Fixes the early evaluation problem with assert statements in P (#695)

Author: ankushdesai

Src/PCompiler/CompilerCore/Backend/IRTransformer.cs

@@ -352,11 +352,12 @@ private List<IPStmt> SimplifyStatement(IPStmt statement)
                 case AssertStmt assertStmt:
                     (var assertExpr, var assertDeps) = SimplifyExpression(assertStmt.Assertion);
                     (var messageExpr, var messageDeps) = SimplifyExpression(assertStmt.Message);
-
-                    return assertDeps.Concat(messageDeps).Concat(new[]
+                    var ifStmtForAssert = new IfStmt(location, assertExpr, new NoStmt(location), new CompoundStmt(
+                        location, messageDeps.Concat(new[]
                         {
                             new AssertStmt(location, assertExpr, messageExpr)
-                        })
+                        }).ToList()));
+                    return assertDeps.Concat(new List<IPStmt>{ifStmtForAssert})
                         .ToList();
 
                 case AssignStmt assignStmt:

Tst/RegressionTests/Feature3Exprs/Correct/assertMessage/assertMessage.p

@@ -0,0 +1,8 @@
+machine Main {
+  start state Init {
+    entry {
+      var m: map[int, int];
+      assert !(1 in m), format("Yay! {0}", m[1]);
+    }
+  }
+}