size pragma only allowed for objects and enums

compiler/semstmts.nim

@@ -1787,6 +1787,17 @@ proc typeSectionFinalPass(c: PContext, n: PNode) =
     # check the style here after the pragmas have been processed:
     styleCheckDef(c, s)
     # compute the type's size and check for illegal recursions:
+    if a[0].kind == nkPragmaExpr:
+      let pragmas = a[0][1]
+      for i in 0 ..< pragmas.len:
+        if pragmas[i].kind == nkExprColonExpr and
+            pragmas[i][0].kind == nkIdent and
+            whichKeyword(pragmas[i][0].ident) == wSize:
+          if s.typ.kind notin {tyObject, tyEnum}:
+            # EventType* {.size: sizeof(uint32).} = enum
+            # AtomicFlag* {.importc: "atomic_flag", header: "<stdatomic.h>", size: 1.} = object
+            localError(c.config, pragmas[i].info, "size pragma only allowed for objects and enums")
+
     if a[1].kind == nkEmpty:
       var x = a[2]
       if x.kind in nkCallKinds and nfSem in x.flags: