accept 'or' as a boolean in if/while/repeat expressions

Author: hishamhm

spec/statement/if_spec.lua

@@ -16,6 +16,15 @@ describe("if", function()
       end
    ]]))
 
+   it("if expression propagates a boolean context", util.check([[
+      local n = 123
+      local s = "hello"
+      if n or s then
+         local ns: number | string = n or s
+         print(ns)
+      end
+   ]]))
+
    it("accepts boolean expressions", util.check([[
       local s = "Hallo, Welt"
       if string.match(s, "world") or s == "Hallo, Welt" then

spec/statement/repeat_spec.lua

@@ -1,6 +1,29 @@
 local util = require("spec.util")
 
 describe("repeat", function()
+   it("accepts a boolean", util.check([[
+      local b = true
+      repeat
+         print(b)
+      until b
+   ]]))
+
+   it("accepts a non-boolean", util.check([[
+      local n = 123
+      repeat
+         print(n)
+      until n
+   ]]))
+
+   it("until expression propagates a boolean context", util.check([[
+      local n = 123
+      local s = "hello"
+      repeat
+         local ns: number | string = n or s
+         print(ns)
+      until n or s
+   ]]))
+
    it("only closes scope after until", util.check([[
       repeat
          local type R = record

spec/statement/while_spec.lua

@@ -0,0 +1,26 @@
+local util = require("spec.util")
+
+describe("while", function()
+   it("accepts a boolean", util.check([[
+      local b = true
+      while b do
+         print(b)
+      end
+   ]]))
+
+   it("accepts a non-boolean", util.check([[
+      local n = 123
+      while n do
+         print(n)
+      end
+   ]]))
+
+   it("while expression propagates a boolean context", util.check([[
+      local n = 123
+      local s = "hello"
+      while n or s do
+         local ns: number | string = n or s
+         print(ns)
+      end
+   ]]))
+end)

tl.lua

@@ -10764,6 +10764,9 @@ self:expand_type(node, values, elements) })
             if node.if_block_n > 1 then
                self:infer_negation_of_if_blocks(node, node.if_parent, node.if_block_n - 1)
             end
+            if node.exp then
+               node.exp.expected = a_type(node, "boolean", {})
+            end
          end,
          before_statements = function(self, node)
             if node.exp then
@@ -10784,6 +10787,7 @@ self:expand_type(node, values, elements) })
          before = function(self, node)
 
             self:widen_all_unions(node)
+            node.exp.expected = a_type(node, "boolean", {})
          end,
          before_statements = function(self, node)
             self:begin_scope(node)
@@ -10847,6 +10851,7 @@ self:expand_type(node, values, elements) })
          before = function(self, node)
 
             self:widen_all_unions(node)
+            node.exp.expected = a_type(node, "boolean", {})
          end,
 
          after = end_scope_and_none_type,
@@ -11707,6 +11712,10 @@ self:expand_type(node, values, elements) })
                      end
                      t = drop_constant_value(t)
                   end
+
+                  if expected and expected.typename == "boolean" then
+                     t = a_type(node, "boolean", {})
+                  end
                end
 
                if t then

tl.tl

@@ -10764,6 +10764,9 @@ do
             if node.if_block_n > 1 then
                self:infer_negation_of_if_blocks(node, node.if_parent, node.if_block_n - 1)
             end
+            if node.exp then
+               node.exp.expected = a_type(node, "boolean", {})
+            end
          end,
          before_statements = function(self: TypeChecker, node: Node)
             if node.exp then
@@ -10784,6 +10787,7 @@ do
          before = function(self: TypeChecker, node: Node)
             -- widen all narrowed variables because we don't calculate a fixpoint yet
             self:widen_all_unions(node)
+            node.exp.expected = a_type(node, "boolean", {})
          end,
          before_statements = function(self: TypeChecker, node: Node)
             self:begin_scope(node)
@@ -10847,6 +10851,7 @@ do
          before = function(self: TypeChecker, node: Node)
             -- widen all narrowed variables because we don't calculate a fixpoint yet
             self:widen_all_unions(node)
+            node.exp.expected = a_type(node, "boolean", {})
          end,
          -- only end scope after checking `until`, `statements` in repeat body has is_repeat == true
          after = end_scope_and_none_type,
@@ -11707,6 +11712,10 @@ do
                      end
                      t = drop_constant_value(t)
                   end
+
+                  if expected and expected is BooleanType then
+                     t = a_type(node, "boolean", {})
+                  end
                end
 
                if t then