Add `with` block desugaring

trans/transpiler/__init__.py

@@ -2,6 +2,7 @@
 import ast
 
 from transpiler.consts import MAPPINGS
+from transpiler.phases.desugar_with import DesugarWith
 #from transpiler.phases import initial_pytype
 from transpiler.phases.emit_cpp.file import FileVisitor
 from transpiler.phases.if_main import IfMainVisitor
@@ -12,6 +13,7 @@ from transpiler.phases.typing.scope import Scope
 def transpile(source):
     res = ast.parse(source, type_comments=True)
     #res = initial_pytype.run(source, res)
+    res = DesugarWith().visit(res)
     IfMainVisitor().visit(res)
     ScoperBlockVisitor().visit(res)
     #print(res.scope)

trans/transpiler/phases/desugar_with/__init__.py

+# coding: utf-8
+import ast
+
+from transpiler.phases.utils import PlainBlock
+
+
+def process(items: list[ast.withitem], body: list[ast.stmt]) -> PlainBlock:
+    first, *rest = items
+    val, name = first.context_expr, first.optional_vars
+    cm_name = ast.Name(id=f"cm_{hash(first)}")
+    res = [
+        ast.Assign(targets=[cm_name], value=val)
+    ]
+    enter_call = ast.Call(func=ast.Attribute(value=cm_name, attr="__enter__"), args=[], keywords=[])
+    if name:
+        res.append(ast.Assign(targets=[name], value=enter_call))
+    else:
+        res.append(ast.Expr(value=enter_call))
+    if rest:
+        res.append(process(rest, body))
+    else:
+        res.append(PlainBlock(body))
+    res.append(ast.Expr(value=ast.Call(func=ast.Attribute(value=cm_name, attr="__exit__"), args=[], keywords=[])))
+    return PlainBlock(res)
+
+
+class DesugarWith(ast.NodeTransformer):
+    def visit_With(self, node: ast.With):
+        return process(node.items, node.body)
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