check task priority at compile time

before we were checking the priority at runtime. The compile time error message
when the priority is too high is kind of awful though.

2 files changed, 4 insertions, 6 deletions

diff --git a/macros/src/codegen.rs b/macros/src/codegen.rs
index 1d201c08..8b054ab5 100644
--- a/macros/src/codegen.rs
+++ b/macros/src/codegen.rs
@@ -1989,15 +1989,13 @@ fn pre_init(ctxt: &Context, app: &App, analysis: &Analysis) -> proc_macro2::Toke
         ))
     }
 
-    // TODO turn the assertions that check that the priority is not larger than what's supported by
-    // the device into compile errors
     let device = &app.args.device;
     let nvic_prio_bits = quote!(#device::NVIC_PRIO_BITS);
     for (handler, interrupt) in &app.interrupts {
         let name = interrupt.args.binds(handler);
         let priority = interrupt.args.priority;
         exprs.push(quote!(p.NVIC.enable(#device::Interrupt::#name);));
-        exprs.push(quote!(assert!(#priority <= (1 << #nvic_prio_bits));));
+        exprs.push(quote!(let _ = [(); ((1 << #nvic_prio_bits) - #priority as usize)];));
         exprs.push(quote!(p.NVIC.set_priority(
             #device::Interrupt::#name,
             ((1 << #nvic_prio_bits) - #priority) << (8 - #nvic_prio_bits),
@@ -2007,7 +2005,7 @@ fn pre_init(ctxt: &Context, app: &App, analysis: &Analysis) -> proc_macro2::Toke
     for (priority, dispatcher) in &analysis.dispatchers {
         let name = &dispatcher.interrupt;
         exprs.push(quote!(p.NVIC.enable(#device::Interrupt::#name);));
-        exprs.push(quote!(assert!(#priority <= (1 << #nvic_prio_bits));));
+        exprs.push(quote!(let _ = [(); ((1 << #nvic_prio_bits) - #priority as usize)];));
         exprs.push(quote!(p.NVIC.set_priority(
             #device::Interrupt::#name,
             ((1 << #nvic_prio_bits) - #priority) << (8 - #nvic_prio_bits),
diff --git a/macros/src/syntax.rs b/macros/src/syntax.rs
index 7f87f633..228d9588 100644
--- a/macros/src/syntax.rs
+++ b/macros/src/syntax.rs
@@ -1039,10 +1039,10 @@ fn parse_args(
                 }
 
                 let value = lit.value();
-                if value > u64::from(u8::MAX) {
+                if value > u64::from(u8::MAX) || value == 0 {
                     return Err(parse::Error::new(
                         lit.span(),
-                        "this literal must be in the range 0...255",
+                        "this literal must be in the range 1...255",
                     ));
                 }