Disallow declarations of parents after functions.

Author: threeifbyair

regression-tests/pure2-bugfix-for-functions-before-superclasses.cpp2

@@ -0,0 +1,8 @@
+crash_m0b: type = {
+}
+
+crash_m0c: type = {
+  name: i32;
+  get_name: (this) -> i32 = { return name; }
+  this: crash_m0b;
+}

regression-tests/test-results/pure2-bugfix-for-functions-before-superclasses.cpp2.output

@@ -0,0 +1,3 @@
+pure2-bugfix-for-functions-before-superclasses.cpp2...
+pure2-bugfix-for-functions-before-superclasses.cpp2(7,3): error: a type cannot declare a parent after defining a function
+

source/sema.h

@@ -2037,6 +2037,7 @@ class sema
         if (n.is_type()) {
             auto compound_stmt = n.initializer->get_if<compound_statement_node>();
             assert (compound_stmt);
+            bool seen_function = false;
             for (auto& stmt : compound_stmt->statements) {
                 if (
                     !stmt->is_declaration()
@@ -2049,6 +2050,24 @@ class sema
                     );
                     return false;
                 }
+                auto stmt_decl = stmt->get_if<declaration_node>();
+                //  If this is a declaration, check if it's a function
+                if (stmt_decl && stmt_decl->is_function())
+                    seen_function = true;
+
+                //  If this is called 'this', then make sure we haven't seen any functions
+                if (
+                    stmt_decl
+                    && stmt_decl->has_name("this")
+                    && seen_function
+                    )
+                {
+                    handle_error(
+                        stmt->position(),
+                        "a type cannot declare a parent after defining a function"
+                    );
+                    return false;
+                }
             }
         }