feat: Add result function (#271)

Closes #270

guppylang/prelude/_internal.py

@@ -9,6 +9,7 @@
     ExprSynthesizer,
     check_call,
     check_num_args,
+    check_type_against,
     synthesize_call,
 )
 from guppylang.definition.custom import (
@@ -21,11 +22,11 @@
 from guppylang.error import GuppyError, GuppyTypeError, InternalGuppyError
 from guppylang.hugr_builder.hugr import UNDEFINED, OutPortV
 from guppylang.nodes import GlobalCall
-from guppylang.tys.arg import ConstArg
+from guppylang.tys.arg import ConstArg, TypeArg
 from guppylang.tys.builtin import bool_type, int_type, list_type
 from guppylang.tys.const import ConstValue
 from guppylang.tys.subst import Inst, Subst
-from guppylang.tys.ty import FunctionType, NumericType, Type, unify
+from guppylang.tys.ty import FunctionType, NoneType, NumericType, Type, unify
 
 
 class ConstInt(BaseModel):
@@ -270,6 +271,52 @@ def check(self, args: list[ast.expr], ty: Type) -> tuple[ast.expr, Subst]:
         return self._get_const_len(inst), subst
 
 
+class ResultChecker(CustomCallChecker):
+    """Call checker for the `result` function.
+
+    This is a temporary hack until we have implemented the proper results mechanism.
+    """
+
+    def synthesize(self, args: list[ast.expr]) -> tuple[ast.expr, Type]:
+        check_num_args(2, len(args), self.node)
+        [tag, value] = args
+        if not isinstance(tag, ast.Constant) or not isinstance(tag.value, int):
+            raise GuppyTypeError("Expected an int literal", tag)
+        value, ty = ExprSynthesizer(self.ctx).synthesize(value)
+        if ty.linear:
+            raise GuppyTypeError(
+                f"Cannot use value with linear type `{ty}` as a result", value
+            )
+        type_args = [
+            TypeArg(ty),
+            ConstArg(ConstValue(value=tag.value, ty=NumericType(NumericType.Kind.Nat))),
+        ]
+        call = GlobalCall(def_id=self.func.id, args=[value], type_args=type_args)
+        return with_loc(self.node, call), NoneType()
+
+    def check(self, args: list[ast.expr], ty: Type) -> tuple[ast.expr, Subst]:
+        expr, res_ty = self.synthesize(args)
+        subst, _ = check_type_against(res_ty, ty, self.node)
+        return expr, subst
+
+
+class ResultCompiler(CustomCallCompiler):
+    """Call compiler for the `result` function.
+
+    This is a temporary hack until we have implemented the proper results mechanism.
+    """
+
+    def compile(self, args: list[OutPortV]) -> list[OutPortV]:
+        op = ops.CustomOp(
+            extension="Results",
+            op_name="Result",
+            args=[arg.to_hugr() for arg in self.type_args],
+            parent=UNDEFINED,
+        )
+        self.graph.add_node(ops.OpType(op), inputs=args)
+        return []
+
+
 class NatTruedivCompiler(CustomCallCompiler):
     """Compiler for the `nat.__truediv__` method."""
 

guppylang/prelude/builtins.py

@@ -23,6 +23,8 @@
     FloatModCompiler,
     IntTruedivCompiler,
     NatTruedivCompiler,
+    ResultChecker,
+    ResultCompiler,
     ReversingChecker,
     UnsupportedChecker,
     float_op,
@@ -611,6 +613,11 @@ def __getitem__(self: array[T, n], idx: int) -> T: ...
     def __len__(self: array[T, n]) -> int: ...
 
 
+# TODO: This is a temporary hack until we have implemented the proper results mechanism.
+@guppy.custom(builtins, ResultCompiler(), ResultChecker(), higher_order_value=False)
+def result(tag, value): ...
+
+
 @guppy.custom(builtins, checker=DunderChecker("__abs__"), higher_order_value=False)
 def abs(x): ...
 

tests/error/misc_errors/result_tag_not_int.err

@@ -0,0 +1,7 @@
+Guppy compilation failed. Error in file $FILE:7
+
+5:    @compile_guppy
+6:    def foo(x: int) -> None:
+7:        result((), x)
+                 ^^
+GuppyTypeError: Expected an int literal

tests/error/misc_errors/result_tag_not_int.py

@@ -0,0 +1,7 @@
+from guppylang.prelude.builtins import result
+from tests.util import compile_guppy
+
+
+@compile_guppy
+def foo(x: int) -> None:
+    result((), x)

tests/error/misc_errors/result_tag_not_static.err

@@ -0,0 +1,7 @@
+Guppy compilation failed. Error in file $FILE:7
+
+5:    @compile_guppy
+6:    def foo(x: int, y: bool) -> None:
+7:        result(x, y)
+                 ^
+GuppyTypeError: Expected an int literal

tests/error/misc_errors/result_tag_not_static.py

@@ -0,0 +1,7 @@
+from guppylang.prelude.builtins import result
+from tests.util import compile_guppy
+
+
+@compile_guppy
+def foo(x: int, y: bool) -> None:
+    result(x, y)

tests/error/misc_errors/result_value_linear.err

@@ -0,0 +1,7 @@
+Guppy compilation failed. Error in file $FILE:14
+
+12:    @guppy(module)
+13:    def foo(q: qubit) -> None:
+14:        result(0, q)
+                     ^
+GuppyTypeError: Cannot use value with linear type `qubit` as a result

tests/error/misc_errors/result_value_linear.py

@@ -0,0 +1,17 @@
+import guppylang.prelude.quantum as quantum
+from guppylang.decorator import guppy
+from guppylang.module import GuppyModule
+from guppylang.prelude.builtins import result
+from guppylang.prelude.quantum import qubit
+
+
+module = GuppyModule("test")
+module.load(quantum)
+
+
+@guppy(module)
+def foo(q: qubit) -> None:
+    result(0, q)
+
+
+module.compile()

tests/integration/test_result.py

@@ -0,0 +1,50 @@
+from hugr.serialization import ops
+
+from guppylang.decorator import guppy
+from guppylang.module import GuppyModule
+from guppylang.prelude.builtins import result
+from tests.util import compile_guppy
+
+
+def test_single(validate):
+    @compile_guppy
+    def main(x: int) -> None:
+        result(0, x)
+
+    validate(main)
+
+
+def test_value(validate):
+    @compile_guppy
+    def main(x: int) -> None:
+        return result(0, x)
+
+    validate(main)
+
+
+def test_nested(validate):
+    @compile_guppy
+    def main(x: int, y: float, z: bool) -> None:
+        result(42, (x, (y, z)))
+
+    validate(main)
+
+
+def test_multi(validate):
+    @compile_guppy
+    def main(x: int, y: float, z: bool) -> None:
+        result(0, x)
+        result(1, y)
+        result(2, z)
+
+    validate(main)
+
+
+def test_same_tag(validate):
+    @compile_guppy
+    def main(x: int, y: float, z: bool) -> None:
+        result(0, x)
+        result(0, y)
+        result(0, z)
+
+    validate(main)