Unable to trace type-expectation error in Rust

Question

Repository
https://github.com/hunterlester/rusty_arcade

Versions
Rust: 1.7.0
sdl2: 0.16.1
sdl2_image: 0.16.0

Error

src/views/mod.rs:88:13: 93:23 error: mismatched types:
 expected `core::option::Option<sdl2::rect::Rect>`,
    found `sdl2::rect::Rect`
(expected enum `core::option::Option`,
    found struct `sdl2::rect::Rect`) [E0308]
src/views/mod.rs:88             Rectangle {
src/views/mod.rs:89                 x: 0.0,
src/views/mod.rs:90                 y: 0.0,
src/views/mod.rs:91                 w: self.player.rect.w,
src/views/mod.rs:92                 h: self.player.rect.h,
src/views/mod.rs:93             }.to_sdl(),
src/views/mod.rs:88:13: 93:23 help: run `rustc --explain E0308` to see  a detailed explanation
src/views/mod.rs:94:13: 94:38 error: mismatched types:
 expected `core::option::Option<sdl2::rect::Rect>`,
    found `sdl2::rect::Rect`
(expected enum `core::option::Option`,
    found struct `sdl2::rect::Rect`) [E0308]
src/views/mod.rs:94             self.player.rect.to_sdl()

Tracking it down
Lines 93 and 94 of the specified file.

phi.renderer.copy(&mut self.player.tex,
            Rectangle {
                x: 0.0,
                y: 0.0,
                w: self.player.rect.w,
                h: self.player.rect.h,
            }.to_sdl(), // Line 93
            self.player.rect.to_sdl() // Line 94
        );

I'm assuming this has something to do with what the .to_sdl() method is returning.

to_sdl method

impl Rectangle {
    pub fn to_sdl(self) -> SdlRect {
        assert!(self.w >= 0.0 && self.h >= 0.0);

        SdlRect::new(self.x as i32, self.y as i32, self.w as u32,  self.h as u32)
    }

to_sdl returns an SdlRect which is in use at top of file:

use sdl2::rect::Rect as SdlRect;

sdl2 source
https://github.com/AngryLawyer/rust-sdl2/blob/master/src/sdl2/rect.rs

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Rect {
    raw: ll::SDL_Rect,
}

impl Rect {

pub fn new(x: i32, y: i32, width: u32, height: u32) -> Rect {
    let raw = ll::SDL_Rect {
        x: clamp_position(x),
        y: clamp_position(y),
        w: clamp_size(width) as i32,
        h: clamp_size(height) as i32,
    };
    Rect { raw: raw }
}

I don't see where sdl2::rect::Rect is expected to be wrapped in a core::option::Option enum type.

If you happen to be familiar with the tutorial that I'm following, you'll notice that I'm using a different version of sdl2_image than specified in the tutorial because the specified has been yanked from Crates.

sdl2_image depends on a different version of sdl2 which I had to match in order to take care of other errors.

please copy the error as text and not as an image. – oli_obk Apr 04 '16 at 14:38 — oli_obk, Apr 04 '16 at 14:38

score 6 · Accepted Answer · answered Apr 04 '16 at 14:42

The error means that the expression self.player.rect.to_sdl() yields a SdlRect, but that whatever uses that value, expects to be given an Option<SdlRect>. You are calling the copy of sdl2::render::Renderer, which has the following arguments:

&mut self, texture: &Texture, src: Option<Rect>, dst: Option<Rect>

As you can see, you need to pass two Option<Rect>s. The sdl-crate's documentation even says why:

Copies a portion of the texture to the current rendering target.

If src is None, the entire texture is copied.

If dst is None, the texture will be stretched to fill the given rectangle.

Unable to trace type-expectation error in Rust

1 Answers1