Handle `trim(generic)` in select type stmt

[jinangshah21]

MRE:

program select_type_char_mre
    implicit none

    call print_any("  Hello World  ")

contains

    subroutine print_any(generic)
        class(*), intent(in) :: generic
        select type (generic)
        type is (character(len=*))
            print *, trim(generic)
        end select
    end subroutine print_any

end program select_type_char_mre

LFortran Error:

ASR verify pass error: Unexpected args, StringTrim expects (char) as arguments
  --> d.f90:12:22
   |
12 |             print *, trim(generic)
   |                      ^^^^^^^^^^^^^ failed here

[Adityazzzzz]

@jinangshah21
I have been working on fixing this issue. I found that visit_SelectType was missing the logic to handle TypeStmtType correctly (it was defaulting to Class(*) instead of creating a shadow variable for Character).

I implemented the fix in ast_body_visitor.cpp to create a shadow variable inside the select type block. However, I am hitting a backend assertion in asr_to_llvm.cpp:

LCOMPILERS_ASSERT failed: src/libasr/codegen/asr_to_llvm.cpp
function setup_string_length(), line number 773
ERROR MESSAGE: Shouldn't define assumed length string variable (They're only arguments)
The Problem: The shadow variable we create for type is (character(len=*)) inherits the len=* property.

Since it is inside a block, it is treated as a Local Variable.

The LLVM backend refuses to allocate len=* variables on the stack unless they are Dummy Arguments (intent(in)).

What I tried:

Pointer Wrapper: I wrapped the shadow variable in ASR::make_Pointer_t. I expected this to work (since pointers have fixed size), but the backend still checks the underlying type's length and crashes.

Intent(In): I tried marking the shadow variable as Intent::In to mimic a dummy argument, but this causes other backend assertions because it's not actually in the function signature.

Question: How should we represent the shadow variable for type is (character(len=*)) in ASR?

Should asr_to_llvm.cpp be relaxed to allow len=* if the variable is a Pointer?

Or is there a specific way to set up the Associate node so the backend knows the storage comes from the selector?

Here is the diff of my current attempt in ast_body_visitor.cpp:

// Inside visit_SelectType case TypeStmtType:
// ...
selector_type = determine_type(...);

// I tried wrapping it in a pointer to avoid stack allocation of unknown length
selector_type = ASRUtils::make_Pointer_t_util(al, x.base.base.loc, selector_type);

// Creating the shadow variable
assoc_sym = ASR::down_cast<ASR::symbol_t>(ASRUtils::make_Variable_t_util(
    al, x.base.base.loc, current_scope, selector_variable->m_name, 
    ... ASR::intentType::Local ... 
));
current_scope->add_symbol(to_lower(std::string(selector_variable->m_name)), assoc_sym);

Any guidance on the correct ASR representation for this would be great!

[jinangshah21]

I think you don't need to add shadow variable for this. Try to bypass this error by checking current select type is block type.

[Adityazzzzz]

I tried to bypass error as instructed by you.
but everytime test results in this

LCOMPILERS_ASSERT failed: /home/adityazzzz/lfortran/src/libasr/../libasr/asr.h
function down_cast(), line number 40 at 
f != nullptr
Aborted (core dumped)

[jinangshah21]

Try to locate from where this error was coming and fix that