This saves us from needing to re-match args to params in CSApply and is also
useful for a forthcoming change migrating code completion in argument position
to use the solver-based typeCheckForCodeCompletion api.
rdar://76581093
If have a function that takes a trailing closure as follows
```
func sort(callback: (_ left: Int, _ right: Int) -> Bool) {}
```
completing a call to `sort` and expanding the trailing closure results in
```
sort { <#Int#>, <#Int#> in
<#code#>
}
```
We should be doing a better job here and defaulting the trailing closure's to the internal names specified in the function signature. I.e. the final result should be
```
sort { left, right in
<#code#>
}
```
This commit does exactly that.
Firstly, it keeps track of the closure's internal names (as specified in the declaration of `sort`) in the closure's type through a new `InternalLabel` property in `AnyFunctionType::Param`. Once the type containing the parameter gets canonicalized, the internal label is dropped.
Secondly, it adds a new option to `ASTPrinter` to always try and print parameter labels. With this option set to true, it will always print external paramter labels and, if they are present, print the internal parameter label as `_ <internalLabel>`.
Finally, we can use this new printing mode to print the trailing closure’s type as
```
<#T##callback: (Int, Int) -> Bool##(_ left: Int, _ right: Int) -> Bool#>
```
This is already correctly expanded by code-expand to the desired result. I also added a test case for that behaviour.
If closure parameter has an explicit type, type resolution
would diagnose the issue and cache the resulting error type for
future use. Invalid types currently fail constraint generation,
which doesn't play well with result builders because constraint
generation for their bodies happens during solving.
Let's handle invalid parameters gracefully, replace them with
placeholders and let constraint generation proceed.
Resolves: rdar://75409111
Type inside of an editor placeholder is more of a hint than anything else,
so if it's incorrect let's diagnose that and use type variable instead to
allow solver to make forward progress.
Resolves: SR-14213
Resolves: rdar://74356736
If argument is a floating-point literal, with newly introduced implicit
Double<->CGFloat conversion, sometimes it's better to choose a concrete
function/operator overload on `CGFloat` even if it's not a default literal
type e.g. `let _: CGFloat = min(1.0, log(<CGFloat value>))` shouldn't form
solutions with `Double` arguments since it would result in multiple
implicit conversions, it's better to use a `CGFloat` type for the arguments.
While it is very convenient to default the ExtInfo state when creating
new function types, it also make the intent unclear to those looking to
extend ExtInfo state. For example, did a given call site intend to have
the default ExtInfo state or does it just happen to work? This matters a
lot because function types are regularly unpacked and rebuilt and it's
really easy to accidentally drop ExtInfo state.
By changing the ExtInfo state to an optional, we can track when it is
actually needed.
when it has property wrapper parameters.
The property wrapper type will be replaced with either the wrapped-value
or projected-value type, depending on the argument label/parameter name,
and CSApply will build a thunk to construct the property wrapper and call
the function.
property wrapper custom attribute to get the backing wrapper type
in CSApply.
This is necessary because implicit custom attributes do not have
TypeReprs, but they always have TypeExprs.
Move markAcceptableDiscardExprs into PreCheckExpr so that we can perform this analysis before we convert expressions like `_? = <value>` into `_ = <value>` since `_?` is now an expression with meaning, and we only want to perform this transformation when `_?` is on the LHS of an assignment
Rename `openUnboundGenericTypes` to `convertInferableTypes`. In addition to unbound generics, this method also converts placeholder types to fresh type variables.
