing typo correction, look through the set of known identifiers to determine good typo-correction candidates. Once we've identified those candidates, we perform name lookup on each of them and the consider the results. This optimization makes typo correction > 2x faster on a benchmark example using a single typo (NSstring) in a tiny file that includes Cocoa.h from a precompiled header, since we are deserializing far less information now during typo correction. There is a semantic change here, which is interesting. The presence of a similarly-named entity that is not visible can now affect typo correction. This is both good (you won't get weird corrections if the thing you wanted isn't in scope) and bad (you won't get good corrections if there is a similarly-named-but-completely-unrelated thing). Time will tell whether it was a good choice or not. llvm-svn: 116528 2010-10-15 06:11:03 +08:00			`// RUN: %clang_cc1 -x objective-c-header -emit-pch -o %t %S/Inputs/typo.h`
			`// RUN: %clang_cc1 -include-pch %t -verify %s`
			`// In header: expected-note{{declared here}}`
			`void f() {`
			`[NSstring alloc]; // expected-error{{unknown receiver 'NSstring'; did you mean 'NSString'?}}`
			`}`