Method evaluateConstValue

package.go:78–187

(file *ast.File, iota int, expr ast.Expr, globalEvaluator ConstVariableGlobalEvaluator, recursiveStack map[string]struct{})

}

func (pkg *PackageDefinitions) evaluateConstValue(file *ast.File, iota int, expr ast.Expr, globalEvaluator ConstVariableGlobalEvaluator, recursiveStack map[string]struct{}) (interface{}, ast.Expr) {
	switch valueExpr := expr.(type) {
	case *ast.Ident:
		if valueExpr.Name == "iota" {
			return iota, nil
		}
		if pkg.ConstTable != nil {
			if cv, ok := pkg.ConstTable[valueExpr.Name]; ok {
				return globalEvaluator.EvaluateConstValue(pkg, cv, recursiveStack)
			}
		}
	case *ast.SelectorExpr:
		pkgIdent, ok := valueExpr.X.(*ast.Ident)
		if !ok {
			return nil, nil
		}
		return globalEvaluator.EvaluateConstValueByName(file, pkgIdent.Name, valueExpr.Sel.Name, recursiveStack)
	case *ast.BasicLit:
		switch valueExpr.Kind {
		case token.INT:
			// handle underscored number, such as 1_000_000
			if strings.ContainsRune(valueExpr.Value, '_') {
				valueExpr.Value = strings.Replace(valueExpr.Value, "_", "", -1)
			}
			if len(valueExpr.Value) >= 2 && valueExpr.Value[0] == '0' {
				var start, base = 2, 8
				switch valueExpr.Value[1] {
				case 'x', 'X':
					//hex
					base = 16
				case 'b', 'B':
					//binary
					base = 2
				default:
					//octet
					start = 1
				}
				if x, err := strconv.ParseInt(valueExpr.Value[start:], base, 64); err == nil {
					return int(x), nil
				} else if x, err := strconv.ParseUint(valueExpr.Value[start:], base, 64); err == nil {
					return x, nil
				} else {
					panic(err)
				}
			}

			//a basic literal integer is int type in default, or must have an explicit converting type in front
			if x, err := strconv.ParseInt(valueExpr.Value, 10, 64); err == nil {
				return int(x), nil
			} else if x, err := strconv.ParseUint(valueExpr.Value, 10, 64); err == nil {
				return x, nil
			} else {
				panic(err)
			}
		case token.STRING:
			if valueExpr.Value[0] == '`' {
				return valueExpr.Value[1 : len(valueExpr.Value)-1], nil
			}