If a tuple is passed as the only argument to a function that takes two unnamed arguments, we try to diagnose the missing argument label. However, in the old diagnose code we didn’t distinguish between non-existing arguments and arguments without labels; both behaved the same.
Thus, the missing second argument in the function call would line up with the empty second argument label, not producing a diagnostic, but hitting an assertion later on.
Distinguish between the two to fix the issue.
Fixes rdar://64319340
Current logic fix-it didn't account for the first argument being re-ordered.
The start position for the first argument should always be the next token
after left paren denoting a start of the argument list.
Resolves: rdar://problem/70764991
The change to the forward-scanning rule regressed some diagnostics,
because we no longer generated the special "trailing closure mismatch"
diagnostic. Reinstate the special-case "trailing closure mismatch"
diagnostic, but this time do so as part of the normal argument
mismatch diagnostics so it is based on type information.
While here, clean up the handling of missing-argument diagnostics to
deal with (multiple) trailing closures properly, so that we can (e.g)
suggest adding a new labeled trailing closure at the end, rather than
producing nonsensical Fix-Its.
And, note that SR-12291 is broken (again) by the forward-scan matching
rules.
To preserve subtype relationship between element types of a collection
passed as an argument to a parameter represented by another collection
type let's extend opening of the collection types to be done for arguments
to @autoclosure parameters as well because implicit closure is transparent
to the caller.
Resolves: [SR-13135](https://bugs.swift.org/browse/SR-13135)
Resolves: rdar://problem/65088975
