GetTypeName in CST

go/src/miller/dsl/cst/assignments.go

@@ -58,6 +58,7 @@ func NewAssignmentNode(
 func (this *AssignmentNode) Execute(state *State) {
 	rvalue := this.rvalue.Evaluate(state)
 	if !rvalue.IsAbsent() {
+		// xxx need to propagate the error coming back in the Execute() API
 		this.lvalue.Assign(&rvalue, state)
 	}
 }

go/src/miller/dsl/cst/lvalues.go

@@ -98,9 +98,10 @@ func (this *IndirectFieldNameLvalueNode) Assign(
 	lhsFieldName := this.lhsFieldNameExpression.Evaluate(state)
 
 	if !lhsFieldName.IsString() {
-		// xxx make and use a Mlrval GetTypeName()
 		return errors.New(
-			"Miller DSL: computed field name [%s] should be a string but is not.",
+			"Miller DSL: computed field name [%s] should be a string but was " +
+				lhsFieldName.GetTypeName() +
+				".",
 		)
 	}
 

go/src/miller/lib/mlrval.go

@@ -93,3 +93,15 @@ const (
 	// function pointers which is MT_DIM x MT_DIM.
 	MT_DIM = 9
 )
+
+var TYPE_NAMES = [MT_DIM]string{
+	"error",
+	"absent",
+	"void",
+	"string",
+	"int",
+	"float",
+	"bool",
+	"array",
+	"map",
+}

go/src/miller/lib/mlrval_accessors.go

@@ -4,6 +4,10 @@ func (this *Mlrval) GetType() MVType {
 	return this.mvtype
 }
 
+func (this *Mlrval) GetTypeName() string {
+	return TYPE_NAMES[this.mvtype]
+}
+
 func (this *Mlrval) IsError() bool {
 	return this.mvtype == MT_ERROR
 }

go/todo.txt

@@ -2,9 +2,7 @@
 TOP OF LIST:
 
 * monday:
-  o lib.GetTypeName
   o rename MlrvalOrFunction in the DSL
-  ! tags file
   ? ENV
 
 * array/map
@@ -60,8 +58,13 @@ TOP OF LIST:
   o begin/end blocks
   o oosvars
   o indirect field names, at LHS and RHS
+  o full indexable at LHS/RHS -- e.g. $*["a"] = $b
   o support the filter verb
 
+! the DSL needs a full, written-down-and-published spell-out of reference/copy semantics
+* then careful CST impl
+! likewise error-eval semantics
+
 ----------------------------------------------------------------
 MAYBE: