added lox test files

lox.t/assignment/associativity.lox

@@ -0,0 +1,9 @@
+var a = "a";
+var b = "b";
+var c = "c";
+
+// Assignment is right-associative.
+a = b = c;
+print a; // expect: c
+print b; // expect: c
+print c; // expect: c

lox.t/assignment/global.lox

@@ -0,0 +1,8 @@
+var a = "before";
+print a; // expect: before
+
+a = "after";
+print a; // expect: after
+
+print a = "arg"; // expect: arg
+print a; // expect: arg

lox.t/assignment/grouping.lox

@@ -0,0 +1,2 @@
+var a = "a";
+(a) = "value"; // Error at '=': Invalid assignment target.

lox.t/assignment/infix_operator.lox

@@ -0,0 +1,3 @@
+var a = "a";
+var b = "b";
+a + b = "value"; // Error at '=': Invalid assignment target.

lox.t/assignment/local.lox

@@ -0,0 +1,10 @@
+{
+  var a = "before";
+  print a; // expect: before
+
+  a = "after";
+  print a; // expect: after
+
+  print a = "arg"; // expect: arg
+  print a; // expect: arg
+}

lox.t/assignment/prefix_operator.lox

@@ -0,0 +1,2 @@
+var a = "a";
+!a = "value"; // Error at '=': Invalid assignment target.

lox.t/assignment/syntax.lox

@@ -0,0 +1,5 @@
+// Assignment on RHS of variable.
+var a = "before";
+var c = a = "var";
+print a; // expect: var
+print c; // expect: var

lox.t/assignment/to_this.lox

@@ -0,0 +1,7 @@
+class Foo {
+  Foo() {
+    this = "value"; // Error at '=': Invalid assignment target.
+  }
+}
+
+Foo();

lox.t/assignment/undefined.lox

@@ -0,0 +1 @@
+unknown = "what"; // expect runtime error: Undefined variable 'unknown'.