Extend shl4 test

The operands of relational expressions are given an evaluation context with
the max width of both operands.

Hence, an expression can be equal to two different values.

Author: kroening

regression/verilog/expressions/shl4.sv

@@ -1,6 +1,12 @@
 module main;
 
+  // The arguments of === are adjusted to the maximum of the
+  // self-determined widths of the lhs and rhs.
+  // Hence, 4'b1111 << 1 is equal both to 4'b1110 and 5'b11110.
+  assert final (4'b1111 << 1 === 4'b1110);
   assert final (4'b1111 << 1 === 5'b11110);
-  assert final (1 << 6 === 64);
+
+  assert final (1'b1 << 6 === 64);
+  assert final (1'b1 << 6 === 1'b0);
 
 endmodule