initializer & field location info missing in Error message

[MahadMuhammad]

Improving Error Constructor is missing fields - E0063

• Fixing this issue, help [E0063] constructor is missing fields #2387 to emit more user friendly error code and error emission similiar to rustc.
• You can view the same on compiler-explorer

---

I tried this code from E0063:

// https://doc.rust-lang.org/error_codes/E0063.html
struct Foo {
    x: i32,
    y: i32,
    z: i32,
}

fn main() {
    let x = Foo { x: 0 , y:1 }; // { dg-error "constructor is missing fields" }
}

---

I expected to see this happen:

• Emit error message, similiar to rustc .i.e.,
  • emit the name of initializer & field
• Error message emitted by rustc:

error[E0063]: missing field `y` in initializer of `Foo`
 --> <source>:7:13
  |
7 |     let x = Foo {  x:0}; // error: missing field: `y`
  |             ^^^ missing `y`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0063`.
Compiler returned: 1

---

Instead, this happened:

• No initializer & field information in error messge.
• This is the output of gccrs:

- missing field `y` in initializer of `Foo` // rustc output
+ error: constructor is missing fields [E0063] // gccrs output

➜  gccrs-build gcc/crab1 /home/mahad/Desktop/mahad/gccrs/gcc/testsuite/rust/compile/missing_constructor_fields.rs
/home/mahad/Desktop/mahad/gccrs/gcc/testsuite/rust/compile/missing_constructor_fields.rs:9:13: error: constructor is missing fields [E0063]
    9 |     let x = Foo { x: 0 , y:1 }; // { dg-error "constructor is missing fields" }
      |             ^~~

Analyzing compilation unit

Time variable                                   usr           sys          wall           GGC
 TOTAL                              :   0.00          0.00          0.00          146k
Extra diagnostic checks enabled; compiler may run slowly.
Configure with --enable-checking=release to disable checks.

---

Meta

• What version of Rust GCC were you using, git sha 5437803.
• gccrs (Compiler-Explorer-Build-gcc-2f91d511200bf85558c9013b09a458c06edd1e02-binutils-2.40) 13.0.1 20230417 (experimental)

---

[MahadMuhammad]

I tried to fix this issue by changes these lines of code by :

gccrs/gcc/rust/typecheck/rust-hir-type-check-struct.cc

Lines 150 to 155 in 5e735e9

	else if (!struct_expr.has_struct_base ())
	{
	rust_error_at (struct_expr.get_locus (),
	"constructor is missing fields");
	return;
	}

• To this :

rust_error_at (struct_expr.get_locus (), 
-  	      "constructor is missing fields");
+             "missing field %qs in initializer of %qs",
+              variant->get_fields ().at (0)->get_name ().c_str (), // This need to be changed
+              struct_path_resolved->get_name ().c_str ()); // This is giving right struct name

• But @CohenArthur said, we need some more changes to do this....