新行上的右括号不能编译

Question

This code compiles fine:

return func(w http.ResponseWriter, r *http.Request) {


    if r.Header.Get("tc_req_body_type") != m["request_body"] {
        fmt.Println(
            strings.Join([]string{"types are different", " actual:",
                r.Header.Get("tc_req_body_type"), "expected:", m["request_body"]}," "))
    }

    if r.Header.Get("tc_resp_body_type") != m["response_body"] {
        fmt.Println(
            strings.Join([]string{"types are different", " actual: ",
                r.Header.Get("tc_req_body_type"), " expected: ", m["request_body"]}," "))
    }


    fmt.Printf("Req: %s
", r.URL.Path)

    h.ServeHTTP(w, r)
}

but if I add a new-line after the last paren in the fmt.Println call:

return func(w http.ResponseWriter, r *http.Request) {


    if r.Header.Get("tc_req_body_type") != m["request_body"] {
        fmt.Println(
            strings.Join([]string{"types are different", " actual:",
                r.Header.Get("tc_req_body_type"), "expected:", m["request_body"]}," ")
        )  // <<< here
    }

    if r.Header.Get("tc_resp_body_type") != m["response_body"] {
        fmt.Println(
            strings.Join([]string{"types are different", " actual: ",
                r.Header.Get("tc_req_body_type"), " expected: ", m["request_body"]}," ")
        )  // <<<  here
    }


    fmt.Printf("Req: %s
", r.URL.Path)

    h.ServeHTTP(w, r)
}

now it won't compile, what's the reason for this? I added a comment next to difference in the second code sample, also just writing more b/c it said my question had too much code and not enough words thanks.

Answer 1

The Go Programming Language Specification

Semicolons

The formal grammar uses semicolons ";" as terminators in a number of productions. Go programs may omit most of these semicolons using the following two rules:

1. When the input is broken into tokens, a semicolon is automatically inserted into the token stream immediately after a line's final token if that token is

   . an identifier

   . an integer, floating-point, imaginary, rune, or string literal

   . one of the keywords break, continue, fallthrough, or return

   . one of the operators and punctuation ++, --, ), ], or }

2. To allow complex statements to occupy a single line, a semicolon may be omitted before a closing ")" or "}".

---

syntax error: unexpected newline, expecting comma or )

Add the commas at the end of the argument list lines to avoid the automatic insertion of semicolons.

r.Header.Get("tc_req_body_type"), "expected:", m["request_body"]}, " "),
) 

r.Header.Get("tc_req_body_type"), " expected: ", m["request_body"]}, " "),
)