internal/core/runtime: assign first label to _.

Change-Id: I55a3291e8aecf93bb9465f2cccc52ed7121520a9 Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7841 Reviewed-by: CUE cueckoo <cueckoo@gmail.com> Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
cue-lang · Dec 2, 2020 · 63594ef · 63594ef
1 parent e77ccb1
commit 63594ef
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Showing 9 changed files with 36 additions and 21 deletions.
diff --git a/cue/testdata/export/004.txtar b/cue/testdata/export/004.txtar
@@ -17,15 +17,15 @@ _bar:   int
 {
   {
     $type: 3
-    "_": int
+    _: int
     "_foo": int
     _bar: int
   }
 }
 -- out/eval --
 (struct){
   $type: (int){ 3 }
-  "_": (int){ int }
+  _: (int){ int }
   "_foo": (int){ int }
   _bar: (int){ int }
 }
diff --git a/cue/testdata/references/index.txtar b/cue/testdata/references/index.txtar
@@ -37,7 +37,7 @@ indexDoesNotDistribute: index out of range [0] with length 0:
     ./in.cue:10:41
 doesNotDistributeType.a: invalid list index "3" (type string):
     ./in.cue:13:24
-stringIndexToList: invalid list index _ (type string):
+stringIndexToList: invalid list index "" (type string):
     ./in.cue:16:24
 indexOutOfBounds2: invalid operand 2 (found int, want list or struct):
     ./in.cue:17:20
@@ -77,7 +77,7 @@ Result:
     }
   }
   stringIndexToList: (_|_){
-    // [eval] stringIndexToList: invalid list index _ (type string):
+    // [eval] stringIndexToList: invalid list index "" (type string):
     //     ./in.cue:16:24
   }
   indexOutOfBounds2: (_|_){

diff --git a/cue/testdata/references/labels.txtar b/cue/testdata/references/labels.txtar
@@ -45,6 +45,11 @@ c1: C="foo\(bar)": [D=string]: {
 }
 c1: foo3: x: _
 
+emptyLabel: {
+    "": 1
+    a: emptyLabel[""]
+}
+
 // TODO: support. Also not yet supported in old implementation.
 // c10: {
 // 	C=[string]: {
@@ -95,6 +100,10 @@ c1: foo3: x: _
       }
     }
   }
+  emptyLabel: (struct){
+    "": (int){ 1 }
+    a: (int){ 1 }
+  }
 }
 -- out/compile --
 --- in.cue
@@ -175,4 +184,8 @@ c1: foo3: x: _
       x: _
     }
   }
+  emptyLabel: {
+    "": 1
+    a: 〈1;emptyLabel〉[""]
+  }
 }
diff --git a/cue/testdata/resolve/016_index.txtar b/cue/testdata/resolve/016_index.txtar
@@ -97,7 +97,7 @@ c: invalid list index "3" (type string):
     ./in.cue:3:20
 d: index out of range [0] with length 0:
     ./in.cue:4:16
-e1: invalid list index _ (type string):
+e1: invalid list index "" (type string):
     ./in.cue:6:9
 e2: invalid operand 2 (found int, want list or struct):
     ./in.cue:7:5
@@ -132,7 +132,7 @@ Result:
   l: (#list){
   }
   e1: (_|_){
-    // [eval] e1: invalid list index _ (type string):
+    // [eval] e1: invalid list index "" (type string):
     //     ./in.cue:6:9
   }
   e2: (_|_){

diff --git a/internal/core/debug/compact.go b/internal/core/debug/compact.go
@@ -193,7 +193,7 @@ func (w *compactPrinter) node(n adt.Node) {
 		w.label(x.ImportPath)
 
 	case *adt.LetReference:
-		w.label(x.Label)
+		w.ident(x.Label)
 
 	case *adt.SelectorExpr:
 		w.node(x.X)
@@ -300,9 +300,9 @@ func (w *compactPrinter) node(n adt.Node) {
 
 	case *adt.ForClause:
 		w.string("for ")
-		w.label(x.Key)
+		w.ident(x.Key)
 		w.string(", ")
-		w.label(x.Value)
+		w.ident(x.Value)
 		w.string(" in ")
 		w.node(x.Src)
 		w.string(" ")
@@ -316,7 +316,7 @@ func (w *compactPrinter) node(n adt.Node) {
 
 	case *adt.LetClause:
 		w.string("let ")
-		w.label(x.Label)
+		w.ident(x.Label)
 		w.string(" = ")
 		w.node(x.Expr)
 		w.string(" ")

diff --git a/internal/core/debug/debug.go b/internal/core/debug/debug.go
@@ -84,6 +84,10 @@ func (w *printer) label(f adt.Feature) {
 	w.string(w.labelString(f))
 }
 
+func (w *printer) ident(f adt.Feature) {
+	w.string(f.IdentString(w.index))
+}
+
 // TODO: fold into label once :: is no longer supported.
 func (w *printer) labelString(f adt.Feature) string {
 	if f.IsHidden() {
@@ -378,7 +382,7 @@ func (w *printer) node(n adt.Node) {
 		w.string(openTuple)
 		w.string(strconv.Itoa(int(x.UpCount)))
 		w.string(";let ")
-		w.label(x.Label)
+		w.ident(x.Label)
 		w.string(closeTuple)
 
 	case *adt.SelectorExpr:
@@ -490,9 +494,9 @@ func (w *printer) node(n adt.Node) {
 
 	case *adt.ForClause:
 		w.string("for ")
-		w.label(x.Key)
+		w.ident(x.Key)
 		w.string(", ")
-		w.label(x.Value)
+		w.ident(x.Value)
 		w.string(" in ")
 		w.node(x.Src)
 		w.string(" ")
@@ -506,7 +510,7 @@ func (w *printer) node(n adt.Node) {
 
 	case *adt.LetClause:
 		w.string("let ")
-		w.label(x.Label)
+		w.ident(x.Label)
 		w.string(" = ")
 		w.node(x.Expr)
 		w.string(" ")

diff --git a/internal/core/export/label.go b/internal/core/export/label.go
@@ -24,9 +24,6 @@ import (
 )
 
 func (e *exporter) stringLabel(f adt.Feature) ast.Label {
-	if f == 0 {
-		return ast.NewIdent("_")
-	}
 	x := f.Index()
 	switch f.Typ() {
 	case adt.IntLabel:
@@ -38,7 +35,7 @@ func (e *exporter) stringLabel(f adt.Feature) ast.Label {
 
 	case adt.StringLabel:
 		s := e.ctx.IndexToString(int64(x))
-		if !ast.IsValidIdent(s) {
+		if f == 0 || !ast.IsValidIdent(s) {
 			return ast.NewLit(token.STRING, literal.Label.Quote(s))
 		}
 		fallthrough

diff --git a/internal/core/runtime/index.go b/internal/core/runtime/index.go
@@ -62,7 +62,8 @@ var (
 )
 
 func init() {
-	getKey("")
+	// Ensure label 0 is assigned to _.
+	getKey("_")
 }
 
 func getKey(s string) int64 {

diff --git a/internal/filetypes/types.go b/internal/filetypes/types.go