Make sure we canonicalize the original type for an ErrorType to ensure
that diagnostic logic can coalesce ErrorTypes that have the same
canonical type.
Move the logic from `FailureDiagnostic::resolveType` into
`Solution::simplifyType` to allow completion to use it too. While
here, also handle cases where the placeholder is from a different
member of the equivalence class to the generic parameter.
We accepted unnamed closure parameters if the type was an array literal, dictionary literal, tuple or function (because the `[` or `(` starting the type was sufficient to disambiguate the type from the parameter’s name). This was never an accepted syntax and we should disallow it.
If tuple doesn't have a label for its first element
and parameter does, let's assume parameter's label
to aid argument matching. For example:
```swift
func test(val: Int, _: String) {}
test(val: (42, "")) // expands into `(val: 42, "")`
```
Resolves: rdar://106775969
Tweaked usable check:
* Local type/func decls are usable even before declaration
* Outer nominal Instance member are not usable
* Type context cannot close over values in outer type contexts
Added shadowing rule by the base name:
* Type members don't shadow each other as long as they are in the
same type context.
* Local values shadow everything in outer scope
* Except that 'func' decl doesn't shadow 'var' decl if they are in the
same scope.
rdar://86285396
When there is a conversion from e.g. `(A) -> Void` to `(B) -> Void`
matching between `A` and `B` is going to have a special locator which
doesn't end in `TupleElement`, so `repairFailures` has to account
for that and fix it just like regular argument mismatch.
Resolves: rdar://problem/59066040
Since `simplifyRestrictedConstraintImpl` has both parent types and
does nested type matching it's a good place to diagnose top-level
contextual problems like mismatches in underlying types of optionals.
If parameter type is optional let's ignore that since argument could
be either optional itself or be injected into optional implicitly.
```swift
func foo(_: ((Int, Int) -> Void)!) {}
foo { _ in } // Missing second closure parameter
```
Originally type mismatches associated with conversions between
function types were only covered for coercions and assignments
but fix coverage grew since then and now it makes sense
to remove special case and let `repairFailures` take care of it.
When SE-110 was being implemented, we accidentally began to accept
closure parameter declarations that had no associated parameter names,
e.g.
foo { ([Int]) in /**/ }
This syntax has never been sanctioned by any version of Swift and should
be banned. However, the change was made long enough ago and there are
enough clients relying on this, that we cannot accept the source break
at the moment. For now, add a bit to ParamDecl that marks a parameter
as destructured, and back out setting the invalid bit on the type repr
for these kinds of declarations.
To prevent further spread of this syntax, stub in a warning that offers
to insert an anonymous parameter.
Resolves part of rdar://56673657 and improves QoI for errors like
rdar://56911630
Use the isInvalid() bit on the TypeRepr to signal that a closure
parameter is potentially a tuple destructure. This has two benefits
1) Parse is no longer using the isInvalid() bit on Decl
2) Invalidating the type repr itself means that we no longer spuriously
diagnose variable patterns in destructures as missing types.
In situations like this:
```swift
func foo(x: (Int, Int) {}
foo(x: 0, 0)
```
Left paren to form a missing tuple should be placed after
the label because belongs to the parameter and not the tuple.
Currently single parameter tuple splat fix/diagnostic supports only
cases where parameter is a concrete tuple type, let's enhance that to
support generic parameters as well e.g.:
```swift
func foo<T>(_: T) {}
foo(0, 1, 2) // `T` expects arguments to form a tuple e.g. `foo((0, 1, 2))`
```
If the only difference between two functions is `throws` and it
is not a subtype relationship, let's repair the problem by dropping
`throws` attribute and letting solver continue to search for
a solution, which would later be diagnosed.
Diagnose situation when a single "tuple" parameter is given N arguments e.g.
```swift
func foo<T>(_ x: (T, Bool)) {}
foo(1, false) // foo exptects a single argument of tuple type `(1, false)`
```
Escapingness is a property of the type of a value, not a property of a function
parameter. Having it as a separate parameter flag just meant one more piece of
state that could get out of sync and cause weird problems.
Instead, always look at the noescape bit in a function type as the canonical
source of truth.
This does mean that '@escaping' is now printed in a few diagnostics where it was
not printed before; we can investigate these as separate issues, but it is
correct to print it there because the function types in question are, in fact,
escaping.
Fixes <https://bugs.swift.org/browse/SR-10256>, <rdar://problem/49522774>.
