Added visibility checks to forward declarations

src/frontend/compiler/targets/bytecode/target.nim

@@ -538,6 +538,8 @@ proc patchForwardDeclarations(self: BytecodeCompiler) =
     var pos: array[8, uint8]
     for (forwarded, position) in self.forwarded:
         impl = self.match(forwarded.ident.token.lexeme, forwarded.valueType, allowFwd=false)
+        if forwarded.isPrivate != impl.isPrivate:
+            self.error(&"implementation of '{impl.ident.token.lexeme}' has a mismatching visibility modifier from its forward declaration", impl.ident)
         if position == 0:
             continue
         pos = impl.codePos.toLong()

tests/fwd.pn

@@ -10,3 +10,5 @@ print(foo() == 42);
 
 fn foo: int {return 42;}  # Commenting this line will cause an error
 
+# Note: The forward declaration and its corresponding implementation
+# must have the same visibility!