Fix a few bugs where we would fail to properly determine header to
module correspondence when determining whether to suggest a #include or
import, and suggest a #include more often in language modes where there
is no import syntax. Generally, if the target is in a header with
include guards or #pragma once, we should suggest either #including or
importing that header, and not importing a module that happens to
textually include it.
In passing, improve the notes we attach to the corresponding
diagnostics: calling an entity that we couldn't see "previous" is
confusing.
Summary:
Otherwise the definition (first found) for ObjCInterfaceDecl's might
precede the module one, which will eventually lead to crash, since
diagnoseMissingImport needs one coming from a module.
This behavior changed after Richard's r342018, which started to look
into the definition of ObjCInterfaceDecls.
rdar://problem/49237144
Reviewers: rsmith, arphaman
Subscribers: jkorous, dexonsmith, ributzka, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D66982
llvm-svn: 372039
Richard Smith