zed-industries/zed · error

internal error: entered unreachable code

Error message

internal error: entered unreachable code

What it means

Metal atlas tile removal dispatches on the atlas texture kind to pick the right texture pool. `AtlasTextureKind::Subpixel` has no corresponding texture list in this atlas implementation, so the code hits an explicit `unreachable!()`. This means a tile with kind Subpixel was handed to an atlas that never allocates Subpixel textures — a caller/atlas mismatch.

Solutions

1. Skip tiles of kind Subpixel in the removal path (or route them to the correct atlas) instead of removing them from this atlas.
2. Extend the match to handle Subpixel with the correct texture pool if the atlas is supposed to support it.
3. Verify where the tile originated; only remove tiles that this atlas instance allocated.

Example fix

// before
AtlasTextureKind::Subpixel => unreachable!(),
// after
AtlasTextureKind::Subpixel => return, // subpixel tiles live in a different atlas

// before removing, ensure this atlas owns the tile kind
if matches!(tile_texture_kind(&tile), AtlasTextureKind::Subpixel) {
    return; // not managed by this atlas
}

fn is_removable_kind(kind: AtlasTextureKind) -> bool {
    matches!(kind, AtlasTextureKind::Monochrome | AtlasTextureKind::Polychrome)
}

When it happens

Trigger: Calling `remove(tile)` on a metal atlas with a tile whose `texture_id.kind` is `AtlasTextureKind::Subpixel`, typically because the tile was allocated by a different atlas/path or a kind was added without updating remove.

Common situations: Sprite/atlas eviction code that removes tiles regardless of kind, or a new AtlasTextureKind variant introduced without extending every match in metal_atlas.rs.

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AI-assisted analysis of zed-industries/zed@916fc2b8cb (2026-09-19). Data as JSON: /api/errors/c515caaa30c3e74b. Report an issue: GitHub.

Appendix: source

Thrown at crates/gpui_apple/src/metal_atlas.rs:69

    fn insert(
        &mut self,
        kind: AtlasTextureKind,
        size: Size<DevicePixels>,
        bytes: &[u8],
    ) -> Result<AtlasTile> {
        let tile = self.allocate(size, kind).context("failed to allocate")?;
        let texture = self.texture(tile.texture_id);
        texture.upload(tile.bounds, bytes);
        Ok(tile)
    }

    fn remove(&mut self, tile: AtlasTile) {
        let id = tile.texture_id;

        let textures = match id.kind {
            AtlasTextureKind::Monochrome => &mut self.monochrome_textures,
            AtlasTextureKind::Polychrome => &mut self.polychrome_textures,
            AtlasTextureKind::Subpixel => unreachable!(),
        };

        let Some(texture_slot) = textures
            .textures
            .iter_mut()
            .find(|texture| texture.as_ref().is_some_and(|v| v.id == id))
        else {
            return;
        };

        if let Some(mut texture) = texture_slot.take() {
            texture.allocator.deallocate(tile.tile_id.into());
            texture.decrement_ref_count();
            if texture.is_unreferenced() {
                textures.free_list.push(id.index as usize);
            } else {
                *texture_slot = Some(texture);
            }

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