avoid "got foo, expected foo" errors

Do not produce a confusing message when reporting on incompatible types with
the same local names. Before this commit, the included test case would produce
an error message saying "got X | integer, expected X | integer"; which was
technically correct because it referred to different nested records called X,
but it was confusing. Since we don't "resolve path names" based on the
position of the error, bailing out with a generic error message is better than
producing a confusing one.

spec/lang/assignment/to_union_spec.lua

@@ -75,4 +75,24 @@ describe("assignment to union", function()
       local x: {string | Item} = {"name1", {name="myname"}}
    ]]))
 
+   it("do not produce a confusing message when reporting on incompatible types with the same local names", util.check_type_error([[
+      local record A
+         record X
+         end
+
+         f: function(X | integer)
+      end
+
+      local record B
+         record X
+         end
+
+         g: function(): X | integer
+      end
+
+      A.f(B.g())
+   ]], {
+      { msg = "argument 1: types are incompatible" }
+   }))
+
 end)

tl.lua

@@ -9621,7 +9621,16 @@ a.types[i], b.types[i]), }
       end
 
       if (not ok) and not err then
-         return false, { Err("got %s, expected %s", t1, t2) }
+         if t1.typename == "invalid" or t2.typename == "invalid" then
+            return false, {}
+         end
+         local show_t1 = show_type(t1)
+         local show_t2 = show_type(t2)
+         if show_t1 == show_t2 then
+            return false, { Err_at(t1, "types are incompatible") }
+         else
+            return false, { Err_at(t1, "got " .. show_t1 .. ", expected " .. show_t2) }
+         end
       end
       return ok, err
    end

tl.tl

@@ -9621,7 +9621,16 @@ do
       end
 
       if (not ok) and not err then
-         return false, { Err("got %s, expected %s", t1, t2) }
+         if t1 is InvalidType or t2 is InvalidType then
+            return false, {}
+         end
+         local show_t1 = show_type(t1)
+         local show_t2 = show_type(t2)
+         if show_t1 == show_t2 then
+            return false, { Err_at(t1, "types are incompatible") }
+         else
+            return false, { Err_at(t1, "got " .. show_t1 .. ", expected " .. show_t2) }
+         end
       end
       return ok, err
    end