fix: Address unexpected Python behaviour in slicing, where end > star…

…t would panic instead of returning an empty byte slice

examples/sizes.txt

@@ -58,7 +58,7 @@ ssa2                                       95      87      87
 state_proxies/StateProxy                   87      83      83      
 string_ops                                 157     152     152     
 stubs/BigUInt                              172     112     112     
-stubs/Bytes                                928     164     164     
+stubs/Bytes                                1769    258     258     
 stubs/Uint64                               371     8       8       
 too_many_permutations                      108     107     107     
 transaction/Transaction                    914     864     864     

src/puya/awst/function_traverser.py

@@ -1,6 +1,5 @@
 import puya.awst.visitors
 from puya.awst import nodes as awst_nodes
-from puya.awst.visitors import T
 
 
 class FunctionTraverser(

src/puya/awst_build/eb/bytes.py

@@ -177,10 +177,36 @@ def slice_index(
         # since we evaluate self both as base and to get its length,
         # we need to create a temporary assignment in case it has side effects
         base = SingleEvaluation(self.expr)
-        slice_expr = SliceExpression(
+        begin_index_expr = _eval_slice_component(base, begin_index, location)
+        end_index_expr = _eval_slice_component(base, end_index, location)
+        if begin_index_expr is not None and end_index_expr is not None:
+            # special handling for if begin > end, will devolve into begin == end,
+            # which already returns the correct result of an empty bytes
+            # TODO: maybe we could improve the generated code if the above conversions weren't
+            #       isolated - ie, if we move this sort of checks to before the length
+            #       truncating checks
+            end_index_expr = IntrinsicCall(
+                op_code="select",
+                stack_args=[
+                    # false: end = end
+                    end_index_expr,
+                    # true: end = begin
+                    begin_index_expr,
+                    # condition: begin > end
+                    NumericComparisonExpression(
+                        lhs=begin_index_expr,
+                        operator=NumericComparison.gt,
+                        rhs=end_index_expr,
+                        source_location=location,
+                    ),
+                ],
+                wtype=wtypes.uint64_wtype,
+                source_location=end_index_expr.source_location,
+            )
+        slice_expr: Expression = SliceExpression(
             base=base,
-            begin_index=_eval_slice_component(base, begin_index, location),
-            end_index=_eval_slice_component(base, end_index, location),
+            begin_index=begin_index_expr,
+            end_index=end_index_expr,
             wtype=self.wtype,
             source_location=location,
         )

src/puya/ir/arc4_router.py

@@ -55,17 +55,24 @@ def call(
     )
 
 
-def load_abi_arg(
+def app_arg(
     index: int,
     wtype: wtypes.WType,
     location: SourceLocation,
-) -> awst_nodes.IntrinsicCall:
-    return awst_nodes.IntrinsicCall(
+) -> awst_nodes.Expression:
+    value = awst_nodes.IntrinsicCall(
         source_location=location,
-        wtype=wtype,
+        wtype=wtypes.bytes_wtype,
         op_code="txna",
         immediates=["ApplicationArgs", index],
     )
+    if wtype == wtypes.bytes_wtype:
+        return value
+    return awst_nodes.ReinterpretCast(
+        source_location=location,
+        expr=value,
+        wtype=wtype,
+    )
 
 
 def btoi(bytes_arg: awst_nodes.Expression, location: SourceLocation) -> awst_nodes.Expression:
@@ -572,11 +579,11 @@ def map_param_wtype_to_arc4_tuple_type(wtype: wtypes.WType) -> wtypes.WType:
         args_overflow_wtype = wtypes.ARC4Tuple.from_types(
             [map_param_wtype_to_arc4_tuple_type(a.wtype) for a in non_transaction_args[14:]]
         )
-        last_arg = load_abi_arg(15, args_overflow_wtype, location)
+        last_arg = app_arg(15, args_overflow_wtype, location)
 
     def get_arg(index: int, arg_wtype: wtypes.WType) -> awst_nodes.Expression:
         if index < 15:
-            return load_abi_arg(index, arg_wtype, location)
+            return app_arg(index, arg_wtype, location)
         else:
             if last_arg is None:
                 raise InternalError("last_arg should not be None if there are more than 15 args")
@@ -585,20 +592,20 @@ def get_arg(index: int, arg_wtype: wtypes.WType) -> awst_nodes.Expression:
     for arg in args:
         match arg.wtype:
             case wtypes.asset_wtype:
-                bytes_arg = get_arg(abi_arg_index, arg.wtype)
+                bytes_arg = get_arg(abi_arg_index, wtypes.bytes_wtype)
                 asset_index = btoi(bytes_arg, location)
                 asset_id = asset_id_at(asset_index, location)
                 yield asset_id
                 abi_arg_index += 1
 
             case wtypes.account_wtype:
-                bytes_arg = get_arg(abi_arg_index, arg.wtype)
+                bytes_arg = get_arg(abi_arg_index, wtypes.bytes_wtype)
                 account_index = btoi(bytes_arg, location)
                 account = account_at(account_index, location)
                 yield account
                 abi_arg_index += 1
             case wtypes.application_wtype:
-                bytes_arg = get_arg(abi_arg_index, arg.wtype)
+                bytes_arg = get_arg(abi_arg_index, wtypes.bytes_wtype)
                 application_index = btoi(bytes_arg, location)
                 application = application_at(application_index, location)
                 yield application

src/puya/ir/builder/main.py

@@ -43,6 +43,7 @@
     AVMBytesEncoding,
     bytes_enc_to_avm_bytes_enc,
     wtype_to_avm_type,
+    wtype_to_avm_types,
 )
 from puya.ir.utils import format_tuple_index
 from puya.parse import SourceLocation
@@ -306,6 +307,7 @@ def visit_intrinsic_call(self, call: awst_nodes.IntrinsicCall) -> TExpression:
                     source_location=call.source_location,
                     args=args,
                     immediates=list(call.immediates),
+                    types=wtype_to_avm_types(call.wtype),
                 )
 
     def visit_create_inner_transaction(self, call: awst_nodes.CreateInnerTransaction) -> None:

src/puya/ir/models.py

@@ -19,8 +19,8 @@
 
 def _check_stack_types(
     error_format: str,
-    target_types: list[AVMType],
-    source_types: list[AVMType],
+    target_types: Sequence[AVMType],
+    source_types: Sequence[AVMType],
     source_location: SourceLocation | None,
 ) -> None:
     if len(target_types) != len(source_types) or not all(
@@ -276,6 +276,25 @@ class Intrinsic(Op, ValueProvider):
     immediates: list[str | int] = attrs.field(factory=list)
     args: list[Value] = attrs.field(factory=list)
     comment: str | None = None  # used e.g. for asserts
+    _types: Sequence[AVMType] = attrs.field(converter=tuple[AVMType, ...])
+
+    @_types.default
+    def _default_types(self) -> tuple[AVMType, ...]:
+        return tuple(map(stack_type_to_avm_type, self.op_signature.returns))
+
+    @_types.validator
+    def _validate_types(self, _attribute: object, types: Sequence[AVMType]) -> None:
+        expected_types = self._default_types()
+        received_types = tuple(types)
+        desc = f"({self.op} {' '.join(map(str, self.immediates))}): "
+        _check_stack_types(
+            "Incompatible return types on Intrinsic"
+            + desc
+            + " received = {source_types}, expected = {target_types}",
+            expected_types,
+            received_types,
+            self.source_location,
+        )
 
     def _frozen_data(self) -> object:
         return self.op, tuple(self.immediates), tuple(self.args), self.comment
@@ -285,7 +304,7 @@ def accept(self, visitor: IRVisitor[T]) -> T:
 
     @property
     def types(self) -> Sequence[AVMType]:
-        return tuple(map(stack_type_to_avm_type, self.op_signature.returns))
+        return self._types
 
     @property
     def op_signature(self) -> OpSignature:

src/puya/ir/types_.py

@@ -58,6 +58,22 @@ def wtype_to_avm_type(
             )
 
 
+def wtype_to_avm_types(
+    expr_or_wtype: wtypes.WType | awst_nodes.Expression,
+    source_location: SourceLocation | None = None,
+) -> list[AVMType]:
+    if isinstance(expr_or_wtype, awst_nodes.Expression):
+        wtype = expr_or_wtype.wtype
+    else:
+        wtype = expr_or_wtype
+    if wtype == wtypes.void_wtype:
+        return []
+    elif isinstance(wtype, wtypes.WTuple):
+        return [wtype_to_avm_type(t, source_location) for t in wtype.types]
+    else:
+        return [wtype_to_avm_type(wtype, source_location)]
+
+
 def stack_type_to_avm_type(stack_type: StackType) -> AVMType:
     match stack_type:
         case StackType.uint64 | StackType.bool:

test_cases/arc4_types/out/Arc4MutationContract.destructured.ir

@@ -174,7 +174,7 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 let result#0: bytes = ((replace2 0) source#0 tmp%1#0)
                 let popped_location#0: uint64 = (+ length_minus_1#0 16u)
                 let tmp%2#0: uint64 = (getbit result#0 popped_location#0)
-                let popped#0: any = (setbit "\x00" 0u tmp%2#0)
+                let popped#0: bytes = (setbit "\x00" 0u tmp%2#0)
                 let result#0: bytes = (setbit result#0 popped_location#0 0u)
                 let tmp%3#0: uint64 = (+ length_minus_1#0 7u)
                 let tmp%4#0: uint64 = (/ tmp%3#0 8u)

test_cases/arc4_types/out/Arc4MutationContract.ssa.ir

@@ -796,8 +796,8 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 let result#0: bytes = ((replace2 0) source#0 tmp%1#0)
                 let popped_location#0: uint64 = (+ length_minus_1#0 16u)
                 let tmp%2#0: uint64 = (getbit result#0 popped_location#0)
-                let popped#0: any = (setbit "\x00" 0u tmp%2#0)
-                let result#1: any = (setbit result#0 popped_location#0 0u)
+                let popped#0: bytes = (setbit "\x00" 0u tmp%2#0)
+                let result#1: bytes = (setbit result#0 popped_location#0 0u)
                 let tmp%3#0: uint64 = (+ length_minus_1#0 7u)
                 let tmp%4#0: uint64 = (/ tmp%3#0 8u)
                 let tmp%5#0: uint64 = (+ 2u tmp%4#0)
@@ -878,7 +878,7 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
             block@7: // for_body_L110
                 let i#0: uint64 = range_item%7#1
                 let tmp%9#0: uint64 = (getbit new_items_bytes#0 i#0)
-                let result#3: any = (setbit result#4 write_offset#3 tmp%9#0)
+                let result#3: bytes = (setbit result#4 write_offset#3 tmp%9#0)
                 let write_offset#2: uint64 = (+ write_offset#3 1u)
                 goto block@8
             block@8: // for_footer_L110

test_cases/arc4_types/out/Arc4MutationContract.ssa.opt_pass_1.ir

@@ -655,8 +655,8 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 let result#0: bytes = ((replace2 0) source#0 tmp%1#0)
                 let popped_location#0: uint64 = (+ length_minus_1#0 16u)
                 let tmp%2#0: uint64 = (getbit result#0 popped_location#0)
-                let popped#0: any = (setbit "\x00" 0u tmp%2#0)
-                let result#1: any = (setbit result#0 popped_location#0 0u)
+                let popped#0: bytes = (setbit "\x00" 0u tmp%2#0)
+                let result#1: bytes = (setbit result#0 popped_location#0 0u)
                 let tmp%3#0: uint64 = (+ length_minus_1#0 7u)
                 let tmp%4#0: uint64 = (/ tmp%3#0 8u)
                 let tmp%5#0: uint64 = (+ 2u tmp%4#0)
@@ -736,7 +736,7 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 goto continue_looping%8#0 ? block@7 : block@10
             block@7: // for_body_L110
                 let tmp%9#0: uint64 = (getbit new_items_bytes#0 i#0)
-                let result#3: any = (setbit result#4 write_offset#3 tmp%9#0)
+                let result#3: bytes = (setbit result#4 write_offset#3 tmp%9#0)
                 let write_offset#2: uint64 = (+ write_offset#3 1u)
                 let range_item%7#3: uint64 = (+ i#0 ternary_result%6#2)
                 goto block@6

test_cases/arc4_types/out/Arc4MutationContract.ssa.opt_pass_10.ir

@@ -227,8 +227,8 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 let result#0: bytes = ((replace2 0) source#0 tmp%1#0)
                 let popped_location#0: uint64 = (+ length_minus_1#0 16u)
                 let tmp%2#0: uint64 = (getbit result#0 popped_location#0)
-                let popped#0: any = (setbit "\x00" 0u tmp%2#0)
-                let result#1: any = (setbit result#0 popped_location#0 0u)
+                let popped#0: bytes = (setbit "\x00" 0u tmp%2#0)
+                let result#1: bytes = (setbit result#0 popped_location#0 0u)
                 let tmp%3#0: uint64 = (+ length_minus_1#0 7u)
                 let tmp%4#0: uint64 = (/ tmp%3#0 8u)
                 let tmp%5#0: uint64 = (+ 2u tmp%4#0)
@@ -308,7 +308,7 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 goto continue_looping%8#0 ? block@7 : block@10
             block@7: // for_body_L110
                 let tmp%9#0: uint64 = (getbit new_items_bytes#0 i#0)
-                let result#3: any = (setbit result#4 write_offset#3 tmp%9#0)
+                let result#3: bytes = (setbit result#4 write_offset#3 tmp%9#0)
                 let write_offset#2: uint64 = (+ write_offset#3 1u)
                 let range_item%7#3: uint64 = (+ i#0 ternary_result%6#2)
                 goto block@6

test_cases/arc4_types/out/Arc4MutationContract.ssa.opt_pass_11.ir

@@ -218,8 +218,8 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 let result#0: bytes = ((replace2 0) source#0 tmp%1#0)
                 let popped_location#0: uint64 = (+ length_minus_1#0 16u)
                 let tmp%2#0: uint64 = (getbit result#0 popped_location#0)
-                let popped#0: any = (setbit "\x00" 0u tmp%2#0)
-                let result#1: any = (setbit result#0 popped_location#0 0u)
+                let popped#0: bytes = (setbit "\x00" 0u tmp%2#0)
+                let result#1: bytes = (setbit result#0 popped_location#0 0u)
                 let tmp%3#0: uint64 = (+ length_minus_1#0 7u)
                 let tmp%4#0: uint64 = (/ tmp%3#0 8u)
                 let tmp%5#0: uint64 = (+ 2u tmp%4#0)
@@ -299,7 +299,7 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 goto continue_looping%8#0 ? block@7 : block@10
             block@7: // for_body_L110
                 let tmp%9#0: uint64 = (getbit new_items_bytes#0 i#0)
-                let result#3: any = (setbit result#4 write_offset#3 tmp%9#0)
+                let result#3: bytes = (setbit result#4 write_offset#3 tmp%9#0)
                 let write_offset#2: uint64 = (+ write_offset#3 1u)
                 let range_item%7#3: uint64 = (+ i#0 ternary_result%6#2)
                 goto block@6

test_cases/arc4_types/out/Arc4MutationContract.ssa.opt_pass_12.ir

@@ -212,8 +212,8 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 let result#0: bytes = ((replace2 0) source#0 tmp%1#0)
                 let popped_location#0: uint64 = (+ length_minus_1#0 16u)
                 let tmp%2#0: uint64 = (getbit result#0 popped_location#0)
-                let popped#0: any = (setbit "\x00" 0u tmp%2#0)
-                let result#1: any = (setbit result#0 popped_location#0 0u)
+                let popped#0: bytes = (setbit "\x00" 0u tmp%2#0)
+                let result#1: bytes = (setbit result#0 popped_location#0 0u)
                 let tmp%3#0: uint64 = (+ length_minus_1#0 7u)
                 let tmp%4#0: uint64 = (/ tmp%3#0 8u)
                 let tmp%5#0: uint64 = (+ 2u tmp%4#0)
@@ -293,7 +293,7 @@ contract test_cases.arc4_types.mutation.Arc4MutationContract:
                 goto continue_looping%8#0 ? block@7 : block@10
             block@7: // for_body_L110
                 let tmp%9#0: uint64 = (getbit new_items_bytes#0 i#0)
-                let result#3: any = (setbit result#4 write_offset#3 tmp%9#0)
+                let result#3: bytes = (setbit result#4 write_offset#3 tmp%9#0)
                 let write_offset#2: uint64 = (+ write_offset#3 1u)
                 let range_item%7#3: uint64 = (+ i#0 ternary_result%6#2)
                 goto block@6