feat!: Indexes for nodes in the AST (#414)

Indexes allow associating extra data with nodes in the AST
using an array and then quickly looking up the array to fetch
the extra data.

- Index eidx for expressions
- Index sidx for statements
- Index qidx for queries.

AST nodes are not cloneable. Therefore once a module is created,
it is not possible to accidentally create two nodes with the same
index inadvertently via clone.

Also added IndexChecker in debug builds. When a module is parsed,
it will assert that indexes have been constructed correctly.

AST Cleanup
- Make literal expressions (null, val, number, string etc) also structs
  to match all other expressions
- Merge True and False nodes into a single Bool node.

Also update dependencies.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

tests/parser/cases/package/package.yaml

@@ -4,20 +4,31 @@
 cases:
   - note: single-char
     rego: package a
+    num_expressions: 1
+    num_statements: 0
+    num_queries: 0
     package:
       span: package a
       refr:
         var: a
+        eidx: 0
 
   - note: simple
     rego: package test
+    num_expressions: 1
+    num_statements: 0
+    num_queries: 0
     package:
       span: package test
       refr:
         var: test
+        eidx: 0
 
   - note: dot
     rego: package a.b
+    num_expressions: 2
+    num_statements: 0
+    num_queries: 0
     package:
       span: package a.b
       refr:
@@ -25,10 +36,15 @@ cases:
           span: a.b
           refr:
             var: a
+            eidx: 0
           field: b
+        eidx: 1
 
   - note: multi-dot
     rego: package a.b.c
+    num_expressions: 3
+    num_statements: 0
+    num_queries: 0
     package:
       span: package a.b.c
       refr:
@@ -39,11 +55,17 @@ cases:
               span: a.b
               refr:
                 var: a
+                eidx: 0
               field: b
+            eidx: 1
           field: c
+        eidx: 2
 
   - note: bracket
     rego: package a["b"]
+    num_expressions: 3
+    num_statements: 0
+    num_queries: 0
     package:
       span: package a["b"]
       refr:
@@ -51,11 +73,17 @@ cases:
           span: a["b"]
           refr:
             var: a
+            eidx: 0
           index:
             string: b
+            eidx: 1
+        eidx: 2
 
   - note: multi-bracket
     rego: package a["b"]["c.d"]
+    num_expressions: 5
+    num_statements: 0
+    num_queries: 0
     package:
       span: package a["b"]["c.d"]
       refr:
@@ -66,35 +94,50 @@ cases:
               span: a["b"]
               refr:
                 var: a
+                eidx: 0
               index:
                 string: b
+                eidx: 1
+            eidx: 2
           index:
             string: c.d
+            eidx: 3
+        eidx: 4
 
   - note: complex
     rego: package a["b.c"].d["e.f"].g
+    num_expressions: 7
+    num_statements: 0
+    num_queries: 0
     package:
       span: package a["b.c"].d["e.f"].g
       refr:
         refdot:
           span: a["b.c"].d["e.f"].g
           refr:
-             refbrack:
-               span: a["b.c"].d["e.f"]
-               refr:
-                 refdot:
-                   span: a["b.c"].d
-                   refr:
-                     refbrack:
-                       span: a["b.c"]
-                       refr:
-                         var: a
-                       index:
-                         string: "b.c"
-                   field: d
-               index:
-                 string: e.f
+            refbrack:
+              span: a["b.c"].d["e.f"]
+              refr:
+                refdot:
+                  span: a["b.c"].d
+                  refr:
+                    refbrack:
+                      span: a["b.c"]
+                      refr:
+                        var: a
+                        eidx: 0
+                      index:
+                        string: "b.c"
+                        eidx: 1
+                    eidx: 2
+                  field: d
+                eidx: 3
+              index:
+                string: e.f
+                eidx: 4
+            eidx: 5
           field: g
+        eidx: 6
 
   - note: missing-package-keyword
     rego: packge a