diff --git a/agast.py b/agast.py
index 376ae3a..6ff1e03 100644
--- a/agast.py
+++ b/agast.py
@@ -1,11 +1,26 @@
 from typing import *
-from lark import Transformer, Tree
+from lark import Transformer, Tree, Token
 
-class Interface: pass
+T = TypeVar("T")
 
-class Node: pass
+class Decl:
+	name: str
+class Iface(Decl):
+	def __init__(self, name: str):
+		self.name = name
+class IfaceField: pass
+
+class IfaceRef: pass
+
+class Node(Decl):
+	ifaces: List[IfaceRef]
 
 class NodeRef: pass
+class NodeRefByName(NodeRef):
+	def __init__(self, name: str):
+		self.name = name
+	def __repr__(self) -> str: return f"NodeRefByName({self.name})"
+
 
 class Sym: pass
 class SymRename(Sym):
@@ -42,14 +57,33 @@ class ExprCall(Expr):
 		self.func = func
 		self.args = args
 	def __repr__(self) -> str: return f"{self.func}({self.args})"
+class ExprName(Expr):
+	def __init__(self, name: str):
+		self.name = name
+	def __repr__(self) -> str: return f"{self.name}"
+
+class Parser(Transformer[List[Decl]]):
+	def program(self, items: List[Decl]) -> List[Decl]: return items
+
+	def iface(self, items: List[Any]) -> Iface:
+		[name, fields] = items
+		return Iface(name)
+	def iface_field(self, items: List[str]) -> IfaceField:
+		[name, ty] = items
+		return IfaceField()
+
+	def node(self, items: List[Any]) -> Node:
+		return Node()
 
-class Parser(Transformer[None]):
 	def variant(self, items: List[Any]) -> Variant:
 		[prod, equations] = items
 		return Variant(prod, equations)
 	def prod(self, items: List[Sym]) -> List[Sym]: return items
+
 	def sym_rename(self, items: List[Any]) -> Sym: return SymRename(items[0], items[1])
 
+	def node_ref_name(self, items: List[str]) -> NodeRefByName: return NodeRefByName(items[0])
+
 	def expr_dot(self, items: List[Expr]) -> Expr:
 		[left, _, right] = items
 		return ExprDot(left, right)
@@ -62,3 +96,7 @@ class Parser(Transformer[None]):
 	def expr_call(self, items: List[Expr]) -> Expr:
 		[func, _, args, _] = items
 		return ExprMul(func, args)
+
+	def sep_trail(self, items: List[Tree]) -> List[T]:
+		return list(map(lambda it: cast(T, it), items))
+	def ident(self, items: List[Token]) -> str: return cast(str, items[0].value)
diff --git a/agtypeck.py b/agtypeck.py
new file mode 100644
index 0000000..24f2cc1
--- /dev/null
+++ b/agtypeck.py
@@ -0,0 +1,17 @@
+from typing import *
+from agast import *
+
+def typecheck(program: List[Decl]) -> None:
+	i = 0
+	def gen(name: str = "") -> str:
+		return f"__ag{i:03}{name}"
+
+	# collect a list of name -> iface declarations
+	ifaces: Dict[str, Decl] = dict(
+		map(lambda c: (c.name, c),
+		filter(lambda c: isinstance(c, Iface),
+			program)))
+	print(ifaces)
+
+	for node in filter(lambda c: isinstance(c, Node), program):
+		print(node)
diff --git a/gen.py b/gen.py
index b773ea2..ed33aa9 100644
--- a/gen.py
+++ b/gen.py
@@ -2,23 +2,34 @@ import textwrap
 import os
 from lark import Lark
 
-from agast import Parser, Interface
+from agast import *
+from agtypeck import *
 
-p = Lark(open("grammar.lark").read(), parser="lalr", transformer=Parser())
+p = Lark(open("grammar.lark").read(), start="program", parser="lalr")
 
 if __name__ == "__main__":
 	with open("arith.ag") as f:
 		data = f.read()
 
-	t = p.parse(data)
-	print(t)
+	cst = p.parse(data)
+	# print("cst", cst)
+
+	trans = Parser()
+	ast = trans.transform(cst)
+	print("ast", ast)
+
+	typecheck(ast)
+
+	parser_data = ""
 
 	if not os.path.exists("gen"):
 		os.makedirs("gen")
 	with open("gen/arith.py", "w") as f:
-		f.write(textwrap.dedent("""
+		f.write(textwrap.dedent(f"""
 			from typing import Generic, TypeVar
+			from lark import Lark
 			T = TypeVar('T')
 			class Thunk(Generic[T]):
 				pass
+			parser = Lark('''{parser_data}''')
 		"""))
diff --git a/grammar.lark b/grammar.lark
index 338fb44..4d02bbc 100644
--- a/grammar.lark
+++ b/grammar.lark
@@ -1,19 +1,22 @@
-start: decl*
+program: decl*
 
-decl: iface
+?decl: iface
 	| node
 
-iface: IFACE IDENT "{" iface_field (COMMA iface_field)? COMMA? "}"
-iface_field: IDENT COLON IDENT
+sep_trail{item, punc}: item (punc item)? punc?
 
-node: NODE IDENT COLON IDENT "{" variant* "}"
+iface: "iface" ident "{" sep_trail{iface_field, ","} "}"
+iface_field: ident ":" ident
+
+node: NODE ident ":" ident "{" variant* "}"
 variant: prod "=>" "{" equation_* "}"
 prod: sym*
 sym: sym_rename
 	| STRING
-sym_rename: "<" IDENT ":" node_ref ">"
-node_ref: IDENT
+sym_rename: "<" ident ":" node_ref ">"
+node_ref: node_ref_name
 	| STRING
+node_ref_name: ident
 equation_: equation SEMI
 equation: expr EQ expr
 
@@ -21,13 +24,15 @@ expr: expr_dot
 	| expr_add
 	| expr_mul
 	| expr_call
-	| IDENT
+	| expr_name
 expr_dot: expr DOT expr
 expr_add: expr ADD expr
 expr_mul: expr MUL expr
 expr_call: expr LPAR args RPAR
+expr_name: ident
 args: expr (COMMA expr)? COMMA?
 
+ident: IDENT
 IDENT: /([a-zA-Z][a-zA-Z0-9_]*)|(_[a-zA-Z0-9_]+)/
 IFACE: "iface"
 NODE: "node"
diff --git a/run.ps1 b/run.ps1
new file mode 100644
index 0000000..896b876
--- /dev/null
+++ b/run.ps1
@@ -0,0 +1,16 @@
+#blessed https://stackoverflow.com/a/52784160
+
+function Invoke-Call {
+    param (
+        [scriptblock]$ScriptBlock,
+        [string]$ErrorAction = $ErrorActionPreference
+    )
+    & @ScriptBlock
+    if (($lastexitcode -ne 0) -and $ErrorAction -eq "Stop") {
+        exit $lastexitcode
+    }
+}
+
+Invoke-Call -ScriptBlock {mypy (get-item *.py) } -ErrorAction Stop
+Invoke-Call -ScriptBlock {python gen.py } -ErrorAction Stop
+Invoke-Call -ScriptBlock {mypy (get-item gen/*.py) } -ErrorAction Stop
\ No newline at end of file
diff --git a/watch.ps1 b/watch.ps1
new file mode 100644
index 0000000..2bcc73f
--- /dev/null
+++ b/watch.ps1
@@ -0,0 +1 @@
+watchexec --shell=powershell -ce py -i gen './run.ps1'