[clang] [clang-tools-extra] [clang][AST] Fix source range of class template implicit instantiations. (PR #156011)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

> The most important part for me, is that if `TagDecl::isThisDeclarationADefinition()` returns true, then I need `getSourceRange()` to return the content of the definition.

That's a more interesting limited part of the problem.

It seems strange to me that we produce a template instantiation which is a complete definition, but we somehow think the pattern used to produce it is a non-defining declaration. Maybe we could fix that instead?



https://github.com/llvm/llvm-project/pull/156011