Bump rust-toolchain to nightly-2021-03-15, unlocking for i in 0..n …

…loops!

crates/spirv-builder/src/test/control_flow.rs

@@ -377,9 +377,11 @@ pub fn main() {
 }"#);
 }
 
-// HACK(eddyb) test that `for` loop desugaring (with its call to `Iterator::next`
-// and matching on the resulting `Option`) works, without a working `Range`
-// iterator (due to the use of `mem::swap` and its block-wise implementation).
+// NOTE(eddyb) this tests `for` loop desugaring (with its call to `Iterator::next`
+// and matching on the resulting `Option`), without relying on a `Range` iterator.
+// More precisely, `Range` used to not compile, due to it using `mem::replace`,
+// which, before https://github.com/rust-lang/rust/pull/83022, used to just call
+// `mem::swap` (which has a block-wise optimization that can't work on SPIR-V).
 #[test]
 fn cf_for_with_custom_range_iter() {
     val(r#"
@@ -408,3 +410,14 @@ pub fn main(i: Input<i32>) {
 }
 "#);
 }
+
+#[test]
+fn cf_for_range() {
+    val(r#"
+#[spirv(fragment)]
+pub fn main(i: Input<i32>) {
+    for _ in 0..*i {
+    }
+}
+"#);
+}

examples/shaders/mouse-shader/src/lib.rs

@@ -226,9 +226,7 @@ pub fn main_fs(
         .intersect(mouse_circle)
     };
 
-    // FIXME(eddyb) use a `for i in 0..3` loop when that works.
-    let mut i = 0;
-    while i < 3 {
+    for i in 0..3 {
         painter.fill(
             mouse_button(i),
             RED.lerp(
@@ -242,7 +240,6 @@ pub fn main_fs(
                 ),
             ),
         );
-        i += 1;
     }
 
     painter.fill_with_contrast_border(

rust-toolchain

@@ -5,5 +5,5 @@
 # to the user in the error, instead of "error: invalid channel name '[toolchain]'".
 
 [toolchain]
-channel = "nightly-2021-03-11"
+channel = "nightly-2021-03-15"
 components = ["rust-src", "rustc-dev", "llvm-tools-preview"]