llvm-context: lazy handling of function arguments and immutable data (#282)

- Lazily load function arguments so that they can be passed as pointers.
- Lazily call the immutable store function to avoid storing zero sized
immutable data.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/solidity/src/yul/parser/statement/variable_declaration.rs

@@ -121,7 +121,7 @@ where
                                 .insert_constant(identifier.inner.clone(), constant);
                         }
 
-                        value.to_llvm()
+                        value.access(context)?
                     }
                     None => r#type.const_zero().as_basic_value_enum(),
                 }
@@ -175,7 +175,8 @@ where
                 .collect::<Vec<inkwell::types::BasicTypeEnum<'ctx>>>()
                 .as_slice(),
         );
-        if expression.value.get_type() != llvm_type.as_basic_type_enum() {
+        let value = expression.access(context)?;
+        if value.get_type() != llvm_type.as_basic_type_enum() {
             anyhow::bail!(
                 "{} Assignment to {:?} received an invalid number of arguments",
                 location,
@@ -183,7 +184,7 @@ where
             );
         }
         let pointer = context.build_alloca(llvm_type, "bindings_pointer");
-        context.build_store(pointer, expression.to_llvm())?;
+        context.build_store(pointer, value)?;
 
         for (index, binding) in self.bindings.into_iter().enumerate() {
             let pointer = context.build_gep(