This fixes the problem in JVM IR backend which didn't pass bound
receiver value of an adapted function reference to the superclass
(kotlin/jvm/internal/AdaptedFunctionReference), which caused equals to
work incorrectly on such references (see changes in box tests).
Previously, bound adapted function reference was represented as
IrFunctionExpression to an adapter function which calls the callee. The
value of the bound receiver in that case could only be found in the body
of that adapter function. This is not very convenient, so this change
makes psi2ir produce a block of the adapter function + reference to it.
The bound receiver value is then found in the reference. This is
basically similar to what ProvisionalFunctionExpressionLowering is doing
for all function expressions. And since this IR structure is already
supported in FunctionReferenceLowering, the problem in the JVM IR is
fixed without any additional modifications.
However, inliners do not support this IR structure yet, see KT-38535 and
KT-38536.
It's used as a superclass for anonymous classes for adapted function
references. Its main feature is that it _doesn't_ inherit from KFunction
(as opposed to FunctionReference), as per the decision to postpone
reflection support for adapted function references in KT-36024.
#KT-36024 Fixed
Function references are now equal if they refer to the same function,
and if the parameter/return type adaptation, which happens when a
reference is used where some function type is expected, is exactly the
same. This includes the number of expected positional parameters (which
can be affected by defaults/varargs), whether the coercion of vararg
parameter to Array type happened, and whether the coercion of return
type to Unit happened.
#KT-37543 Fixed
Vitaly