codegen: LOOP exits on index==limit (Forth 2012 boundary crossing)

Rust 1.95 promoted collapsible_match and map_unwrap_or; CI runs
-D warnings so they break the build. Collapse nested `if`s into
match guards across codegen/optimizer/export, and swap
map().unwrap_or(..) for map_or / is_ok_and.

crates/core/src/codegen.rs

@@ -1088,10 +1088,12 @@ fn emit_do_loop(f: &mut Function, body: &[IrOp], is_plus_loop: bool, ctx: &mut E
                 .instruction(&Instruction::End);
         }
 
-        // if index >= limit, exit
+        // Forth 2012: LOOP exits when the index crosses the boundary between
+        // limit-1 and limit. With step +1 that is exactly new_index == limit
+        // in wraparound arithmetic — start >= limit must wrap, not exit early.
         f.instruction(&Instruction::LocalGet(index_local))
             .instruction(&Instruction::LocalGet(limit_local))
-            .instruction(&Instruction::I32GeS)
+            .instruction(&Instruction::I32Eq)
             .instruction(&Instruction::BrIf(1)) // break to $exit
             .instruction(&Instruction::Br(0)) // continue loop
             .instruction(&Instruction::End) // end loop
@@ -1897,7 +1899,8 @@ fn emit_promoted_op(f: &mut Function, op: &IrOp, sim: &mut StackSim) {
                 // Fix up stack for next iteration (LOOP body is stack-neutral)
                 emit_promoted_loop_fixup(f, sim, &loop_top_stack);
 
-                // LOOP: increment by 1, check >= limit
+                // LOOP: increment by 1, exit when new_index == limit
+                // (Forth 2012 boundary crossing; start >= limit wraps around)
                 f.instruction(&Instruction::LocalGet(index_local));
                 f.instruction(&Instruction::I32Const(1));
                 f.instruction(&Instruction::I32Add);
@@ -1905,7 +1908,7 @@ fn emit_promoted_op(f: &mut Function, op: &IrOp, sim: &mut StackSim) {
 
                 f.instruction(&Instruction::LocalGet(index_local));
                 f.instruction(&Instruction::LocalGet(limit_local));
-                f.instruction(&Instruction::I32GeS);
+                f.instruction(&Instruction::I32Eq);
                 f.instruction(&Instruction::BrIf(1)); // break to $exit
             }
 
@@ -2012,14 +2015,12 @@ fn emit_promoted_op(f: &mut Function, op: &IrOp, sim: &mut StackSim) {
             // Outside loops, RFetch shouldn't appear in promoted code
         }
 
-        IrOp::LoopJ => {
+        IrOp::LoopJ if sim.loop_index_stack.len() >= 2 => {
-            if sim.loop_index_stack.len() >= 2 {
+            let (outer_index, _) = sim.loop_index_stack[sim.loop_index_stack.len() - 2];
-                let (outer_index, _) = sim.loop_index_stack[sim.loop_index_stack.len() - 2];
+            let result = sim.alloc();
-                let result = sim.alloc();
+            f.instruction(&Instruction::LocalGet(outer_index));
-                f.instruction(&Instruction::LocalGet(outer_index));
+            f.instruction(&Instruction::LocalSet(result));
-                f.instruction(&Instruction::LocalSet(result));
+            sim.push(result);
-                sim.push(result);
-            }
         }
 
         IrOp::Exit => {
@@ -2147,15 +2148,15 @@ fn needs_f64_locals(ops: &[IrOp]) -> bool {
                     return true;
                 }
             }
-            IrOp::DoLoop { body, .. } | IrOp::BeginUntil { body } | IrOp::BeginAgain { body } => {
+            IrOp::DoLoop { body, .. } | IrOp::BeginUntil { body } | IrOp::BeginAgain { body }
-                if needs_f64_locals(body) {
+                if needs_f64_locals(body) =>
-                    return true;
+            {
-                }
+                return true;
             }
-            IrOp::BeginWhileRepeat { test, body } => {
+            IrOp::BeginWhileRepeat { test, body }
-                if needs_f64_locals(test) || needs_f64_locals(body) {
+                if needs_f64_locals(test) || needs_f64_locals(body) =>
-                    return true;
+            {
-                }
+                return true;
             }
             IrOp::BeginDoubleWhileRepeat {
                 outer_test,
@@ -2209,15 +2210,15 @@ fn body_needs_return_stack(ops: &[IrOp]) -> bool {
                     return true;
                 }
             }
-            IrOp::DoLoop { body, .. } | IrOp::BeginUntil { body } | IrOp::BeginAgain { body } => {
+            IrOp::DoLoop { body, .. } | IrOp::BeginUntil { body } | IrOp::BeginAgain { body }
-                if body_needs_return_stack(body) {
+                if body_needs_return_stack(body) =>
-                    return true;
+            {
-                }
+                return true;
             }
-            IrOp::BeginWhileRepeat { test, body } => {
+            IrOp::BeginWhileRepeat { test, body }
-                if body_needs_return_stack(test) || body_needs_return_stack(body) {
+                if body_needs_return_stack(test) || body_needs_return_stack(body) =>
-                    return true;
+            {
-                }
+                return true;
             }
             IrOp::BeginDoubleWhileRepeat {
                 outer_test,
@@ -2831,9 +2832,11 @@ fn emit_consolidated_do_loop(
                 .instruction(&Instruction::End);
         }
 
+        // Forth 2012 boundary crossing: exit when new_index == limit
+        // (start >= limit wraps around instead of exiting early).
         f.instruction(&Instruction::LocalGet(index_local))
             .instruction(&Instruction::LocalGet(limit_local))
-            .instruction(&Instruction::I32GeS)
+            .instruction(&Instruction::I32Eq)
             .instruction(&Instruction::BrIf(1))
             .instruction(&Instruction::Br(0))
             .instruction(&Instruction::End)

crates/core/src/export.rs

@@ -131,10 +131,8 @@ pub fn export_module(
 fn collect_external_calls(ops: &[IrOp], ir_ids: &HashSet<WordId>, host_ids: &mut HashSet<WordId>) {
     for op in ops {
         match op {
-            IrOp::Call(id) | IrOp::TailCall(id) => {
+            IrOp::Call(id) | IrOp::TailCall(id) if !ir_ids.contains(id) => {
-                if !ir_ids.contains(id) {
+                host_ids.insert(*id);
-                    host_ids.insert(*id);
-                }
             }
             IrOp::If {
                 then_body,

crates/core/src/optimizer.rs

@@ -591,15 +591,15 @@ fn contains_call_to(ops: &[IrOp], target: WordId) -> bool {
                     return true;
                 }
             }
-            IrOp::DoLoop { body, .. } | IrOp::BeginUntil { body } | IrOp::BeginAgain { body } => {
+            IrOp::DoLoop { body, .. } | IrOp::BeginUntil { body } | IrOp::BeginAgain { body }
-                if contains_call_to(body, target) {
+                if contains_call_to(body, target) =>
-                    return true;
+            {
-                }
+                return true;
             }
-            IrOp::BeginWhileRepeat { test, body } => {
+            IrOp::BeginWhileRepeat { test, body }
-                if contains_call_to(test, target) || contains_call_to(body, target) {
+                if contains_call_to(test, target) || contains_call_to(body, target) =>
-                    return true;
+            {
-                }
+                return true;
             }
             IrOp::BeginDoubleWhileRepeat {
                 outer_test,
@@ -651,15 +651,13 @@ fn contains_exit(ops: &[IrOp]) -> bool {
                     return true;
                 }
             }
-            IrOp::DoLoop { body, .. } | IrOp::BeginUntil { body } | IrOp::BeginAgain { body } => {
+            IrOp::DoLoop { body, .. } | IrOp::BeginUntil { body } | IrOp::BeginAgain { body }
-                if contains_exit(body) {
+                if contains_exit(body) =>
-                    return true;
+            {
-                }
+                return true;
             }
-            IrOp::BeginWhileRepeat { test, body } => {
+            IrOp::BeginWhileRepeat { test, body } if contains_exit(test) || contains_exit(body) => {
-                if contains_exit(test) || contains_exit(body) {
+                return true;
-                    return true;
-                }
             }
             _ => {}
         }

crates/core/src/outer.rs

@@ -397,8 +397,7 @@ impl<R: Runtime> ForthVM<R> {
                 use std::time::{SystemTime, UNIX_EPOCH};
                 let seed = SystemTime::now()
                     .duration_since(UNIX_EPOCH)
-                    .map(|d| d.as_nanos() as u64)
+                    .map_or(0xDEAD_BEEF_CAFE_BABE, |d| d.as_nanos() as u64);
-                    .unwrap_or(0xDEAD_BEEF_CAFE_BABE);
                 Arc::new(Mutex::new(if seed == 0 {
                     0xDEAD_BEEF_CAFE_BABE
                 } else {

crates/core/tests/comparison.rs

@@ -26,8 +26,7 @@ fn probe_gforth(candidate: &str) -> bool {
         .arg("-e")
         .arg("bye")
         .output()
-        .map(|o| o.status.success())
+        .is_ok_and(|o| o.status.success())
-        .unwrap_or(false)
 }
 
 fn find_gforth() -> Option<&'static str> {