Fixes SR-2757.
Variables in capture lists are treated as 'let' constants, which can
result in misleading, incorrect diagnostics. Mark them as such in order
to produce better diagnostics, by adding an extra parameter to the
VarDecl initializer.
Alternatively, these variables could be marked as implicit, but that
results in other diagnostic problems: capture list variables that are
never used produce warnings, but these warnings aren't normally emitted for
implicit variables. Other assertions in the compiler also misfire when
these variables are treated as implicit.
Another alternative would be to walk up the AST and determine whether
the `VarDecl`, but there doesn't appear to be a way to do so.
Specialize and improve the "downcast only unwraps optionals"
diagnostic to provide specific diagnostics + Fix-Its for the various
casts of forced cast, conditional cast, and "isa" check. Specifically:
* With a forced cast, customize the diagnostic. We still insert the
appropriate number of !'s, but now we remove the 'as! T' (if an
implicit conversion would suffice) or replace the 'as!' with 'as'
(if we still need a bridge)
* With a conditional cast, only emit a diagnostic if we're removing
just one level of optional. In such cases, we either have a no-op
(an implicit conversion would do) or we could just use 'as' to the
optional type, so emit a customized warning to do that. If we are
removing more than one level of optional, don't complain:
conditional casts can remove optionals. Add the appropriate Fix-Its
here.
* With an 'is' expression, only emit a diagnostic if we're removing
just one level of optional. In this case, the 'is' check is
equivalent to '!= nil'. Add a Fix-It for that.
Across the board, reduce the error to a warning. These are
semantically-well-formed casts, it's just that they could be written
better.
Fixes rdar://problem/28856049 and rdar://problem/22275685.
The type checker implements logic for handling checked casts in two
places: the constraint solver (for type-checking expressions
containing "as!" or "as?") and as a top-level entrypoint for
type-checking as?/as! for diagnostics and is/as patterns. Needless to
say, the two implementations were inconsistent, and in fact both were
wrong, leading to various problems---rejecting perfectly-valid "as!"
and "as?" casts outright, bogus warnings that particular as!/as? casts
always-succeed or always-fail when they wouldn't, and so on.
Start detangling the mess in two ways. First, drastically simplify the
handling of checked casts in the constraint solver, eliminating the
unprincipled "subtype" constraint checks that (among other things)
broke the handling of checked casts that involved bridging or optional
unwrapping. The simpler code is more permissive and more correct; it
essentially accepts that the user knows what she is doing with the
cast.
Second, make the type checker's checking of casts far more thorough,
which includes:
* When we're performing a collection cast, actually check that the
element types (and key types, for a dictionary) are castable, rather
than assuming all collection casts are legitimate. This means we'll
get more useful "always fails" and "always succeeds" diagnostics for
array/set/dictionary.
* Handle casts from a bridged value type to a subclass of the
corresponding bridged class type. Previously, these would be
incorrectly classified as "always fails".
While I'm here, eliminate a spurious diagnostic that occurs when using
a conditional cast ("as?") that could have been a coercion/bridging
conversion ("as"). The optional injection we synthesize to get the
resulting type correct was getting diagnosed as an implicit coercion,
but shouldn't have been.
Previously, bridging conversions were handled as a form of "explicit
conversion" that was treated along the same path as normal
conversions in matchTypes(). Historically, this made some
sense---bridging was just another form of conversion---however, Swift
now separates out bridging into a different kind of conversion that is
available only via an explicit "as". This change accomplishes a few
things:
* Improves type inference around "as" coercions. We were incorrectly
inferring type variables of the "x" in "x as T" in cases where a
bridging conversion was expected, which cause some type inference
failures (e.g., the SR-3319 regression).
* Detangles checking for bridging conversions from other conversions,
so it's easier to isolate when we're applying a bridging
conversion.
* Explicitly handle optionals when dealing with bridging conversions,
addressing a number of problems with incorrect diagnostics, e.g.,
complains about "unrelated type" cast failures that would succeed at
runtime.
Addresses rdar://problem/29496775 / SR-3319 / SR-2365.
- TypeAliasDecl::getAliasType() is gone. Now, getDeclaredInterfaceType()
always returns the NameAliasType.
- NameAliasTypes now always desugar to the underlying type as an
interface type.
- The NameAliasType of a generic type alias no longer desugars to an
UnboundGenericType; call TypeAliasDecl::getUnboundGenericType() if you
want that.
- The "lazy mapTypeOutOfContext()" hack for deserialized TypeAliasDecls
is gone.
- The process of constructing a synthesized TypeAliasDecl is much simpler
now; instead of calling computeType(), setInterfaceType() and then
setting the recursive properties in the right order, just call
setUnderlyingType(), passing it either an interface type or a
contextual type.
In particular, many places weren't setting the recursive properties,
such as the ClangImporter and deserialization. This meant that queries
such as hasArchetype() or hasTypeParameter() would return incorrect
results on NameAliasTypes, which caused various subtle problems.
- Finally, add some more tests for generic typealiases, most of which
fail because they're still pretty broken.
This reverts commit e172383e2f.
There were two problems with this commit:
- This was a source-breaking change and should have been feature-gated.
- It only addressed one narrow case of SE-0110.
Fixes <rdar://problem/28621719>.
Previously, getInterfaceType() would return getType() if no
interface type was set. Instead, always set an interface type
explicitly.
Eventually we want to remove getType() altogether, and this
brings us one step closer to this goal.
Note that ParamDecls are excempt from this treatment, because
they don't have a proper interface type yet. Cleaning this up
requires more effort.
Previously, getInterfaceType() would return getType() if no
interface type was set. Instead, always set an interface type
explicitly.
Eventually we want to remove getType() altogether, and this
brings us one step closer to this goal.
Note that ParamDecls are excempt from this treatment, because
they don't have a proper interface type yet. Cleaning this up
requires more effort.
In usesTypeMetadataOfFormalType(), bail out if we're checking a cast and
the casted-to type is null or error_type. We would have already emitted
a diagnostic on the function body by this point and this avoids crashing
immediately after.
Suggestions on a better place for the test would be welcome. The crash
requires the cast to be in the body of a function in an NSObject-derived
cast.
Resolves rdar://problem/28583595.
If we found any error in a list, in most cases, we cannot expect that the
following tokens could construct a valid element. Skip them, instead of trying
to parse them as the next element. This significally reduces bogus diagnostics.
Bailout if seeing tok::eof or token that can never start a element, after
parsing an element. This silences superfluous "expected ',' separator" error,
or misleading expected declaration error. What we should emit is
"expected ')' in expression list, or "expected '}' in struct".
This fixes a usability regression with the removal of @noreturn
in Swift 3. Previously, it was legal to write this:
let callback: () -> Int = { fatalError() }
Now that the special @noreturn attribute has been replaced with
a Never type, the above fails to typecheck, because the expression
now has type 'Never', and we expect a value of type 'Int'.
Getting around this behavior requires ugly workarounds to force the
parser to treat the body as a statement rather than an expression;
for example,
let callback: () -> Int = { _ = (); fatalError() }
This patch generalized single-expression closures to allow
the 'Never to T' conversion. Note that this is rather narrow
in scope -- it only applies to closure *literals*, single-expression
ones at that, not arbitrary function *values*.
In fact, it is not really a conversion at all, but more of a
desugaring rule for single-expression closures. They can now be
summarized as follows:
- If the closure literal has contextual return type T and
the expression has Never type, the closure desugars as
{ _ = <expr> }, with no ReturnStmt.
- If the closure literal has contextual return type T for some
non-void type T, the closure desugars as { return <expr> };
the expression type must be convertible to T.
- If the closure literal has contextual return type Void, and
the expression has some non-Void type T, the closure
desugars as { _ = <expr>; return () }.
Fixes <rdar://problem/28269358> and <https://bugs.swift.org/browse/SR-2661>.
From the Swift documentation:
"If you define an optional variable without providing a default value,
the variable is automatically set to nil for you."
This was causing us to emit diagnostics talking about τ_m_n, which is
not helpful.
Now that generic function types print sanely, print them in a few
places where we were previously printing PolymorphicFunctionTypes.
(by making it a normal argument with a label and not a trailing
closure)
Diagnostic part of rdar://problem/25607552. A later commit will keep
us from getting in this situation quite so much when default arguments
are involved.
Until the point where ASTScope-based unqualified name lookup is the
default, unqualified name lookup can still find names declared *after*
the source location. The 'hasType' check no longer makes sense, so actually
check the source location of the entity we found.
This commit built upon the work of Pull Request 3895. Apart from the
work to make the following work
```swift
let f: (Int, Int) -> Void = { x in } // this is now an error
```
This patch also implement the part 2 mentioned in the #3895
```swift
let g: ((Int, Int)) -> Void = { y in } // y should have type (Int, Int)
```
Suggest a fix-it for unqualified references to all static members
from instance context, not just enum elements.
Also, fix a small problem with the fix-it for replacing protocol
names with 'Self' inside extension bodies -- we didn't handle nested
functions properly.
We do this in a more general way higher up in the constraint
solver. Filtering out methods in name lookup only hurts
diagnostics.
In fact I don't think this behavior was intentional at all,
since the code in question was originally written in 2013
before a lot of the more recent member lookup and diagnostic
code was added.
This does break source compatibility though, but in a minor
way. See the change to the CoreGraphics overlay. Again,
though, I think this was an accident and not intentional.
