From 0d34326d71cb5dda4814076cee733ced7dd43958 Mon Sep 17 00:00:00 2001
From: Hisham Muhammad <hisham@gobolinux.org>
Date: Fri, 25 Oct 2024 15:59:09 -0300
Subject: [PATCH] fix: type variables from returns resolve for arguments

Fixes #838.
---
 spec/lang/inference/function_call_spec.lua   | 70 ++++++++++++++++++++
 spec/lang/inference/function_result_spec.lua | 19 ------
 spec/lang/statement/forin_spec.lua           |  2 +-
 tl.lua                                       |  4 +-
 tl.tl                                        |  4 +-
 5 files changed, 75 insertions(+), 24 deletions(-)
 create mode 100644 spec/lang/inference/function_call_spec.lua
 delete mode 100644 spec/lang/inference/function_result_spec.lua

diff --git a/spec/lang/inference/function_call_spec.lua b/spec/lang/inference/function_call_spec.lua
new file mode 100644
index 000000000..c9758bcde
--- /dev/null
+++ b/spec/lang/inference/function_call_spec.lua
@@ -0,0 +1,70 @@
+local util = require("spec.util")
+
+describe("function call", function()
+   describe("results", function()
+      it("should be adjusted down to 1 result in an expression list", util.check([[
+         local function f(): string, number
+         end
+         local a, b = f(), "hi"
+         a = "hey"
+      ]]))
+
+      it("can resolve type arguments based on expected type at use site (#512)", util.check([[
+         local function get_foos<T>():{T}
+            return {}
+         end
+
+         local foos:{integer} = get_foos()
+         print(foos)
+      ]]))
+   end)
+
+   describe("arguments", function()
+      it("type variables from returns resolve for arguments (regression test for #838)", util.check([[
+         local fcts: {integer:function(val: any, opt?: string): any}
+
+         local function bar (val: number): number
+            print(val)
+            return val
+         end
+
+         local function bar2 (val: number, val2: string): number
+            print(val, val2)
+            return val
+         end
+
+         fcts = {  -- OK, with table constructor
+            [11] = function (val: string): string
+               print(val)
+               return val
+            end,
+            [12] = function (val: string, val2: string): string
+               print(val, val2)
+               return val
+            end,
+            [21] = bar,
+            [22] = bar2,
+         }
+         setmetatable(fcts, {
+            __tostring = function(): string return 'fcts' end
+         })
+
+         fcts = setmetatable({  -- Ok, as an argument via type variable
+            [11] = function (val: string): string
+               print(val)
+               return val
+            end,
+            [12] = function (val: string, val2: string): string
+               print(val, val2)
+               return val
+            end,
+            [21] = bar,
+            [22] = bar2,
+         }, {
+            __tostring = function(): string return 'fcts' end
+         })
+
+         print(fcts)
+      ]]))
+   end)
+end)
diff --git a/spec/lang/inference/function_result_spec.lua b/spec/lang/inference/function_result_spec.lua
deleted file mode 100644
index 96891cbeb..000000000
--- a/spec/lang/inference/function_result_spec.lua
+++ /dev/null
@@ -1,19 +0,0 @@
-local util = require("spec.util")
-
-describe("function results", function()
-   it("should be adjusted down to 1 result in an expression list", util.check([[
-      local function f(): string, number
-      end
-      local a, b = f(), "hi"
-      a = "hey"
-   ]]))
-
-   it("can resolve type arguments based on expected type at use site (#512)", util.check([[
-      local function get_foos<T>():{T}
-         return {}
-      end
-
-      local foos:{integer} = get_foos()
-      print(foos)
-   ]]))
-end)
diff --git a/spec/lang/statement/forin_spec.lua b/spec/lang/statement/forin_spec.lua
index 3a5916404..327068e85 100644
--- a/spec/lang/statement/forin_spec.lua
+++ b/spec/lang/statement/forin_spec.lua
@@ -96,7 +96,7 @@ describe("forin", function()
    it("with a callable record iterator", util.check([[
       local record R
          incr: integer
-         metamethod __call: function(): integer
+         metamethod __call: function(self): integer
       end
 
       local function foo(incr: integer): R
diff --git a/tl.lua b/tl.lua
index 93c69f3d8..ec3321984 100644
--- a/tl.lua
+++ b/tl.lua
@@ -12267,13 +12267,13 @@ self:expand_type(node, values, elements) })
                   for _, typ in ipairs(e1args) do
                      at = at + 1
                      if node.e2[at] then
-                        node.e2[at].expected = typ
+                        node.e2[at].expected = self:infer_at(node.e2[at], typ)
                      end
                   end
                   if e1type.args.is_va then
                      local typ = e1args[#e1args]
                      for i = at + 1, #node.e2 do
-                        node.e2[i].expected = typ
+                        node.e2[i].expected = self:infer_at(node.e2[i], typ)
                      end
                   end
                end
diff --git a/tl.tl b/tl.tl
index c894a74d6..af2e01ff5 100644
--- a/tl.tl
+++ b/tl.tl
@@ -12267,13 +12267,13 @@ do
                   for _, typ in ipairs(e1args) do
                      at = at + 1
                      if node.e2[at] then
-                        node.e2[at].expected = typ
+                        node.e2[at].expected = self:infer_at(node.e2[at], typ)
                      end
                   end
                   if e1type.args.is_va then
                      local typ = e1args[#e1args]
                      for i = at + 1, #node.e2 do
-                        node.e2[i].expected = typ
+                        node.e2[i].expected = self:infer_at(node.e2[i], typ)
                      end
                   end
                end