refactor(port_arm_m): use Range: const Iterator and const_for

Author: yvt

src/r3_port_arm_m/src/lib.rs

@@ -1,12 +1,15 @@
+#![feature(const_intoiterator_identity)]
 #![feature(generic_const_exprs)]
 #![feature(const_refs_to_cell)]
 #![feature(const_trait_impl)]
 #![feature(naked_functions)]
 #![feature(const_mut_refs)]
 #![feature(slice_ptr_get)]
 #![feature(slice_ptr_len)]
+#![feature(const_iter)]
 #![feature(decl_macro)]
 #![feature(asm_const)]
+#![feature(const_for)]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![cfg_attr(
     feature = "doc",

src/r3_port_arm_m/src/rt/imp.rs

@@ -15,22 +15,19 @@ pub type InterruptHandlerTable = [InterruptHandler; NUM_INTERRUPTS];
 /// Used by `use_port!`
 pub const fn make_interrupt_handler_table<Traits: KernelTraits>() -> InterruptHandlerTable {
     let mut table = [InterruptHandler { undefined: 0 }; NUM_INTERRUPTS];
-    let mut i = 0;
 
-    // `for` is unusable in `const fn` [ref:const_for]
-    while i < table.len() {
+    // `[T]::iter_mut` is unusable in `const fn` [ref:const_slice_iter]
+    // `core::array::from_fn` is not `const fn` [ref:const_array_from_fn]
+    for i in 0..table.len() {
         table[i] = if let Some(x) = Traits::INTERRUPT_HANDLERS.get(i + 16) {
             InterruptHandler { defined: x }
         } else {
             InterruptHandler { undefined: 0 }
         };
-        i += 1;
     }
 
     // Disallow registering in range `0..16` except for SysTick
-    i = 0;
-    // `for` is unusable in `const fn` [ref:const_for]
-    while i < 16 {
+    for i in 0..16 {
         if i != INTERRUPT_SYSTICK {
             // TODO: This check trips even if no handler is registered at `i`
             #[cfg(any())]
@@ -40,7 +37,6 @@ pub const fn make_interrupt_handler_table<Traits: KernelTraits>() -> InterruptHa
                 disallowed except for SysTick"
             );
         }
-        i += 1;
     }
 
     table