Chore: Cleanup type checks

A lot of isinstance checks no longer did anything, since
the referred to variable was always a type.

In some places, we used it to check if a type was internal,
it's unclear if we will need to rebuild those checks in
the future.

phasm/codestyle.py

@@ -6,7 +6,6 @@ It's intented to be a "any color, as long as it's black" kind of renderer
 from typing import Generator
 
 from . import ourlang, prelude
-from .type3.placeholders import TYPE3_ASSERTION_ERROR, Type3OrPlaceholder
 from .type3.types import Type3
 
 
@@ -18,12 +17,10 @@ def phasm_render(inp: ourlang.Module) -> str:
 
 Statements = Generator[str, None, None]
 
-def type3(inp: Type3OrPlaceholder) -> str:
+def type3(inp: Type3) -> str:
     """
     Render: type's name
     """
-    assert isinstance(inp, Type3), TYPE3_ASSERTION_ERROR
-
     if inp is prelude.none:
         return 'None'
 

phasm/compiler.py

@@ -9,11 +9,12 @@ from .runtime import calculate_alloc_size, calculate_member_offset
 from .stdlib import alloc as stdlib_alloc
 from .stdlib import types as stdlib_types
 from .type3 import functions as type3functions
-from .type3 import placeholders as type3placeholders
 from .type3 import typeclasses as type3classes
 from .type3 import types as type3types
 from .wasmgenerator import Generator as WasmGenerator
 
+TYPE3_ASSERTION_ERROR = 'You must call phasm_type3 after calling phasm_parse before your program can be compiled'
+
 LOAD_STORE_TYPE_MAP = {
     'i8': 'i32', # Have to use an u32, since there is no native i8 type
     'u8': 'i32', # Have to use an u32, since there is no native u8 type
@@ -268,14 +269,14 @@ def phasm_compile(inp: ourlang.Module) -> wasm.Module:
     """
     return module(inp)
 
-def type3(inp: type3placeholders.Type3OrPlaceholder) -> wasm.WasmType:
+def type3(inp: type3types.Type3) -> wasm.WasmType:
     """
     Compile: type
 
     Types are used for example in WebAssembly function parameters
     and return types.
     """
-    assert isinstance(inp, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+    assert inp is not None, TYPE3_ASSERTION_ERROR
 
     if inp == prelude.none:
         return wasm.WasmTypeNone()
@@ -327,7 +328,7 @@ def tuple_instantiation(wgn: WasmGenerator, inp: ourlang.TupleInstantiation) ->
     """
     Compile: Instantiation (allocation) of a tuple
     """
-    assert isinstance(inp.type3, type3types.Type3)
+    assert inp.type3 is not None, TYPE3_ASSERTION_ERROR
 
     args: list[type3types.Type3] = []
 
@@ -345,7 +346,7 @@ def tuple_instantiation(wgn: WasmGenerator, inp: ourlang.TupleInstantiation) ->
 
     comment_elements = ''
     for element in inp.elements:
-        assert isinstance(element.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+        assert element.type3 is not None, TYPE3_ASSERTION_ERROR
         comment_elements += f'{element.type3.name}, '
 
     tmp_var = wgn.temp_var_i32('tuple_adr')
@@ -359,17 +360,11 @@ def tuple_instantiation(wgn: WasmGenerator, inp: ourlang.TupleInstantiation) ->
     # Store each element individually
     offset = 0
     for element, exp_type3 in zip(inp.elements, args, strict=True):
-        if isinstance(exp_type3, type3placeholders.PlaceholderForType):
-            assert exp_type3.resolve_as is not None
-            assert isinstance(exp_type3.resolve_as, type3types.Type3)
-            exp_type3 = exp_type3.resolve_as
-
         assert element.type3 == exp_type3
 
         if (prelude.InternalPassAsPointer, (exp_type3, )) in prelude.PRELUDE_TYPE_CLASS_INSTANCES_EXISTING:
             mtyp = 'i32'
         else:
-            assert isinstance(exp_type3, type3types.Type3), NotImplementedError('Tuple of applied types / structs')
             mtyp = LOAD_STORE_TYPE_MAP[exp_type3.name]
 
         wgn.add_statement('nop', comment='PRE')
@@ -392,7 +387,7 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
         raise Exception
 
     if isinstance(inp, ourlang.ConstantPrimitive):
-        assert isinstance(inp.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+        assert inp.type3 is not None, TYPE3_ASSERTION_ERROR
 
         if inp.type3 in (prelude.i8, prelude.u8, ):
             # No native u8 type - treat as i32, with caution
@@ -433,7 +428,7 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
             return
 
         if isinstance(inp.variable, ourlang.ModuleConstantDef):
-            assert isinstance(inp.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+            assert inp.type3 is not None, TYPE3_ASSERTION_ERROR
 
             if (prelude.InternalPassAsPointer, (inp.type3, )) in prelude.PRELUDE_TYPE_CLASS_INSTANCES_EXISTING:
                 assert isinstance(inp.variable.constant, (ourlang.ConstantBytes, ourlang.ConstantStruct, ourlang.ConstantTuple, ))
@@ -443,11 +438,8 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
                 wgn.i32.const(address)
                 return
 
-            if isinstance(inp.type3, type3types.Type3):
-                expression(wgn, inp.variable.constant)
-                return
-
-            raise NotImplementedError(expression, inp)
+            expression(wgn, inp.variable.constant)
+            return
 
         raise NotImplementedError(expression, inp.variable)
 
@@ -455,7 +447,7 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
         expression(wgn, inp.left)
         expression(wgn, inp.right)
 
-        assert isinstance(inp.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+        assert inp.type3 is not None, TYPE3_ASSERTION_ERROR
 
         type_var_map: Dict[type3functions.TypeVariable, type3types.Type3] = {}
 
@@ -464,7 +456,7 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
                 # Fixed type, not part of the lookup requirements
                 continue
 
-            assert isinstance(arg_expr.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+            assert arg_expr.type3 is not None, TYPE3_ASSERTION_ERROR
             type_var_map[type_var] = arg_expr.type3
 
         instance_key = ','.join(
@@ -492,7 +484,7 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
                     # Fixed type, not part of the lookup requirements
                     continue
 
-                assert isinstance(arg_expr.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+                assert arg_expr.type3 is not None, TYPE3_ASSERTION_ERROR
                 type_var_map[type_var] = arg_expr.type3
 
             instance_key = ','.join(
@@ -515,7 +507,7 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
         return
 
     if isinstance(inp, ourlang.Subscript):
-        assert isinstance(inp.varref.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+        assert inp.varref.type3 is not None, TYPE3_ASSERTION_ERROR
 
         if inp.varref.type3 is prelude.bytes_:
             expression(wgn, inp.varref)
@@ -523,7 +515,7 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
             wgn.call(stdlib_types.__subscript_bytes__)
             return
 
-        assert isinstance(inp.varref.type3, type3types.Type3)
+        assert inp.varref.type3 is not None, TYPE3_ASSERTION_ERROR
 
         sa_args = prelude.static_array.did_construct(inp.varref.type3)
         if sa_args is not None:
@@ -549,7 +541,6 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
                 wgn.i32.mul()
                 wgn.i32.add()
 
-                assert isinstance(el_type, type3types.Type3), NotImplementedError('Tuple of applied types / structs')
                 mtyp = LOAD_STORE_TYPE_MAP[el_type.name]
 
                 wgn.add_statement(f'{mtyp}.load')
@@ -562,18 +553,17 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
 
                 offset = 0
                 for el_type in tp_args[0:inp.index.value]:
-                    assert isinstance(el_type, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+                    assert el_type is not None, TYPE3_ASSERTION_ERROR
                     offset += calculate_alloc_size(el_type)
 
                 el_type = tp_args[inp.index.value]
-                assert isinstance(el_type, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+                assert el_type is not None, TYPE3_ASSERTION_ERROR
 
                 expression(wgn, inp.varref)
 
                 if (prelude.InternalPassAsPointer, (el_type, )) in prelude.PRELUDE_TYPE_CLASS_INSTANCES_EXISTING:
                     mtyp = 'i32'
                 else:
-                    assert isinstance(el_type, type3types.Type3), NotImplementedError('Tuple of applied types / structs')
                     mtyp = LOAD_STORE_TYPE_MAP[el_type.name]
 
                 wgn.add_statement(f'{mtyp}.load', f'offset={offset}')
@@ -582,14 +572,13 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
         raise NotImplementedError(expression, inp, inp.varref.type3)
 
     if isinstance(inp, ourlang.AccessStructMember):
-        assert isinstance(inp.struct_type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+        assert inp.struct_type3 is not None, TYPE3_ASSERTION_ERROR
 
         st_args = prelude.struct.did_construct(inp.struct_type3)
         assert st_args is not None
 
         member_type = st_args[inp.member]
 
-        assert isinstance(member_type, type3types.Type3), NotImplementedError('Tuple of applied types / structs')
         mtyp = LOAD_STORE_TYPE_MAP[member_type.name]
 
         expression(wgn, inp.varref)
@@ -608,7 +597,7 @@ def expression_fold(wgn: WasmGenerator, inp: ourlang.Fold) -> None:
     """
     Compile: Fold expression
     """
-    assert isinstance(inp.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+    assert inp.type3 is not None, TYPE3_ASSERTION_ERROR
 
     if inp.iter.type3 is not prelude.bytes_:
         raise NotImplementedError(expression_fold, inp, inp.iter.type3)
@@ -839,7 +828,7 @@ def module_data(inp: ourlang.ModuleData) -> bytes:
         data_list: List[bytes] = []
 
         for constant in block.data:
-            assert isinstance(constant.type3, type3types.Type3), (id(constant), type3placeholders.TYPE3_ASSERTION_ERROR)
+            assert constant.type3 is not None, TYPE3_ASSERTION_ERROR
 
             if isinstance(constant, ourlang.ConstantMemoryStored) and block is not constant.data_block:
                 # It's stored in a different block

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/parser.py

@@ -163,8 +163,8 @@ class OurVisitor:
 
             arg_type = self.visit_type(module, arg.annotation)
 
-            # if isisntance(arg_type, TypeVariable):
-            #   arg_type = PlaceHolderForType()
+            # FIXME: Allow TypeVariable in the function signature
+            # This would also require FunctionParam to accept a placeholder
 
             function.signature.args.append(arg_type)
             function.posonlyargs.append(FunctionParam(

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:
@@ -157,7 +158,7 @@ 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: placeholders.Type3OrPlaceholder, args: Iterable[placeholders.Type3OrPlaceholder], comment: str):
         super().__init__(comment=comment)
 
         self.exp_type = exp_type
@@ -348,8 +349,12 @@ 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 +376,12 @@ 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 +405,12 @@ 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)
             )
 
@@ -421,20 +434,27 @@ 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
     type3: placeholders.Type3OrPlaceholder
     index: ourlang.Expression
-    index_type3: placeholders.Type3OrPlaceholder
+    index_phft: placeholders.Type3OrPlaceholder
 
-    def __init__(self, ret_type3: placeholders.Type3OrPlaceholder, type3: placeholders.Type3OrPlaceholder, index: ourlang.Expression, comment: Optional[str] = None) -> None:
+    def __init__(
+            self,
+            ret_type3: placeholders.PlaceholderForType,
+            type3: placeholders.PlaceholderForType,
+            index: ourlang.Expression,
+            index_phft: placeholders.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
@@ -451,7 +471,7 @@ 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 +498,13 @@ 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:
-            yield from expression(ctx, call_arg)
+        arg_placeholders = {
+            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)
-            r_type.append(arg.type3)
+            arg_phft = PlaceholderForType([arg])
+            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)
-        yield from expression(ctx, inp.index)
+        varref_phft = PlaceholderForType([inp.varref])
+        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 SameTypeConstraint(st_args[inp.member], inp.type3,
+        yield from expression(ctx, inp.varref, PlaceholderForType([inp.varref]))  # TODO
+        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)
-        yield from expression(ctx, inp.iter)
+        base_phft = PlaceholderForType([inp.base])
+        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)
-    yield SameTypeConstraint(inp.type3, inp.constant.type3,
+    phft = PlaceholderForType([inp.constant])
+
+    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

@@ -7,14 +7,13 @@ from typing import Any, Iterable, List, Optional, Protocol, Union
 
 from .types import Type3
 
-TYPE3_ASSERTION_ERROR = 'You must call phasm_type3 after calling phasm_parse before you can call any other method'
 
 class ExpressionProtocol(Protocol):
     """
     A protocol for classes that should be updated on substitution
     """
 
-    type3: 'Type3OrPlaceholder'
+    type3: Type3 | None
     """
     The type to update
     """

tests/integration/helpers.py

@@ -5,7 +5,6 @@ from typing import Any, Generator, Iterable, List, TextIO, Union
 from phasm import compiler, prelude
 from phasm.codestyle import phasm_render
 from phasm.runtime import calculate_alloc_size
-from phasm.type3 import placeholders as type3placeholders
 from phasm.type3 import types as type3types
 
 from . import runners
@@ -65,9 +64,6 @@ class Suite:
             runner.interpreter_dump_memory(sys.stderr)
 
             for arg, arg_typ in zip(args, func_args, strict=True):
-                assert not isinstance(arg_typ, type3placeholders.PlaceholderForType), \
-                    'Cannot call polymorphic function from outside'
-
                 if arg_typ in (prelude.u8, prelude.u32, prelude.u64, ):
                     assert isinstance(arg, int)
                     wasm_args.append(arg)
@@ -88,7 +84,6 @@ class Suite:
                     wasm_args.append(adr)
                     continue
 
-                assert isinstance(arg_typ, type3types.Type3)
                 sa_args = prelude.static_array.did_construct(arg_typ)
                 if sa_args is not None:
                         adr = _allocate_memory_stored_value(runner, arg_typ, arg)
@@ -222,8 +217,6 @@ def _allocate_memory_stored_value(
 
             offset = adr
             for val_el_val, val_el_typ in zip(val, tp_args, strict=True):
-                assert not isinstance(val_el_typ, type3placeholders.PlaceholderForType)
-
                 offset += _write_memory_stored_value(runner, offset, val_el_typ, val_el_val)
             return adr
 
@@ -240,8 +233,6 @@ def _allocate_memory_stored_value(
 
         offset = adr
         for val_el_name, val_el_typ in st_args.items():
-            assert not isinstance(val_el_typ, type3placeholders.PlaceholderForType)
-
             val_el_val = val[val_el_name]
             offset += _write_memory_stored_value(runner, offset, val_el_typ, val_el_val)
         return adr
@@ -299,8 +290,6 @@ def _load_memory_stored_returned_value(
 
         return _load_bytes_from_address(runner, ret_type3, wasm_value)
 
-    assert isinstance(ret_type3, type3types.Type3) # Type hint
-
     sa_args = prelude.static_array.did_construct(ret_type3)
     if sa_args is not None:
             assert isinstance(wasm_value, int), wasm_value
@@ -366,8 +355,6 @@ def _unpack(runner: runners.RunnerBase, typ: type3types.Type3, inp: bytes) -> An
         assert len(inp) == 4
         adr = struct.unpack('<I', inp)[0]
 
-        assert isinstance(typ, type3types.Type3)
-
         sa_args = prelude.static_array.did_construct(typ)
         if sa_args is not None:
             sa_type, sa_len = sa_args
@@ -404,9 +391,6 @@ def _split_read_bytes(all_bytes: bytes, split_sizes: Iterable[int]) -> Generator
 def _load_static_array_from_address(runner: runners.RunnerBase, sub_typ: type3types.Type3, len_typ: type3types.IntType3, adr: int) -> Any:
     sys.stderr.write(f'Reading 0x{adr:08x} {sub_typ:s} {len_typ:s}\n')
 
-    assert not isinstance(sub_typ, type3placeholders.PlaceholderForType)
-    assert isinstance(len_typ, type3types.IntType3)
-
     sa_len = len_typ.value
 
     arg_size_1 = calculate_alloc_size(sub_typ, is_member=True)

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: