feat: better error for varargs failure in comptime

guppylang-internals/src/guppylang_internals/tracing/function.py

@@ -11,6 +11,7 @@
 from guppylang_internals.checker.errors.type_errors import TypeMismatchError
 from guppylang_internals.compiler.core import CompilerContext, DFContainer
 from guppylang_internals.compiler.expr_compiler import ExprCompiler
+from guppylang_internals.definition.custom import CustomFunctionDef
 from guppylang_internals.definition.value import CallableDef
 from guppylang_internals.diagnostic import Error
 from guppylang_internals.error import GuppyComptimeError, GuppyError, exception_hook
@@ -44,6 +45,13 @@ class TracingReturnError(Error):
     msg: str
 
 
+@dataclass(frozen=True)
+class VarArgsError(Error):
+    title: ClassVar[str] = "Varargs functions not supported in comptime"
+    message: ClassVar[str] = "{msg}"
+    msg: str
+
+
 def trace_function(
     python_func: Callable[..., Any],
     ty: FunctionType,
@@ -173,6 +181,12 @@ def trace_call(func: CallableDef, *args: Any) -> Any:
     # Update inouts
     # If the input types of the function aren't known, we can't check this.
     # This is the case for functions with a custom checker and no type annotations.
+    if isinstance(func, CustomFunctionDef) and not func.has_signature:
+        msg = f"Try wrapping `{func.name}` in a non-comptime @guppy function"
+        err = VarArgsError(call_node, msg)
+
+        raise GuppyError(err) from None
+
     if len(func.ty.inputs) != 0:
         for inp, arg, var in zip(func.ty.inputs, args, arg_vars, strict=True):
             if InputFlags.Inout in inp.flags:

tests/emulator/test_builder.py

@@ -152,7 +152,6 @@ def test_emulator_builder_immutability():
     assert builder.verbose is False
 
 
-
 def test_emulator_builder_reuse():
     """Test that the same builder can be used multiple times."""
     builder = EmulatorBuilder().with_name("reusable").with_verbose(True)

tests/error/tracing_errors/varargs.err

@@ -0,0 +1,7 @@
+Traceback (most recent call last):
+  File "$FILE", line 12, in <module>
+    main.compile()
+  File "$FILE", line 8, in main
+    barrier(qs)
+guppylang_internals.error.GuppyComptimeError: Varargs functions not supported in comptime
+Try wrapping `barrier` in a non-comptime @guppy function

tests/error/tracing_errors/varargs.py

@@ -0,0 +1,12 @@
+from guppylang import guppy
+from guppylang.std.quantum import qubit, h, discard_array
+from guppylang.std.builtins import array, barrier
+
+@guppy.comptime
+def main() -> None:
+    qs = array(qubit() for _ in range(5))
+    barrier(qs)
+    h(qs[0])
+    discard_array(qs)
+
+main.compile()

tests/integration/tracing/test_quantum.py

@@ -1,8 +1,8 @@
 from guppylang import qubit
 from guppylang.decorator import guppy
 from guppylang.std.angles import angle
-from guppylang.std.builtins import array
-from guppylang.std.quantum import h, measure, cx, rz
+from guppylang.std.builtins import array, barrier
+from guppylang.std.quantum import h, measure, cx, rz, discard_array
 import itertools
 
 
@@ -40,3 +40,20 @@ def test(qs: array[qubit, 10], theta: angle) -> None:
             theta /= 2
 
     validate(test.compile())
+
+
+def test_barrier_wrapper(validate):
+    """Test workaround for https://github.com/CQCL/guppylang/issues/1189"""
+
+    @guppy
+    def barrier_wrapper(qs: array[qubit, 5]) -> None:
+        barrier(qs)
+
+    @guppy.comptime
+    def main() -> None:
+        qs = array(qubit() for _ in range(5))
+        barrier_wrapper(qs)
+        h(qs[0])
+        discard_array(qs)
+
+    validate(main.compile())