Only return macros that are valid in their current position, ie. an
attached macro is not valid on a nominal.
Also return freestanding expression macros in code block item position
and handle the new freestanding code item macros.
Resolves rdar://105563583.
We don't need special completion logic for things like `#file` and
`#line` now that they are declared in the standard library. Drop it
and update tests.
Align the grammar of macro declarations with SE-0382, so that macro
definitions are parsed as an expression. External macro definitions
are referenced via a referenced to the macro `#externalMacro`. Define
that macro in the standard library, and recognize uses of it as the
definition of other macros to use externally-defined macros. For
example, this means that the "stringify" macro used in a lot of
examples is now defined as something like this:
@expression macro stringify<T>(_ value: T) -> (T, String) =
#externalMacro(module: "MyMacros", type: "StringifyMacro")
We still parse the old "A.B" syntax for two reasons. First, it's
helpful to anyone who has existing code using the prior syntax, so they
get a warning + Fix-It to rewrite to the new syntax. Second, we use it
to define builtin macros like `externalMacro` itself, which looks like this:
@expression
public macro externalMacro<T>(module: String, type: String) -> T =
Builtin.ExternalMacro
This uses the same virtual `Builtin` module as other library builtins,
and we can expand it to handle other builtin macro implementations
(such as #line) over time.
I think that preferring identical over convertible makes sense in e.g. C++ where we have implicit user-defined type conversions but since we don’t have them in Swift, I think the distinction doesn’t make too much sense, because if we have a `func foo(x: Int?)`, want don’t really want to prioritize variables of type `Int?` over `Int` Similarly if we have `func foo(x: View)`, we don’t want to prioritize a variable of type `View` over e.g. `Text`.
rdar://91349364
The meaning of EnableConcisePoundFile is going to shift slightly, so it makes sense to always include #filePath in completions. Also, @rintaro confirmed that this should be using KeywordKind::pound_filePath, not KeywordKind::pound_file.
