RFC: If statement initializers

docs/syntax-if-statements-initializers.md

@@ -6,13 +6,13 @@ Introduce an initializer expression that declares and initializes variables in i
 
 # Motivation
 
-Initializers can improve code clarity and reduce scope pollution by allowing developers to declare variables in the conditions of if statements. ⁤⁤ Declaring variables at the point of use in if statements for the scope of the if statement's block simplifies code, leading to better readability and understanding of program logic. By limiting the scope of variables to the condition's pertaining block, the risk of unintended variable reuse and naming conflicts is reduced. ⁤
+Initializers can improve code clarity and reduce scope pollution by allowing developers to declare variables in the conditions of if statements. ⁤⁤ Declaring variables at the point of use in if statements for the scope of the if statement's blocks simplifies code, leading to better readability and understanding of program logic. By limiting the scope of variables to the if statement's blocks, the risk of unintended variable reuse and naming conflicts is reduced. ⁤
 
 The reduced scope pollution improves register space in extreme cases (or auto-generated code) where developers have many variables defined and have to work around register limits by reducing the register size. In some scenarios, especially on Roblox, initializing variables within if statements can lead to improved performance and reduced complexity by avoiding unnecessary calls by developers. ⁤ A common paradigm used by Roblox developers is to use `Instance:FindFirstChild` in their condition and then access it afterwards instead of keeping an existing variable around in the new scope, polluting the existing scope.
 
 # Design
 
-If statements with initializers must match (following the Luau grammar) `'if' 'local' bindinglist ['=' explist] 'then'` and `'local' bindinglist ['=' explist] where exp 'then'` syntax. The variables declared by the initializer are only available to the block of that condition and will be undefined to the `elseif` conditions and blocks as well as the `else` block; any code after the if statement won't have the variables defined either.
+If statements with initializers must match (following the Luau grammar) `'if' 'local' bindinglist ['=' explist] 'then'` and `'local' bindinglist ['=' explist] where exp 'then'` syntax. The variables declared by an initializer are only available to the if statement's blocks; any code after the if statement won't have the variables defined.
 
 In the former case, the value of the first declared variable will be checked.
 
@@ -24,13 +24,13 @@ local function foo()
 end
 
 if local b = foo() then
-   print(b)
+   print(b, "truthy block")
 else
-   print("false")
+   print(b, "falsy block")
 end
 ```
 
-`Output: true`
+`Output: true	truthy block`
 
 In the latter case, the `exp` condition is checked rather than the initializer.
 
@@ -42,15 +42,15 @@ local function foo()
 end
 
 if local b = foo() where b == false then
-   print(b)
+   print(b, "truthy block")
 else
-   print("true")
+   print(b, "falsy block")
 end
 ```
 
-`Output: true`
+`Output: true	falsy block`
 
-When declaring multiple values inside of a condition, all of the variables will be tested for truthiness.
+When declaring multiple values inside of an initializer, the `where` clause is required.
 
 Example:
 
@@ -59,7 +59,7 @@ local function foo()
     return true, false
 end
 
-if local a,b = foo() then
+if local a,b = foo() where a and b then
 else
     print'Hello World, from Luau!'
 end