From 8e276e494cb866914a66d8df862fdc64d780ce82 Mon Sep 17 00:00:00 2001
From: Hisham Muhammad <hisham@gobolinux.org>
Date: Wed, 22 Jan 2025 08:02:46 +0100
Subject: [PATCH] fix: ensure poly types rollback stack is consistent

Fixes #915.
---
 spec/api/get_types_spec.lua | 14 ++++++++++++--
 tl.lua                      |  6 +++---
 tl.tl                       |  6 +++---
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/spec/api/get_types_spec.lua b/spec/api/get_types_spec.lua
index 8239ac1f..33fc0bfb 100644
--- a/spec/api/get_types_spec.lua
+++ b/spec/api/get_types_spec.lua
@@ -22,16 +22,26 @@ describe("tl.get_types", function()
          local record R
             f: function(string)
             f: function(integer)
+
+            g: function<X>(string, X): {X}
+            g: function<T>(integer, T): T
          end
 
          R.f("hello")
+         R.f(9)
+         local z = R.g(123, "hello")
       ]], env))
 
       local tr, trenv = tl.get_types(result)
-      local y = 6
+      local y = 9
       local x = 11
       local type_at_y_x = tr.by_pos[""][y][x]
-      assert(tr.types[type_at_y_x].str == "function(string)")
+      assert.same(tr.types[type_at_y_x].str, "function(string)")
+
+      y = 11
+      x = 21
+      type_at_y_x = tr.by_pos[""][y][x]
+      assert.same(tr.types[type_at_y_x].str, "function(integer, T): T")
    end)
 
    it("reports record functions in record field list", function()
diff --git a/tl.lua b/tl.lua
index 757af8c5..adeede21 100644
--- a/tl.lua
+++ b/tl.lua
@@ -8222,8 +8222,8 @@ do
       end
    end
 
-   function TypeChecker:begin_scope_transaction()
-      self:begin_scope()
+   function TypeChecker:begin_scope_transaction(node)
+      self:begin_scope(node)
       local st = self.st
       st[#st].is_transaction = true
    end
@@ -10003,7 +10003,7 @@ a.types[i], b.types[i]), }
             expected_rets = a_type(node, "tuple", { tuple = { node.expected } })
          end
 
-         self:begin_scope_transaction()
+         self:begin_scope_transaction(node)
 
          local g
          local typeargs
diff --git a/tl.tl b/tl.tl
index 3d5827c1..8a1b046f 100644
--- a/tl.tl
+++ b/tl.tl
@@ -8222,8 +8222,8 @@ do
       end
    end
 
-   function TypeChecker:begin_scope_transaction()
-      self:begin_scope()
+   function TypeChecker:begin_scope_transaction(node: Node)
+      self:begin_scope(node)
       local st = self.st
       st[#st].is_transaction = true
    end
@@ -10003,7 +10003,7 @@ do
             expected_rets = a_tuple(node, { node.expected })
          end
 
-         self:begin_scope_transaction()
+         self:begin_scope_transaction(node)
 
          local g: GenericType
          local typeargs: {TypeArgType}