Idea: constraints should only have placeholders

They were exposed on AST, causing confusion.
Now they're only used in constraints.

TODO.md

@@ -28,3 +28,8 @@
   - Functions don't seem to be a thing on typing level yet?
   - Related to the FIXME in phasm_type3?
   - Type constuctor should also be able to constuct placeholders - somehow.
+
+
+- Check placeholders only used in constraints and constraintgenerator
+- Simply typed check in compiler:
+  - isinstance(element.type3, type3types.Type3) => element.type3 is not None

phasm/ourlang.py

@@ -6,7 +6,6 @@ from typing import Dict, Iterable, List, Optional, Union
 
 from . import prelude
 from .type3.functions import FunctionSignature, TypeVariableContext
-from .type3.placeholders import PlaceholderForType, Type3OrPlaceholder
 from .type3.typeclasses import Type3ClassMethod
 from .type3.types import Type3
 
@@ -17,10 +16,10 @@ class Expression:
     """
     __slots__ = ('type3', )
 
-    type3: Type3OrPlaceholder
+    type3: Type3 | None
 
     def __init__(self) -> None:
-        self.type3 = PlaceholderForType([self])
+        self.type3 = None
 
 class Constant(Expression):
     """
@@ -198,10 +197,10 @@ class AccessStructMember(Expression):
     __slots__ = ('varref', 'struct_type3', 'member', )
 
     varref: VariableReference
-    struct_type3: Type3OrPlaceholder
+    struct_type3: Type3
     member: str
 
-    def __init__(self, varref: VariableReference,  struct_type3: Type3OrPlaceholder, member: str) -> None:
+    def __init__(self, varref: VariableReference,  struct_type3: Type3, member: str) -> None:
         super().__init__()
 
         self.varref = varref
@@ -284,7 +283,7 @@ class FunctionParam:
     __slots__ = ('name', 'type3', )
 
     name: str
-    type3: Type3OrPlaceholder
+    type3: Type3
 
     def __init__(self, name: str, type3: Type3) -> None:
         self.name = name

phasm/type3/constraints.py

@@ -3,10 +3,11 @@ This module contains possible constraints generated based on the AST
 
 These need to be resolved before the program can be compiled.
 """
-from typing import Dict, List, Optional, Tuple, Union
+from typing import Dict, Iterable, List, Optional, Tuple, Union
 
 from .. import ourlang, prelude
 from . import placeholders, typeclasses, types
+from .placeholders import PlaceholderForType
 
 
 class Error:
@@ -32,13 +33,13 @@ class RequireTypeSubstitutes:
     typing of the program, so this constraint can be updated.
     """
 
-SubstitutionMap = Dict[placeholders.PlaceholderForType, types.Type3]
+SubstitutionMap = Dict[PlaceholderForType, types.Type3]
 
 NewConstraintList = List['ConstraintBase']
 
 CheckResult = Union[None, SubstitutionMap, Error, NewConstraintList, RequireTypeSubstitutes]
 
-HumanReadableRet = Tuple[str, Dict[str, Union[str, ourlang.Expression, types.Type3, placeholders.PlaceholderForType]]]
+HumanReadableRet = Tuple[str, Dict[str, Union[str, ourlang.Expression, types.Type3, PlaceholderForType]]]
 
 class Context:
     """
@@ -98,9 +99,9 @@ class SameTypeConstraint(ConstraintBase):
     """
     __slots__ = ('type_list', )
 
-    type_list: List[placeholders.Type3OrPlaceholder]
+    type_list: List[PlaceholderForType]
 
-    def __init__(self, *type_list: placeholders.Type3OrPlaceholder, comment: Optional[str] = None) -> None:
+    def __init__(self, *type_list: PlaceholderForType, comment: Optional[str] = None) -> None:
         super().__init__(comment=comment)
 
         assert len(type_list) > 1
@@ -110,18 +111,10 @@ class SameTypeConstraint(ConstraintBase):
         known_types: List[types.Type3] = []
         phft_list = []
         for typ in self.type_list:
-            if isinstance(typ, types.Type3):
-                known_types.append(typ)
-                continue
-
-            if isinstance(typ, placeholders.PlaceholderForType):
             if typ.resolve_as is not None:
                 known_types.append(typ.resolve_as)
             else:
                 phft_list.append(typ)
-                continue
-
-            raise NotImplementedError(typ)
 
         if not known_types:
             return RequireTypeSubstitutes()
@@ -157,7 +150,7 @@ class SameTypeConstraint(ConstraintBase):
         return f'SameTypeConstraint({args}, comment={repr(self.comment)})'
 
 class TupleMatchConstraint(ConstraintBase):
-    def __init__(self, exp_type: placeholders.Type3OrPlaceholder, args: List[placeholders.Type3OrPlaceholder], comment: str):
+    def __init__(self, exp_type: PlaceholderForType, args: Iterable[PlaceholderForType], comment: str):
         super().__init__(comment=comment)
 
         self.exp_type = exp_type
@@ -165,7 +158,7 @@ class TupleMatchConstraint(ConstraintBase):
 
     def check(self) -> CheckResult:
         exp_type = self.exp_type
-        if isinstance(exp_type, placeholders.PlaceholderForType):
+        if isinstance(exp_type, PlaceholderForType):
             if exp_type.resolve_as is None:
                 return RequireTypeSubstitutes()
 
@@ -205,13 +198,13 @@ class MustImplementTypeClassConstraint(ConstraintBase):
 
     context: Context
     type_class3: Union[str, typeclasses.Type3Class]
-    types: list[placeholders.Type3OrPlaceholder]
+    types: list[PlaceholderForType]
 
     DATA = {
         'bytes': {'Foldable'},
     }
 
-    def __init__(self, context: Context, type_class3: Union[str, typeclasses.Type3Class], types: list[placeholders.Type3OrPlaceholder], comment: Optional[str] = None) -> None:
+    def __init__(self, context: Context, type_class3: Union[str, typeclasses.Type3Class], types: list[PlaceholderForType], comment: Optional[str] = None) -> None:
         super().__init__(comment=comment)
 
         self.context = context
@@ -221,10 +214,10 @@ class MustImplementTypeClassConstraint(ConstraintBase):
     def check(self) -> CheckResult:
         typ_list = []
         for typ in self.types:
-            if isinstance(typ, placeholders.PlaceholderForType) and typ.resolve_as is not None:
+            if isinstance(typ, PlaceholderForType) and typ.resolve_as is not None:
                 typ = typ.resolve_as
 
-            if isinstance(typ, placeholders.PlaceholderForType):
+            if isinstance(typ, PlaceholderForType):
                 return RequireTypeSubstitutes()
 
             typ_list.append(typ)
@@ -266,12 +259,12 @@ class LiteralFitsConstraint(ConstraintBase):
     """
     __slots__ = ('type3', 'literal', )
 
-    type3: placeholders.Type3OrPlaceholder
+    type3: PlaceholderForType
     literal: Union[ourlang.ConstantPrimitive, ourlang.ConstantBytes, ourlang.ConstantTuple, ourlang.ConstantStruct]
 
     def __init__(
             self,
-            type3: placeholders.Type3OrPlaceholder,
+            type3: PlaceholderForType,
             literal: Union[ourlang.ConstantPrimitive, ourlang.ConstantBytes, ourlang.ConstantTuple, ourlang.ConstantStruct],
             comment: Optional[str] = None,
         ) -> None:
@@ -295,7 +288,7 @@ class LiteralFitsConstraint(ConstraintBase):
             'f64': None,
         }
 
-        if isinstance(self.type3, placeholders.PlaceholderForType):
+        if isinstance(self.type3, PlaceholderForType):
             if self.type3.resolve_as is None:
                 return RequireTypeSubstitutes()
 
@@ -348,8 +341,12 @@ class LiteralFitsConstraint(ConstraintBase):
                     LiteralFitsConstraint(x, y)
                     for x, y in zip(tp_args, self.literal.value, strict=True)
                 )
+
+                # Generate placeholders so each Literal expression
+                # gets updated when we figure out the type of the
+                # expression the literal is used in
                 res.extend(
-                    SameTypeConstraint(x, y.type3)
+                    SameTypeConstraint(x, PlaceholderForType([y]))
                     for x, y in zip(tp_args, self.literal.value, strict=True)
                 )
 
@@ -371,8 +368,12 @@ class LiteralFitsConstraint(ConstraintBase):
                     LiteralFitsConstraint(sa_type, y)
                     for y in self.literal.value
                 )
+
+                # Generate placeholders so each Literal expression
+                # gets updated when we figure out the type of the
+                # expression the literal is used in
                 res.extend(
-                    SameTypeConstraint(sa_type, y.type3)
+                    SameTypeConstraint(sa_type, PlaceholderForType([y]))
                     for y in self.literal.value
                 )
 
@@ -396,8 +397,12 @@ class LiteralFitsConstraint(ConstraintBase):
                 LiteralFitsConstraint(x, y)
                 for x, y in zip(st_args.values(), self.literal.value, strict=True)
             )
+
+            # Generate placeholders so each Literal expression
+            # gets updated when we figure out the type of the
+            # expression the literal is used in
             res.extend(
-                SameTypeConstraint(x_t, y.type3, comment=f'{self.literal.struct_name}.{x_n}')
+                SameTypeConstraint(x_t, PlaceholderForType([y]), comment=f'{self.literal.struct_name}.{x_n}')
                 for (x_n, x_t, ), y in zip(st_args.items(), self.literal.value, strict=True)
             )
 
@@ -421,24 +426,31 @@ class CanBeSubscriptedConstraint(ConstraintBase):
     """
     A value that is subscipted, i.e. a[0] (tuple) or a[b] (static array)
     """
-    __slots__ = ('ret_type3', 'type3', 'index', 'index_type3', )
+    __slots__ = ('ret_type3', 'type3', 'index', 'index_phft', )
 
-    ret_type3: placeholders.Type3OrPlaceholder
+    ret_type3: PlaceholderForType
-    type3: placeholders.Type3OrPlaceholder
+    type3: PlaceholderForType
     index: ourlang.Expression
-    index_type3: placeholders.Type3OrPlaceholder
+    index_phft: PlaceholderForType
 
-    def __init__(self, ret_type3: placeholders.Type3OrPlaceholder, type3: placeholders.Type3OrPlaceholder, index: ourlang.Expression, comment: Optional[str] = None) -> None:
+    def __init__(
+            self,
+            ret_type3: PlaceholderForType,
+            type3: PlaceholderForType,
+            index: ourlang.Expression,
+            index_phft: PlaceholderForType,
+            comment: Optional[str] = None,
+        ) -> None:
         super().__init__(comment=comment)
 
         self.ret_type3 = ret_type3
         self.type3 = type3
         self.index = index
-        self.index_type3 = index.type3
+        self.index_phft = index_phft
 
     def check(self) -> CheckResult:
         exp_type = self.type3
-        if isinstance(exp_type, placeholders.PlaceholderForType):
+        if isinstance(exp_type, PlaceholderForType):
             if exp_type.resolve_as is None:
                 return RequireTypeSubstitutes()
 
@@ -451,7 +463,7 @@ class CanBeSubscriptedConstraint(ConstraintBase):
                 sa_type, sa_len = sa_args
 
                 result: List[ConstraintBase] = [
-                    SameTypeConstraint(prelude.u32, self.index_type3, comment='([]) :: Subscriptable a => a b -> u32 -> b'),
+                    SameTypeConstraint(prelude.u32, self.index_phft, comment='([]) :: Subscriptable a => a b -> u32 -> b'),
                     SameTypeConstraint(sa_type, self.ret_type3, comment='([]) :: Subscriptable a => a b -> u32 -> b'),
                 ]
 
@@ -478,13 +490,13 @@ class CanBeSubscriptedConstraint(ConstraintBase):
                     return Error('Tuple index out of range')
 
                 return [
-                    SameTypeConstraint(prelude.u32, self.index_type3, comment=f'Tuple subscript index {self.index.value}'),
+                    SameTypeConstraint(prelude.u32, self.index_phft, comment=f'Tuple subscript index {self.index.value}'),
                     SameTypeConstraint(tp_args[self.index.value], self.ret_type3, comment=f'Tuple subscript index {self.index.value}'),
                 ]
 
         if exp_type is prelude.bytes_:
             return [
-                SameTypeConstraint(prelude.u32, self.index_type3, comment='([]) :: bytes -> u32 -> u8'),
+                SameTypeConstraint(prelude.u32, self.index_phft, comment='([]) :: bytes -> u32 -> u8'),
                 SameTypeConstraint(prelude.u8, self.ret_type3, comment='([]) :: bytes -> u32 -> u8'),
             ]
 

phasm/type3/constraintsgenerator.py

@@ -19,6 +19,7 @@ from .constraints import (
     SameTypeConstraint,
     TupleMatchConstraint,
 )
+from .placeholders import PlaceholderForType
 
 ConstraintGenerator = Generator[ConstraintBase, None, None]
 
@@ -28,23 +29,23 @@ def phasm_type3_generate_constraints(inp: ourlang.Module) -> List[ConstraintBase
 
     return [*module(ctx, inp)]
 
-def constant(ctx: Context, inp: ourlang.Constant) -> ConstraintGenerator:
+def constant(ctx: Context, inp: ourlang.Constant, phft: placeholders.PlaceholderForType) -> ConstraintGenerator:
     if isinstance(inp, (ourlang.ConstantPrimitive, ourlang.ConstantBytes, ourlang.ConstantTuple, ourlang.ConstantStruct)):
         yield LiteralFitsConstraint(
-            inp.type3, inp,
+            phft, inp,
             comment='The given literal must fit the expected type'
         )
         return
 
     raise NotImplementedError(constant, inp)
 
-def expression(ctx: Context, inp: ourlang.Expression) -> ConstraintGenerator:
+def expression(ctx: Context, inp: ourlang.Expression, phft: placeholders.PlaceholderForType) -> ConstraintGenerator:
     if isinstance(inp, ourlang.Constant):
-        yield from constant(ctx, inp)
+        yield from constant(ctx, inp, phft)
         return
 
     if isinstance(inp, ourlang.VariableReference):
-        yield SameTypeConstraint(inp.variable.type3, inp.type3,
+        yield SameTypeConstraint(inp.variable.type3, phft,
             comment=f'typeOf("{inp.variable.name}") == typeOf({inp.variable.name})')
         return
 
@@ -60,8 +61,14 @@ def expression(ctx: Context, inp: ourlang.Expression) -> ConstraintGenerator:
             if isinstance(x, functions.TypeVariable)
         }
 
-        for call_arg in arguments:
+        arg_placeholders = {
-            yield from expression(ctx, call_arg)
+            arg_expr: PlaceholderForType([arg_expr])
+            for arg_expr in arguments
+        }
+        arg_placeholders[inp] = phft
+
+        for arg_expr in arguments:
+            yield from expression(ctx, arg_expr, arg_placeholders[arg_expr])
 
         for constraint in signature.context.constraints:
             if isinstance(constraint, functions.Constraint_TypeClassInstanceExists):
@@ -81,11 +88,11 @@ def expression(ctx: Context, inp: ourlang.Expression) -> ConstraintGenerator:
                 comment = f'The type of the value passed to argument {arg_no} of function {func_name} should match the type of that argument'
 
             if isinstance(sig_part, functions.TypeVariable):
-                yield SameTypeConstraint(type_var_map[sig_part], arg_expr.type3, comment=comment)
+                yield SameTypeConstraint(type_var_map[sig_part], arg_placeholders[arg_expr], comment=comment)
                 continue
 
             if isinstance(sig_part, type3types.Type3):
-                yield SameTypeConstraint(sig_part, arg_expr.type3, comment=comment)
+                yield SameTypeConstraint(sig_part, arg_placeholders[arg_expr], comment=comment)
                 continue
 
             raise NotImplementedError(sig_part)
@@ -94,11 +101,12 @@ def expression(ctx: Context, inp: ourlang.Expression) -> ConstraintGenerator:
     if isinstance(inp, ourlang.TupleInstantiation):
         r_type = []
         for arg in inp.elements:
-            yield from expression(ctx, arg)
+            arg_phft = PlaceholderForType([arg])
-            r_type.append(arg.type3)
+            yield from expression(ctx, arg, arg_phft)
+            r_type.append(arg_phft)
 
         yield TupleMatchConstraint(
-            inp.type3,
+            phft,
             r_type,
             comment='The type of a tuple is a combination of its members'
         )
@@ -106,10 +114,13 @@ def expression(ctx: Context, inp: ourlang.Expression) -> ConstraintGenerator:
         return
 
     if isinstance(inp, ourlang.Subscript):
-        yield from expression(ctx, inp.varref)
+        varref_phft = PlaceholderForType([inp.varref])
-        yield from expression(ctx, inp.index)
+        index_phft = PlaceholderForType([inp.index])
 
-        yield CanBeSubscriptedConstraint(inp.type3, inp.varref.type3, inp.index)
+        yield from expression(ctx, inp.varref, varref_phft)
+        yield from expression(ctx, inp.index, index_phft)
+
+        yield CanBeSubscriptedConstraint(phft, varref_phft, inp.index, index_phft)
         return
 
     if isinstance(inp, ourlang.AccessStructMember):
@@ -117,33 +128,40 @@ def expression(ctx: Context, inp: ourlang.Expression) -> ConstraintGenerator:
         st_args = prelude.struct.did_construct(inp.struct_type3)
         assert st_args is not None  # FIXME: See test_struct.py::test_struct_not_accessible
 
-        yield from expression(ctx, inp.varref)
+        yield from expression(ctx, inp.varref, PlaceholderForType([inp.varref]))  # TODO
-        yield SameTypeConstraint(st_args[inp.member], inp.type3,
+        yield SameTypeConstraint(st_args[inp.member], phft,
             comment=f'The type of a struct member reference is the same as the type of struct member {inp.struct_type3.name}.{inp.member}')
         return
 
     if isinstance(inp, ourlang.Fold):
-        yield from expression(ctx, inp.base)
+        base_phft = PlaceholderForType([inp.base])
-        yield from expression(ctx, inp.iter)
+        iter_phft = PlaceholderForType([inp.iter])
 
-        yield SameTypeConstraint(inp.func.posonlyargs[0].type3, inp.func.returns_type3, inp.base.type3, inp.type3,
+        yield from expression(ctx, inp.base, base_phft)
+        yield from expression(ctx, inp.iter, iter_phft)
+
+        yield SameTypeConstraint(inp.func.posonlyargs[0].type3, inp.func.returns_type3, base_phft, phft,
             comment='foldl :: Foldable t => (b -> a -> b) -> b -> t a -> b')
-        yield MustImplementTypeClassConstraint(ctx, 'Foldable', [inp.iter.type3])
+        yield MustImplementTypeClassConstraint(ctx, 'Foldable', [iter_phft])
 
         return
 
     raise NotImplementedError(expression, inp)
 
 def statement_return(ctx: Context, fun: ourlang.Function, inp: ourlang.StatementReturn) -> ConstraintGenerator:
-    yield from expression(ctx, inp.value)
+    phft = PlaceholderForType([inp.value])
 
-    yield SameTypeConstraint(fun.returns_type3, inp.value.type3,
+    yield from expression(ctx, inp.value, phft)
+
+    yield SameTypeConstraint(fun.returns_type3, phft,
         comment=f'The type of the value returned from function {fun.name} should match its return type')
 
 def statement_if(ctx: Context, fun: ourlang.Function, inp: ourlang.StatementIf) -> ConstraintGenerator:
-    yield from expression(ctx, inp.test)
+    test_phft = PlaceholderForType([inp.test])
 
-    yield SameTypeConstraint(inp.test.type3, prelude.bool_,
+    yield from expression(ctx, inp.test, test_phft)
+
+    yield SameTypeConstraint(test_phft, prelude.bool_,
         comment='Must pass a boolean expression to if')
 
     for stmt in inp.statements:
@@ -173,8 +191,10 @@ def function(ctx: Context, inp: ourlang.Function) -> ConstraintGenerator:
         yield from statement(ctx, inp, stmt)
 
 def module_constant_def(ctx: Context, inp: ourlang.ModuleConstantDef) -> ConstraintGenerator:
-    yield from constant(ctx, inp.constant)
+    phft = PlaceholderForType([inp.constant])
-    yield SameTypeConstraint(inp.type3, inp.constant.type3,
+
+    yield from constant(ctx, inp.constant, phft)
+    yield SameTypeConstraint(inp.type3, phft,
         comment=f'The type of the value for module constant definition {inp.name} should match the type of that constant')
 
 def module(ctx: Context, inp: ourlang.Module) -> ConstraintGenerator:

phasm/type3/entry.py

@@ -115,8 +115,6 @@ def phasm_type3(inp: ourlang.Module, verbose: bool = False) -> None:
     # FIXME: This doesn't work with e.g. `:: [a] -> a`, as the placeholder is inside a type
     for plh, typ in placeholder_substitutes.items():
         for expr in plh.update_on_substitution:
-            assert expr.type3 is plh
-
             expr.type3 = typ
 
 def print_constraint(placeholder_id_map: Dict[int, str], constraint: ConstraintBase) -> None:

phasm/type3/placeholders.py

@@ -14,7 +14,7 @@ class ExpressionProtocol(Protocol):
     A protocol for classes that should be updated on substitution
     """
 
-    type3: 'Type3OrPlaceholder'
+    type3: Type3 | None
     """
     The type to update
     """

tests/integration/test_lang/test_literals.py

@@ -6,7 +6,20 @@ from ..helpers import Suite
 
 
 @pytest.mark.integration_test
-def test_expr_constant_literal_does_not_fit():
+def test_expr_constant_literal_does_not_fit_module_constant():
+    code_py = """
+CONSTANT: u8 = 1000
+
+@exported
+def testEntry() -> u8:
+    return CONSTANT
+"""
+
+    with pytest.raises(Type3Exception, match=r'Must fit in 1 byte\(s\)'):
+        Suite(code_py).run_code()
+
+@pytest.mark.integration_test
+def test_expr_constant_literal_does_not_fit_return():
     code_py = """
 @exported
 def testEntry() -> u8: