This is important for IR lowerings like PolymorphicSignatureLowering
which are very sensitive about the correct types of expressions and
placement of coercions to Unit (KT-59218).
A boolean parameter to `insertImplicitCasts` is not the best solution to
ensure that coercion to Unit is added. The best solution would be to fix
the TODO and generate coercion to the block's type for the last
statement. But that will affect many other places and will need to be
done separately => KT-59781.
Code in IrInterpreter is uncommented to fix the FIR test
`compiler/testData/ir/interpreter/exceptions/tryFinally.kt`; otherwise
evaluation of the function `returnTryFinally` there crashes with
"NoSuchElementException: ArrayDeque is empty". No idea why this test
didn't fail for K1 though, since the created IR is exactly the same.
For some unknown reason this breaks WASM backend with K2, but not with
K1 => KT-59800.
Simplify ifs when branches have condition true/false.
Simplify blocks containing only a variable declaration
and a variable get of the same variable. Simplify to
just the condition.
Do not introduce temporary variables for constants for
null checks. Constants have no side-effects and can be
reloaded freely instead of going through a local.
This simplifies code such as "42.toLong()!!" so that the
resulting code has no branches and uses no locals. The
simplifications happen as follows:
```
block
temp = 42.toLong()
when
(temp == null) throw NPE
(true) load temp
---> null test simplification
block
temp = 42.toLong()
when
(false) throw NPE
(true) load temp
---> when simplification
block
temp = 42.toLong()
load temp
---> block simplification
42.toLong()
```
Artem Kobzar