Function optimizeStmtList

js/stmtlist.go:170–379

(list []js.IStmt, blockType blockType)

}

func optimizeStmtList(list []js.IStmt, blockType blockType) []js.IStmt {
	// merge expression statements as well as if/else statements followed by flow control statements
	if len(list) == 0 {
		return list
	}
	j := 0                           // write index
	for i := 0; i < len(list); i++ { // read index
		if ifStmt, ok := list[i].(*js.IfStmt); ok && !isEmptyStmt(ifStmt.Else) {
			// if(a)return b;else c  =>  if(a)b; c
			if unary, ok := ifStmt.Cond.(*js.UnaryExpr); ok && unary.Op == js.NotToken && isFlowStmt(lastStmt(ifStmt.Else)) {
				ifStmt.Cond = unary.X
				ifStmt.Body, ifStmt.Else = ifStmt.Else, ifStmt.Body
			}
			if isFlowStmt(lastStmt(ifStmt.Body)) {
				// if body ends in flow statement (return, throw, break, continue), we can remove the else statement and put its body in the current scope
				if blockStmt, ok := ifStmt.Else.(*js.BlockStmt); ok {
					blockStmt.Scope.Unscope()
					list = append(list[:i+1], append(blockStmt.List, list[i+1:]...)...)
				} else {
					list = append(list[:i+1], append([]js.IStmt{ifStmt.Else}, list[i+1:]...)...)
				}
				ifStmt.Else = nil
			}
		}

		list[i] = optimizeStmt(list[i])

		if _, ok := list[i].(*js.EmptyStmt); ok {
			k := i + 1
			for ; k < len(list); k++ {
				if _, ok := list[k].(*js.EmptyStmt); !ok {
					break
				}
			}
			list = append(list[:i], list[k:]...)
			i--
			continue
		}

		if 0 < i {
			// merge expression statements with expression, return, and throw statements
			if left, ok := list[i-1].(*js.ExprStmt); ok {
				if right, ok := list[i].(*js.ExprStmt); ok {
					right.Value = commaExpr(left.Value, right.Value)
					j--
				} else if returnStmt, ok := list[i].(*js.ReturnStmt); ok && returnStmt.Value != nil {
					returnStmt.Value = commaExpr(left.Value, returnStmt.Value)
					j--
				} else if throwStmt, ok := list[i].(*js.ThrowStmt); ok {
					throwStmt.Value = commaExpr(left.Value, throwStmt.Value)
					j--
				} else if forStmt, ok := list[i].(*js.ForStmt); ok {
					// TODO: only merge lhs expression that don't have 'in' or 'of' keywords (slow to check?)
					if forStmt.Init == nil {
						forStmt.Init = left.Value
						j--
					} else if decl, ok := forStmt.Init.(*js.VarDecl); ok && len(decl.List) == 0 {
						forStmt.Init = left.Value