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.
Before the update to support the new syntax, the decl checker treated private and fileprivate members of objcImpl extensions as non-@objc by default. But SE-0436 specified that private and fileprivate members should be implicitly @objc unless opted out, so when support for the final syntax was added, this behavior was changed retroactively.
Unfortunately, we’ve found that some early adopters depended on the old behavior. Restore some logic deleted by #73309 for early adopter syntax *only*, with a warning telling the developer to put `final` or `@nonobjc` on the declaration if they want to preserve the behavior after updating it.
Also tweaks the ObjCImplementationChecker to ensure this logic will actually be run in time for it to suppress the “upgrade to @objc @implementation” warning, and corrects a couple of regressions arising from that change.
Fixes rdar://135747897.
Previous changes have made it so that `private let`s in an objcImpl extension are implicitly `@objc`, which changed downstream behavior in a SILOptimizer test. The new behavior is actually more correct, so codify this behavior change by modifying the test.
It lowers let property accesses of classes.
Lowering consists of two tasks:
* In class initializers, insert `end_init_let_ref` instructions at places where all let-fields are initialized.
This strictly separates the life-range of the class into a region where let fields are still written during
initialization and a region where let fields are truly immutable.
* Add the `[immutable]` flag to all `ref_element_addr` instructions (for let-fields) which are in the "immutable"
region. This includes the region after an inserted `end_init_let_ref` in an class initializer, but also all
let-field accesses in other functions than the initializer and the destructor.
This pass should run after DefiniteInitialization but before RawSILInstLowering (because it relies on `mark_uninitialized` still present in the class initializer).
Note that it's not mandatory to run this pass. If it doesn't run, SIL is still correct.
Simplified example (after lowering):
bb0(%0 : @owned C): // = self of the class initializer
%1 = mark_uninitialized %0
%2 = ref_element_addr %1, #C.l // a let-field
store %init_value to %2
%3 = end_init_let_ref %1 // inserted by lowering
%4 = ref_element_addr [immutable] %3, #C.l // set to immutable by lowering
%5 = load %4
