Calling `getInnermostDeclContext()->getParentSourceFile()` on a macro-produced decl does not seem to be a reliable way to obtain the macro expansion source file, because `PatternBindingDecl` is not a `DeclContext` and `getInnermostDeclContext()` falls back outside the macro expansion file. This patch switches to using `getSourceFileContainingLocation` when possible.
Resolves rdar://109376568.