`StructValue::get_fields` misbehaves for `zeroinitializer`, it should be using the type's info, not the operand count

[programmerjake]

Describe the Bug
StructValue doesn't correctly handle zeroinitializer, and wrongly returns no fields when using the field accessor functions (get_fields and friends), however if you use LLVMGetAggregateElement and the field count from the type, it works correctly.

To Reproduce
src/main.rs:

use inkwell::{
    context::Context,
    llvm_sys::core::LLVMGetAggregateElement,
    values::{AsValueRef, BasicValueEnum},
};

fn main() {
    let context = Context::create();
    let i8_ty = context.i8_type();
    let i16_ty = context.i16_type();
    let i8_i16_ty = context.struct_type(&[i8_ty.into(), i16_ty.into()], false);
    let ty = context.struct_type(&[i8_i16_ty.into(), i8_ty.into(), i16_ty.into()], false);
    let v = dbg!(ty.const_zero());
    dbg!(v.get_fields().collect::<Vec<_>>());
    unsafe {
        for i in 0..ty.count_fields() {
            let field = BasicValueEnum::new(LLVMGetAggregateElement(v.as_value_ref(), i));
            dbg!(field);
        }
    }
}

Cargo.toml:

[package]
name = "inkwell_bug"
version = "0.1.0"
edition = "2024"

[dependencies]
inkwell = { version = "0.10.0", features = ["no-libffi-linking", "llvm22-1", "target-powerpc", "llvm22-1-prefer-dynamic"], default-features = false }

Output I get:

[src/main.rs:13:13] ty.const_zero() = StructValue {
    struct_value: Value {
        name: "",
        address: 0x0000565064d09e80,
        is_const: true,
        is_null: true,
        is_undef: false,
        llvm_value: "{ { i8, i16 }, i8, i16 } zeroinitializer",
        llvm_type: "{ { i8, i16 }, i8, i16 }",
    },
}
[src/main.rs:14:5] v.get_fields().collect::<Vec<_>>() = []
[src/main.rs:18:13] field = StructValue(
    StructValue {
        struct_value: Value {
            name: "",
            address: 0x0000565064d0b1b0,
            is_const: true,
            is_null: true,
            is_undef: false,
            llvm_value: "{ i8, i16 } zeroinitializer",
            llvm_type: "{ i8, i16 }",
        },
    },
)
[src/main.rs:18:13] field = IntValue(
    IntValue {
        int_value: Value {
            name: "",
            address: 0x0000565064d0b1d0,
            is_const: true,
            is_null: true,
            is_undef: false,
            llvm_value: "i8 0",
            llvm_type: "i8",
        },
    },
)
[src/main.rs:18:13] field = IntValue(
    IntValue {
        int_value: Value {
            name: "",
            address: 0x0000565064d0b0c0,
            is_const: true,
            is_null: true,
            is_undef: false,
            llvm_value: "i16 0",
            llvm_type: "i16",
        },
    },
)

Expected Behavior
In the collect line, output three fields with value { i8, i16 } zeroinitializer, i8 0, and i16 0.

LLVM Version (please complete the following information):

• LLVM Version: 22.1.8 (from apt.llvm.org)
• Inkwell Branch Used: llvm22-1

Desktop (please complete the following information):

• OS: Debian 13

Additional Context
AFAICT rather than assuming a constant struct has operands, you should be using the type's field count and LLVMGetAggregateElement

[TheDan64]

Good catch, would accept a fix with tests