Merge pull request #977 from stan-dev/bugfix/975-conditional-expr

Call eval on conditional return values

Author: WardBrian

src/stan_math_backend/Expression_gen.ml

@@ -568,8 +568,13 @@ and pp_expr ppf Expr.Fixed.({pattern; meta} as e) =
           pp_expr e
       in
       let tform ppf = pf ppf "(@[<hov 2>@,%a@ ?@ %a@ :@ %a@])" in
-      if types_match et ef then tform ppf pp_expr ec pp_expr et pp_expr ef
-      else tform ppf pp_expr ec promoted (e, et) promoted (e, ef)
+      let eval_pp ppf a =
+        if UnsizedType.is_eigen_type meta.type_ then
+          pf ppf "stan::math::eval(%a)" pp_expr a
+        else pf ppf "%a" pp_expr a
+      in
+      if types_match et ef then tform ppf pp_expr ec eval_pp et eval_pp ef
+      else tform ppf eval_pp ec promoted (e, et) promoted (e, ef)
   | Indexed (e, []) -> pp_expr ppf e
   | Indexed (e, idx) -> (
     match e.pattern with

test/integration/good/code-gen/conditional_expression_types.stan

@@ -0,0 +1,7 @@
+parameters {
+  vector[2] a;
+  vector[2] b;
+}
+transformed parameters {
+  vector[2] c = sum(a) > 1 ? 2*a+b : 2*a;
+}