Disallow coercion of sets into multidimensional arrays

Fixes #656

changes.rst

@@ -70,6 +70,7 @@ Bug fixes:
 -  Fix handling of domains for tuple and record types.
 -  Fix index set checking for tuples and records which contain arrays.
 -  Fix the handling of domain and index set expressions in aliases.
+-  Fix incorrect coercion of sets into multidimensional arrays (:bugref:`656`).
 
 .. _v2.7.0:
 

lib/typecheck.cpp

@@ -1447,13 +1447,18 @@ KeepAlive add_coercion(EnvI& env, Model* m, Expression* e, const Type& funarg_t)
   }
   GCLock lock;
   Call* c = nullptr;
-  if (e->type().dim() == 0 && funarg_t.dim() != 0) {
+  if (e->type().isSet() && funarg_t.dim() != 0) {
     if (e->type().isvar()) {
       throw TypeError(env, e->loc(), "cannot coerce var set into array");
     }
     if (e->type().isOpt()) {
       throw TypeError(env, e->loc(), "cannot coerce opt set into array");
     }
+    if (funarg_t.dim() > 1) {
+      std::stringstream ss;
+      ss << "cannot coerce set into " << funarg_t.dim() << "-dimensional array";
+      throw TypeError(env, e->loc(), ss.str());
+    }
     std::vector<Expression*> set2a_args(1);
     set2a_args[0] = e;
     Call* set2a = Call::a(e->loc(), ASTString("set2array"), set2a_args);

tests/spec/unit/regression/github_656.mzn

@@ -0,0 +1,10 @@
+/***
+!Test
+solvers:
+- gecode
+expected: !Error
+  regex: .*cannot coerce set into 2-dimensional array.*
+***/
+
+% Previously sets were incorrectly allowed to coerce to multidimensional arrays.
+output [show2d(1..2)];