This removes a bit of global state from the TypeChecker class, and
allows C function pointers to be formed to closures that capture
local functions, but have no transitive captures.
This calculates a result directly from the function's result type
instead of checking a bit that was previously set by the type
checker. Also, always returns true for constructors to simplify
some callers.
Current logic in `applySolutionFixes` didn't actually look inside
of single-expression closures (because of brace statement) or
closures which are transformed by function builders.
Resolves: rdar://problem/51167632
CSDiag could re-typecheck closure or other expression which has editor
placeholder inside allowing type variables be bound to unresolved
type, which doesn't really form a valid solution to be applied to AST.
So we need to guard against trying to transform placeholder into a call
to `_undefined` in such case, otherwise in asserts build it's going to
crash with an assert but in release build it would crash in some other
place e.g. xSILGen or trying to type-check captures.
Resolves: rdar://problem/48937223
Resolves: rdar://problem/51599529
If solution application is attempted for one of the sub-expressions,
while diagnostics are trying to narrow down where the failure is
located, don't record that captures need to be computed for closures,
because that could fail later on as in such conditions expressions
are not guaranteed to have correct types (e.g. some types could be
set to "unresolved").
When we perform constraint generation while solving, capture the
type mappings we generate as part of the solver scope and solutions,
rolling them back and replaying them as necessary. Otherwise, we’ll
end up with uses of stale type variables, expression/parameter/type-loc
types set twice, etc.
Fixes rdar://problem/50390449 and rdar://problem/50150314.
When calling a function whose parameter specifies a function builder
with a multi-statement closure argument, transform the closure into
a single expression via the function builder. Should the result
type checker, replace the closure body with the single expression.
The walker in SILGenLazyConformance.cpp should be sufficient to catch
any conformances needed at runtime, and after all the recent changes
SILGen is now able to trigger lazy conformance checking and synthesis
of fully-checked function bodies for accessors, which is enough to
remove the explicit conformance checks from Sema in this case.
When applying a solution to a nil literal of Optional type, we would
build a direct reference to Optional<T>.none instead of leaving the
NilLiteralExpr in place, because this would generate more efficient
SIL that avoided the call to the Optional(nilLiteral: ()) witness.
However, a few places in the type checker build type-checked AST, and
they build NilLiteralExpr directly. Moving the peephole to SILGen's
lowering of NilLiteralExpr allows us to simplify generated SIL even
further by eliding an unnecessary metatype value. Furthermore, it
allows SILGen to accept NilLiteralExprs that do not have a
ConcreteDeclRef set, which makes type-checked AST easier to build.
Instead of always requiring a call to be made to pass argument
to `@autoclosure` parameter, it should be allowed to pass argument
by value to `@autoclosure` parameter which can return a function
type.
```swift
func foo<T>(_ fn: @autoclosure () -> T) {}
func bar(_ fn: @autoclosure @escaping () -> Int) { foo(fn) }
```
THere is no longer any reason to complete ClangImporter-synthesized _ObjectiveCBridgeable
conformances in Sema. SILGen will determine the ones that it needs and will trigger
conformance checking as needed automatically.
