ts/ast: Add regexp Ident validator

generator.go

@@ -444,10 +444,15 @@ func orEnum(v cue.Value) ([]ts.Expr, error) {
 			return nil, valError(v, "typescript enums may only be generated from a disjunction of concrete strings or numbers")
 		}
 
+		id := ts.Ident(strings.Title(text))
+		if id.Validate() != nil {
+			return nil, valError(v, "title casing of enum member %q produces an invalid typescript identifier; memberNames must be explicitly given in @cuetsy attribute", text)
+		}
+
 		fields = append(fields, tsast.AssignExpr{
 			// Simple mapping of all enum values (which we are assuming are in
 			// lowerCamelCase) to corresponding CamelCase
-			Name:  ts.Ident(strings.Title(text)),
+			Name:  id,
 			Value: tsprintConcrete(dv),
 		})
 	}

ts/ast/ast.go

@@ -1,7 +1,9 @@
 package ast
 
 import (
+	"errors"
 	"fmt"
+	"regexp"
 	"strings"
 )
 
@@ -96,6 +98,10 @@ type Ident struct {
 	As string
 }
 
+var identRegexp = regexp.MustCompile("^[a-zA-Z_$][0-9a-zA-Z_$]*$")
+
+var ErrBadIdent = errors.New("typescript idents must contain only alphanumeric characters")
+
 func (i Ident) ident() {}
 func (i Ident) expr()  {}
 func (i Ident) String() string {
@@ -107,6 +113,16 @@ func (i Ident) String() string {
 	return n
 }
 
+func (i Ident) Validate() error {
+	if !identRegexp.MatchString(i.Name) {
+		return ErrBadIdent
+	}
+	if i.As != "" && !identRegexp.MatchString(i.Name) {
+		return ErrBadIdent
+	}
+	return nil
+}
+
 func None() Expr {
 	return Ident{}
 }