Fixes initial() not respecting insincere var-typing

Vars that are typed can actually store ANYTHING. The type is a weak promise that BYOND uses as a guarantee in some contexts (as in statics and constants) but not in others (as in normal variable accesses).

It's still pretty sour to me that we're supporting this, but that is indeed the BYOND behaviour.

Author: Altoids1

Content.Tests/DMProject/Tests/Const/Folding/InitialFolding.dm

@@ -3,7 +3,7 @@
 
 /datum/a
 	var/const/explicitly_const = 10
-	var/not_as_const = "apples"
+	var/static/not_as_const = "apples"
 
 /datum/a/field_test()
 	var/const/x = initial(not_as_const)

DMCompiler/DM/DMVariable.cs

@@ -13,13 +13,6 @@ class DMVariable {
         public DMExpression Value;
         public DMValueType ValType;
 
-        /// <summary>
-        /// This is something necessary for <see cref="Expressions.Initial.TryAsConstant(out Expressions.Constant)"/> to work correctly. <br/>
-        /// If a variable has a constant value, and is overridden with a new value, an initial() call is ambiguous, as it may refer to the old value or the new one, <br/>
-        /// depending on whether the src caller is of the child type or the parent type.
-        /// </summary>
-        bool _wasOverriddenWithNewConstant = false;
-
         public DMVariable(DreamPath? type, string name, bool isGlobal, bool isConst, DMValueType valType = DMValueType.Anything) {
             Type = type;
             Name = name;
@@ -42,14 +35,19 @@ public DMVariable WriteToValue(Expressions.Constant value)
                 Value = value;
                 return this;
             }
-            _wasOverriddenWithNewConstant = true;
             DMVariable clone = new DMVariable(Type,Name,IsGlobal,IsConst,ValType);
             clone.Value = value;
             return clone;
         }
 
+        /// <remarks>
+        /// Most variables are not safe to take as a constant-value, even in initial(), <br/>
+        /// because we may be arriving here from a member access that doesn't actually access this DMVariable. <br/>
+        /// Instead, it may be accessing (through duck-typing) a member someplace here.
+        /// Check the wording of the ref and read it very carefully: https://www.byond.com/docs/ref/#/operator/%2e
+        /// </remarks>
         public bool SafeToTakeAsConstant() {
-            return Value != null && (IsConst || !_wasOverriddenWithNewConstant);
+            return Value != null && (IsConst || IsGlobal); // with statics and consts, the type is "dominant" over the value can can just be taken as constant sometimes.
         }
 
         public bool TryAsJsonRepresentation(out object valueJson) {

DMCompiler/DM/Expressions/Builtins.cs

@@ -494,6 +494,9 @@ public override bool TryAsConstant(out Constant constant) {
                 case Dereference memberAccess: {
                     var obj = DMObjectTree.GetDMObject(memberAccess._expr.Path.GetValueOrDefault());
                     var variable = obj.GetVariable(memberAccess.PropertyName);
+                    if(variable == null) {
+                        variable = obj.GetGlobalVariable(memberAccess.PropertyName);
+                    }
                     if (variable != null && variable.SafeToTakeAsConstant()) {
                         return variable.Value.TryAsConstantWithLocation(out constant, Location);
                     }