Type of folded constant expression can be ambiguous for user types

[trocher]

Version Information

• vyper Version (output of vyper --version): 0.3.8+commit.d76c6ed2
• OS: OSX
• Python Version (output of python --version): 3.8.0

What's your issue about?

The type of folded constant expression can be ambiguous when it cannot be inferred prior to typeching. This leads the constant expression to mostly act as a macro.

vyper/vyper/ast/folding.py

Lines 183 to 189 in 187ab0e

	try:
	type_ = type_from_annotation(node.annotation)
	except UnknownType:
	# handle user-defined types e.g. structs - it's OK to not
	# propagate the type annotation here because user-defined
	# types can be unambiguously inferred at typechecking time
	pass

For example, the following code compiles while I don't think it should.

struct A:
    a:uint256

b: constant(DynArray[A,1]) = []

@external
def test():
    a:DynArray[uint256,1] = b

How can it be fixed?

I'm not really sure how this could be fixed easily with the current folding design.

[trocher]

The issue is no longer there in 4b4e188, the example above fails compilation. Was removed by the refactoring of folding (#3719, #3669)