From bdc1b265a62ce7bb8121ff619378266c1f7f1938 Mon Sep 17 00:00:00 2001
From: LordBaryhobal <lordbaryhobal@gmail.com>
Date: Thu, 18 Jun 2026 13:19:17 +0200
Subject: [PATCH] feat(gen): generate basic constraint assertion

---
 midas/generator/constraints.py | 92 ++++++++++++++++++++++++++++++++++
 midas/generator/generator.py   | 22 +++++++-
 2 files changed, 112 insertions(+), 2 deletions(-)
 create mode 100644 midas/generator/constraints.py

diff --git a/midas/generator/constraints.py b/midas/generator/constraints.py
new file mode 100644
index 0000000..329b79b
--- /dev/null
+++ b/midas/generator/constraints.py
@@ -0,0 +1,92 @@
+import ast
+
+import midas.ast.midas as m
+from midas.lexer.token import TokenType
+
+LOGICAL_OPERATORS: dict[TokenType, type[ast.boolop]] = {
+    TokenType.AND: ast.And,
+    # TokenType.OR: ast.Or,
+}
+
+BINARY_OPERATORS: dict[TokenType, type[ast.operator]] = {
+    # TokenType.PLUS: ast.Add,
+    TokenType.MINUS: ast.Sub,
+    TokenType.STAR: ast.Mult,
+    TokenType.SLASH: ast.Div,
+}
+
+UNARY_OPERATORS: dict[TokenType, type[ast.unaryop]] = {
+    # TokenType.PLUS: ast.UAdd,
+    TokenType.MINUS: ast.USub,
+}
+
+COMPARISON_OPERATORS: dict[TokenType, type[ast.cmpop]] = {
+    TokenType.GREATER: ast.Gt,
+    TokenType.GREATER_EQUAL: ast.GtE,
+    TokenType.LESS: ast.Lt,
+    TokenType.LESS_EQUAL: ast.LtE,
+    TokenType.EQUAL_EQUAL: ast.Eq,
+    TokenType.BANG_EQUAL: ast.NotEq,
+}
+
+
+class ConstraintGenerator(m.Expr.Visitor[ast.expr]):
+    def visit_logical_expr(self, expr: m.LogicalExpr) -> ast.expr:
+        return ast.BoolOp(
+            op=LOGICAL_OPERATORS[expr.operator.type](),
+            values=[
+                expr.left.accept(self),
+                expr.right.accept(self),
+            ],
+        )
+
+    def visit_binary_expr(self, expr: m.BinaryExpr) -> ast.expr:
+        op: TokenType = expr.operator.type
+        if op in BINARY_OPERATORS:
+            return ast.BinOp(
+                left=expr.left.accept(self),
+                op=BINARY_OPERATORS[op](),
+                right=expr.right.accept(self),
+            )
+        if op in COMPARISON_OPERATORS:
+            return ast.Compare(
+                left=expr.left.accept(self),
+                ops=[COMPARISON_OPERATORS[op]()],
+                comparators=[expr.right.accept(self)],
+            )
+        raise ValueError(f"Unexpected binary operator {op}")
+
+    def visit_unary_expr(self, expr: m.UnaryExpr) -> ast.expr:
+        return ast.UnaryOp(
+            op=UNARY_OPERATORS[expr.operator.type](),
+            operand=expr.right.accept(self),
+        )
+
+    def visit_call_expr(self, expr: m.CallExpr) -> ast.expr:
+        return ast.Call(
+            func=expr.callee.accept(self),
+            args=[arg.accept(self) for arg in expr.arguments],
+            keywords=[
+                ast.keyword(arg=name, value=arg.accept(self))
+                for name, arg in expr.keywords.items()
+            ],
+        )
+
+    def visit_get_expr(self, expr: m.GetExpr) -> ast.expr:
+        return ast.Attribute(
+            value=expr.expr.accept(self),
+            attr=expr.name.lexeme,
+        )
+
+    def visit_variable_expr(self, expr: m.VariableExpr) -> ast.expr:
+        # TODO: lookup predicate
+        return ast.Name(id=expr.name.lexeme)
+
+    def visit_grouping_expr(self, expr: m.GroupingExpr) -> ast.expr:
+        return expr.accept(self)
+
+    def visit_literal_expr(self, expr: m.LiteralExpr) -> ast.expr:
+        return ast.Constant(value=expr.value)
+
+    def visit_wildcard_expr(self, expr: m.WildcardExpr) -> ast.expr:
+        return ast.Name(id="_")
diff --git a/midas/generator/generator.py b/midas/generator/generator.py
index 67e11e9..64c8c16 100644
--- a/midas/generator/generator.py
+++ b/midas/generator/generator.py
@@ -7,6 +7,7 @@ from typing import Optional, assert_never
 import midas.ast.midas as m
 import midas.ast.python as p
 from midas.ast.location import Location
+from midas.ast.printer import MidasPrinter
 from midas.checker.types import (
     AliasType,
     AppliedType,
@@ -23,6 +24,7 @@ from midas.checker.types import (
     UnitType,
     UnknownType,
 )
+from midas.generator.constraints import ConstraintGenerator
 from midas.utils import TypedAST
 
 
@@ -48,6 +50,8 @@ class Generator(p.Stmt.Visitor[ast.stmt], p.Expr.Visitor[ast.expr]):
         self._alias_count: int = 0
         self._scopes: list[Scope] = []
 
+        self._constraint_generator: ConstraintGenerator = ConstraintGenerator()
+
     def generate_ast(self, typed_ast: TypedAST, src_path: Path) -> ast.AST:
         self.rel_src_path = src_path.relative_to(self.workdir)
         self._typed_ast = typed_ast
@@ -357,5 +361,19 @@ class Generator(p.Stmt.Visitor[ast.stmt], p.Expr.Visitor[ast.expr]):
     def _make_constraint_assert(
         self, src_location: Location, expr: ast.expr, constraint: m.Expr
     ):
-        # TODO
-        pass
+        test: ast.expr = constraint.accept(self._constraint_generator)
+        self._add_assert(
+            test,
+            self._make_constraint_assert_message(src_location, expr, constraint),
+        )
+
+    def _make_constraint_assert_message(
+        self, location: Location, expr: ast.expr, constraint: m.Expr
+    ) -> ast.expr:
+        printer = MidasPrinter()
+        constraint_str: str = printer.print(constraint)
+        loc_str: str = f"{self.rel_src_path}:L{location.lineno}:{location.col_offset+1}"
+        # f"file.py:L1:1: ConstraintError: Value does not fit constraint 'v > 0'"
+        return ast.Constant(
+            f"{loc_str}: ConstraintError: Value does not fit constraint '{constraint_str}'"
+        )