Eliminate the unnecessary ast.StdAst

The initially empty ast.StdAst was created to break the circular
dependency. The generation of stdlib AST used to depend on
the primary "jsonnet" package, which meant that "jsonnet"
could not depend on it directly. Hence stdlib needed to be put
in the ast package. Now dumpstdlibast no longer depends on Jsonnet,
so we can get rid of this complication.

All code using ast.StdAst should now use astgen.StdAst.

ast/stdast.go

@@ -1,8 +0,0 @@
-package ast
-
-// StdAst is the AST for the standard library.
-//
-// Its inital value is the Jsonnet null value, such that the standard library is not available
-// during evaluation. Set this variable to point at a non-null AST node to make that tree available
-// as the standard library.
-var StdAst Node = &LiteralNull{}

astgen/stdast.go

@@ -11,9 +11,6 @@ import (
 	"github.com/google/go-jsonnet/ast"
 )
 
-func init() {
-	ast.StdAst = StdAst
-}
 var p3Var = "$"
 var p3 = &p3Var
 var p8Var = "object <anonymous>"

c-bindings/c-bindings.go

@@ -6,8 +6,6 @@ import (
 	"os"
 
 	"github.com/google/go-jsonnet"
-	"github.com/google/go-jsonnet/ast"
-	"github.com/google/go-jsonnet/astgen"
 
 	// #cgo CXXFLAGS: -std=c++11 -Wall -I../cpp-jsonnet/include
 	// #include "internal.h"
@@ -159,5 +157,4 @@ func jsonnet_tla_code(vmRef *C.struct_JsonnetVm, key, value *C.char) {
 }
 
 func main() {
-	ast.StdAst = astgen.StdAst
 }

cmd/dumpstdlibast/dumpstdlibast.go

@@ -62,7 +62,4 @@ import (
 	"github.com/google/go-jsonnet/ast"
 )
 
-func init() {
-	ast.StdAst = StdAst
-}
 `[1:]

cmd/jsonnet/cmd.go

@@ -32,8 +32,6 @@ import (
 	"github.com/fatih/color"
 
 	"github.com/google/go-jsonnet"
-	"github.com/google/go-jsonnet/ast"
-	"github.com/google/go-jsonnet/astgen"
 )
 
 func nextArg(i *int, args []string) string {
@@ -473,7 +471,6 @@ func writeOutputFile(output string, outputFile string, createDirs bool) error {
 }
 
 func main() {
-	ast.StdAst = astgen.StdAst
 	// https://blog.golang.org/profiling-go-programs
 	var cpuprofile = os.Getenv("JSONNET_CPU_PROFILE")
 	if cpuprofile != "" {

interpreter.go

@@ -24,6 +24,7 @@ import (
 	"sort"
 
 	"github.com/google/go-jsonnet/ast"
+	"github.com/google/go-jsonnet/astgen"
 )
 
 // TODO(sbarzowski) use it as a pointer in most places b/c it can sometimes be shared
@@ -1119,7 +1120,7 @@ func evaluateStd(i *interpreter) (value, error) {
 	)
 	evalLoc := ast.MakeLocationRangeMessage("During evaluation of std")
 	evalTrace := TraceElement{loc: &evalLoc}
-	node := ast.StdAst
+	node := astgen.StdAst
 	return i.EvalInCleanEnv(evalTrace, &beforeStdEnv, node, false)
 }
 

jsonnet_test.go

@@ -4,15 +4,8 @@ import (
 	"bytes"
 	"testing"
 	"unicode/utf8"
-
-	"github.com/google/go-jsonnet/ast"
-	"github.com/google/go-jsonnet/astgen"
 )
 
-func init() {
-	ast.StdAst = astgen.StdAst
-}
-
 type errorFormattingTest struct {
 	name      string
 	input     string