Apply suggestions from code review

Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>

Author: erik-3milabs

spec/expr.typ

@@ -9,7 +9,7 @@
     assert(type(typ.at(1)) == int, message: "Array types need to have a constant dimension")
     typ = typ.at(0)
   }
-  assert(type(typ.at(0)) == str, message: "Array types need to have a regular type as base")
+  assert(type(typ) == str, message: "Array types need to have a regular type as base")
 }
 
 // Render a type to code
@@ -60,7 +60,7 @@
   "cast": 3, // cast
   "mul": 4,  // *
   "div": 5,  // /
-  "mod": 6,  // %
+  "mod": 6,  // mod
   "sum": 7,  // Σ
   "not": 8,  // not
   "sub": 9,  // -

spec/keccak.typ

@@ -39,7 +39,7 @@ The chip therefore contributes the following interaction to the lookup-argument:
 
 The address containing the state to be permuted is passed in as argument `A0 = x10`.
 The following constraints describe that this address is read into `addr` (@keccak:c:read_addr), from which `state_ptr` --- the collection of pointers to all lanes of the state --- is derived (@keccak:c:state_ptr).
-The state is then read into `input_state`, while the `output_state` is written back to the indicated address (@keccack:c:load_store_state).
+The state is then read into `input_state`, while the `output_state` is written back to the indicated address (@keccak:c:load_store_state).
 #render_constraint_table(chip, config, groups: "mem")
 
 Lastly, the input state is pushed to the Keccak-round function, while the output after 24 rounds is taken off the bus:

spec/tooling/chip.py

@@ -264,11 +264,15 @@ def typecheck(self, env: Environment) -> Type:
         elt = self.elt.typecheck(env)
         modulus = self.modulus.typecheck(env)
 
+        if isinstance(modulus, list) or not modulus.is_const():
         if isinstance(modulus, list) or not modulus.is_const():
             reporter.error(f"Invalid non-constant modulus: {self.modulus!r}")
+            return Range(0, 0)  # sentinel; error already recorded
         modulus = modulus.get_const()
         if modulus <= 0:
-            reporter.error(f"Invalid zero non-positive modulus: {self.modulus!r}")
+        if modulus <= 0:
+            reporter.error(f"Invalid non-positive modulus: {self.modulus!r}")
+            return Range(0, 0)  # sentinel; error already recorded
 
         if elt.is_const():
             elt = elt.get_const()