Bugfix (and typo fix) in results testing for parametric mode.

If the result is a single parameter (p in the included test case),
findAllConstants returns a new Expression, not a modified one.

prism-tests/functionality/verify/param/param-simple.prism

@@ -0,0 +1,16 @@
+// Trivial test of parametric model checking
+// (also tests a bugfix in the results testing when the result is just a lone parameter)
+
+dtmc
+
+const double p;
+
+module M
+
+	// local state
+	s : [0..7] init 0;
+	
+	[] s=0 -> p : (s'=1) + 1-p : (s'=2);
+	[] s>0 -> true;
+	
+endmodule

prism-tests/functionality/verify/param/param-simple.prism.props

@@ -0,0 +1,5 @@
+// RESULT: p
+P=? [ F s=1 ];
+
+// RESULT: 1-p
+P=? [ F s=2 ];

prism-tests/functionality/verify/param/param-simple.prism.props.args

@@ -0,0 +1 @@
+-param p

prism/src/param/ParamResult.java

@@ -148,7 +148,7 @@ public class ParamResult
 				for (String p : modelBuilder.getParameterNames()) {
 					constantList.addConstant(new ExpressionIdent(p), null, TypeDouble.getInstance());
 				}
-				exprExpected.findAllConstants(constantList);
+				exprExpected = (Expression) exprExpected.findAllConstants(constantList);
 				exprExpected.typeCheck();
 
 				// replace constants in the expression that have a value