Passing a VLA to a function from within another function using `VAR_IN_OUT`

[arhusebo]

Describe the bug Passing a VLA to a function from within another function using VAR_IN_OUT results in a compilation error. Not sure if this is intended behavior, but the example apparently compiles in at least one other IEC 61131-compliant environment.

To Reproduce

FUNCTION bar
	VAR_IN_OUT
		val : ARRAY[*] OF LREAL;
	END_VAR
END_FUNCTION

FUNCTION foo
	VAR_IN_OUT
		val : ARRAY[*] OF LREAL;
	END_VAR
	bar(val);
END_FUNCTION

Compiling yields error[E037]: Invalid assignment: cannot assign 'ARRAY[*] OF LREAL' to 'ARRAY[*] OF LREAL'.

Expected behavior Both functions should reference the same array.

[ghaith]

I'm assuming we should not do any check here, if we're going from 1 compatible vla to the other, we can just copy the fat pointer to the next function. The underlying array pointer would remain the same.

[mhasel]

This doesn't seem to be limited to VLAs. I can reproduce this with ARRAY[...] OF ARRAY[...] in a VAR_IN_OUT block:

FUNCTION arrayFn
    VAR_IN_OUT
        inOutArray: ARRAY[1..5] OF ARRAY[0..80] OF CHAR;
    END_VAR

    inOutArray[1][0] := 'V';
    inOutArray[1][1] := 'a';
    inOutArray[1][2] := 'l';
    inOutArray[1][3] := 'u';
    inOutArray[1][4] := 'e';
END_FUNCTION

FUNCTION main
    VAR
        localArray: ARRAY[1..5] OF ARRAY[0..80] OF CHAR;
    END_VAR

    arrayFn(inOutArray := localArray);
END_FUNCTION

error[E037]: Invalid assignment: cannot assign 'ARRAY[1..5] OF ARRAY[0..80] OF CHAR' to 'ARRAY[1..5] OF ARRAY[0..80] OF CHAR'
   ┌─ target/demo2.st:18:13
   │
18 │     arrayFn(inOutArray := localArray);
   │             ^^^^^^^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'ARRAY[1..5] OF ARRAY[0..80] OF CHAR' to 'ARRAY[1..5] OF ARRAY[0..80] OF CHAR'

Compilation aborted due to critical errors.
Hint: You can use `plc explain <ErrorCode>` for more information