While we work out the remaining performance improvements in the type checker, we can improve the user experience for some "runaway solver" bugs by setting a limit on the amount of temporary memory allocated for type variables when solving over a single expression.
Exponential behavior usually manifests itself while recursively attempting bindings over opened type variables in an expression. Each one of these bindings may result in one or more fresh type variables being created. On average, memory consumption by type variables is fairly light, but in some exponential cases it can quickly grow to many hundreds of megabytes or even gigabytes. (This memory is managed by a distinct arena in the AST context, so it's easy to track.) This problem is the source of many of the "freezing" compiler and SourceKit bugs we've been seeing.
These changes set a limit on the amount of memory that can be allocated for type variables while solving for a single expression. If the memory threshold is exceeded, we can surface a type error and suggest that the user decompose the expression into distinct, less-complex sub-expressions.
I've set the current threshold to 15MB which, experimentally, avoids false positives but doesn't let things carry on so long that the user feels compelled to kill the process before they can see an error message. (As a point of comparison, the largest allocation of type variable data while solving for a single expression in the standard library is 592,472 bytes.) I've also added a new hidden front-end flag, "solver-memory-threshold", that will allow users to set their own limit, in bytes.
Swift SVN r20986
Previously, we only retained the module in which a normal protocol
conformance occurred, which meant we either had to go searching for
the appropriate extension (yuck) or do without that information. This
is part of the separating-extension-archetypes work.
Swift SVN r20793
Expose Substitution's archetype, replacement, and conformances only through getters so we can actually assert invariants about them. To start, require replacement types to be materializable in order to catch cases where the type-checker tries to bind type variables to lvalue or inout types, and require the conformance array to match the number of protocol conformances required by the archetype. This exposes some latent bugs in the test suite I've marked as failures for now:
- test/Constraints/overload.swift was quietly suffering from <rdar://problem/17507421>, but we didn't notice because we never tried to codegen it.
- test/SIL/Parser/array_roundtrip.swift doesn't correctly roundtrip substitutions, which I filed as <rdar://problem/17781140>.
Swift SVN r20418
As a first step toward addressing <rdar://problem/17507421>, introduce a type property we can use as a more general replacement for is<LValueType> that also catches tuples of @lvalues (and in the future, potential (@lvalue T)? optional-of-lvalue formations) and other types that need to be loaded in non-assignment contexts.
Swift SVN r20371
Add a set of _preconditionOptionalHasValue intrinsics that merely test that an optional has a case. Emit an lvalue ForceValueExpr as a physical lvalue, first asserting the precondition then projecting out the Some payload.
Swift SVN r20188
Introduce the new BooleanLiteralConvertible protocol for Boolean
literals. Take "true" and "false" as real keywords (which is most of the
reason for the testsuite churn). Make Bool BooleanLiteralConvertible
and the default Boolean literal type, and ObjCBool
BooleanLiteralConvertible. Fixes <rdar://problem/17405310> and the
recent regression that made ObjCBool not work with true/false.
Swift SVN r19728
This always wrapped a single GenericTypeParamDecl *, and provided no benefit
over just using the decl directly.
No (intended) functionality change.
Swift SVN r19628
Previously, bridged value types and their corresponding Objective-C
classes allow inter-conversion via a number of user-defined conversion
functions in the Foundation module. Instead, make this a general
feature of the type checker so we can reason about it more
directly. Fixes <rdar://problem/16956098> and
<rdar://problem/17134986>, and eliminates 11 (half) of the
__conversion functions from the standard library and overlays.
A few notes:
- The XCTest changes are because a String can no longer directly
conform to CVarArg: this is a Good Thing (TM), because it should be
ambiguous: did you mean to pass it as an NSString or a C string?
- The Objective-C representations for the bridged collections are
hard-coded in the type checker. This is unfortunate and can be
remedied by adding another associated type to the
_BridgedToObjectiveC protocol.
Swift SVN r19618
These types are needed by enough of the stack now that it makes sense to centralize their lookup and caching onto the AST context like other core types.
Swift SVN r19029
not a struct wrapping an Optional.
Among other things, this means you can now pattern-match on
an IUO. It also makes it more convenient to build and destroy
them.
SILGen's type lowering should probably canonicalize one kind
of optional to the other so that we don't get silly abstraction
costs from conversion.
Swift SVN r18991
s/_dictionaryCheckedDownCast/_dictionaryDownCastConditional/g
s/_dictionaryBridgeFromObjectiveC/_dictionaryBridgeFromObjectiveCConditional/g
Swift SVN r18931
This is all goodness, and eliminates a major source of implicit conversions.
One thing this regresses on though, is that we now reject "x == nil" where
x is an option type and the element of the optional is not Equtatable. If
this is important, there are ways to enable this, but directly testing it as
a logic value is more straight-forward.
This does not include support for pattern matching against nil, that will be
a follow on patch.
Swift SVN r18918
This is better than requiring people to go through Ctx.getModule() using
Ctx.StdlibModuleName. There aren't that many cases of this, but they
shouldn't be using a completely different API.
The default behavior remains the same: if the standard library has not been
loaded, null will be returned.
Refinement of r18796, which modified the behavior of SourceFiles to assume
that the standard library had already been loaded.
Swift SVN r18813
This performs very conservative dependency generation for each compile task
within a full compilation. Any source file, swiftmodule, or Objective-C
header file that is /touched/ gets added to the dependencies list, which
is written out on a per-input basis at the end of compilation.
This does /not/ handle dependencies for the aggregated swiftmodule, swiftdoc,
generated header, or linked binary. This is just the minimum needed to get
Xcode to recognize what needs to be rebuilt when a header or Swift source
file changes. We can revisit this later.
This finishes <rdar://problem/14899639> for now.
Swift SVN r18045
- Continue adding support for checked downcasts of array types (rdar://problem/16535104)
- Fix non-bridged array conversions post-r17868
- Fix rdar://problem/16773693
- Add tests for NSArray coercions to and from Array<T>
Swift SVN r17957
Introduce some infrastructure that allows us to speculatively apply
localized fixes to expressions during constraint solving to fix minor
typos and omissions. At present, we're able to introduce the fixes
during constraint simplification, prefer systems with fewer fixes when
there are multiple fixes, and diagnose the fixes with Fix-Its.
Actually rewriting the AST to reflect what the Fix-Its are doing is
still not handled.
As a start, introduce a fix that adds '()' if it appears to have been
forgotton, producing a diagnostic like this if it works out:
t.swift:8:3: error: function produces expected type 'B'; did you mean
to call it with '()'?
f(g)
^
()
Note that we did regress in one test case
(test/NameBinding/multi-file.swift), because that diagnostic was
getting lucky with the previous formulation.
Swift SVN r16937
Also, create the Clang module loader directly rather than indirecting through
a "get constructor" function. It's no longer a valid configuration to not
have a Clang importer.
Swift SVN r16862
This was part of the original weak design that
there was never any particular reason to rush the
implementation for. It's convenient to do this now
so that we can use it to implement Unmanaged<T> for
importing CF types.
Swift SVN r16693
