Start getting block scope working.

test/if.wren

@@ -36,3 +36,11 @@ if
 // Newline after "else".
 if (false) io.write("bad") else
 io.write("good") // expect: good
+
+// Definition in then arm.
+if (true) var a = io.write("ok") // expect: ok
+if (true) class Foo {} // no error
+
+// Definition in else arm.
+if (false) null else var a = io.write("ok") // expect: ok
+if (true) null else class Foo {} // no error

test/scope_if.wren

@@ -0,0 +1,9 @@
+// Create a local scope for the 'then' expression.
+var a = "out"
+if (true) var a = "in"
+io.write(a) // expect: out
+
+// Create a local scope for the 'else' expression.
+var b = "out"
+if (false) "dummy" else var b = "in"
+io.write(b) // expect: out

test/scope_reuse_in_different_blocks.wren

@@ -0,0 +1,9 @@
+{
+  var a = "first"
+  io.write(a) // expect: first
+}
+
+{
+  var a = "second"
+  io.write(a) // expect: second
+}

test/scope_while.wren

@@ -0,0 +1,7 @@
+// Body has its own scope.
+var a = "outer"
+var i = 0
+while ((i = i + 1) <= 1) var a = "inner"
+io.write(a) // expect: outer
+
+// TODO(bob): What about condition?

test/while.wren

@@ -29,3 +29,7 @@ var f = while (e < 3) {
   e = e + 1
 }
 io.write(f) // expect: null
+
+// Definition body.
+while (false) var a = "ok" // no error
+while (false) class Foo {} // no error