Type annotations for instruction operands are omitted, e.g.
```
%3 = struct $S(%1, %2)
```
Operand types are redundant anyway and were only used for sanity checking in the SIL parser.
But: operand types _are_ printed if the definition of the operand value was not printed yet.
This happens:
* if the block with the definition appears after the block where the operand's instruction is located
* if a block or instruction is printed in isolation, e.g. in a debugger
The old behavior can be restored with `-Xllvm -sil-print-types`.
This option is added to many existing test files which check for operand types in their check-lines.
Today ParenType is used:
1. As the type of ParenExpr
2. As the payload type of an unlabeled single
associated value enum case (and the type of
ParenPattern).
3. As the type for an `(X)` TypeRepr
For 1, this leads to some odd behavior, e.g the
type of `(5.0 * 5).squareRoot()` is `(Double)`. For
2, we should be checking the arity of the enum case
constructor parameters and the presence of
ParenPattern respectively. Eventually we ought to
consider replacing Paren/TuplePattern with a
PatternList node, similar to ArgumentList.
3 is one case where it could be argued that there's
some utility in preserving the sugar of the type
that the user wrote. However it's really not clear
to me that this is particularly desirable since a
bunch of diagnostic logic is already stripping
ParenTypes. In cases where we care about how the
type was written in source, we really ought to be
consulting the TypeRepr.
There was a special case here to type-check `T.init` as a single closure
`{ args.. in T.init(args..) }`, but really, we can do that for any static
member applied to a static metatype base, including operators.
Also fix SILGen's function conversion peephole so it looks through
`as (T...) -> U` coercions that don't involve bridging.
Remove the preallocated closure discriminator from KeyPathExpr and go back
to expanding them using an AutoClosureExpr inside of a CaptureListExpr now
that that's supported. This allows the discriminator to be assigned during
type checking without disturbing the indexing of explicit closure literals.
Sometimes we emit a closure literal with escaping/nonthrowing/nonasync type
into a context that wants a nonescaping/throwing/async function, and it
ends up wrapped in a conversion. We can look through any of these and emit
the closure literal directly with those effects.
