1 files changed, 6 insertions, 1 deletions
diff --git a/src/parse.cff b/src/parse.cff
index a065739..5c3ac63 100644
--- a/src/parse.cff
+++ b/src/parse.cff
@@ -3060,6 +3060,8 @@ fn parsedecls(P *Parser, loc Loc, yield DeclYielder, yarg *void, toplevel bool)
 
    case lexmatch(P, &tok, :kw_def);
       do {
+         let konst = lexmatch(P, #null, :kw_const);
+
          let tok = lexexpect(P, :ident),
              name = tok.u.ident,
              ini Expr #?,
@@ -3076,7 +3078,10 @@ fn parsedecls(P *Parser, loc Loc, yield DeclYielder, yarg *void, toplevel bool)
          if !typematchestarg(ty, ini.ty) {
             err(P, ini.loc, "incompatible initializer (%t, expected %t)", ini.ty, ty);
          }
-         fold(&ini);
+         let f = fold(&ini);
+         if konst and !f {
+            err(P, ini.loc, "cannot evaluate expression at compile time");
+         }
          decl = putdecl(P, tok.loc, { name, tok.loc, .u: :Def(ini) });
          if yield {
             yield(decl, yarg);