Fix problem when using variable struct types in comprehensions

Fixes #901 on GitHub

Author: Dekker1

changes.rst

@@ -22,6 +22,8 @@ Bug fixes:
    with e.g. the ``--disable-warnings`` flag (:bugref:`893`).
 -  Fix incorrect generation of par versions of functions referencing top-level
    tuples/records containing var fields (:bugref:`919`).
+-  Fix problem where using an iterator of variable tuple or record types could
+   result in a segfault (:bugref:`901`).
 
 .. _v2.9.2:
 

lib/typecheck.cpp

@@ -2399,6 +2399,10 @@ class Typer {
           KeepAlive c_in = c->in(i) != nullptr
                                ? add_coercion(_env, _model, c->in(i), c, Expression::type(c->in(i)))
                                : nullptr;
+          auto* decl_ti = c->decl(i, j)->ti();
+          if (decl_ti->type().structBT() && decl_ti->domain() == nullptr) {
+            decl_ti->setStructDomain(_env, decl_ti->type());
+          }
           if (!whereMap[c->decl(i, j)].empty()) {
             // need a generator for all the decls up to this point
             Expression* whereExpr = whereMap[c->decl(i, j)][0];

tests/spec/unit/regression/github_901.mzn

@@ -0,0 +1,11 @@
+/***
+!Test
+solvers: [gecode]
+expected: !Result
+- !Solution
+  i: [0,0]
+  j: [[0,0]]
+***/
+
+array[1..2] of var 0..0: i;
+array[_] of var tuple(int, int): j ::output = [k | k in [if sum(i) > 1 then (0, 0) else (0, 0) endif]];