Multiple assignment error is not reported

[horkhe]

func Foo() (int, int) {
    a, b := 0, 0
    a, b = 1, 1
    a, b += 1, 1 // Should be error: `syntax error: unexpected op=, expecting := or = or comma`
    return a, b
}

[dlsniper]

This would be a good test for #1668. I should also update that PR. Thank you for reporting this.

[dlsniper]

I've fixed this in #1688, thanks for reporting.

[sjamesr]

@dlsniper Did you mean #1668?

I think there is a problem in the go.bnf grammar:

left AssignmentStatement ::= assign_op ExpressionList {pin=1}
assign_op ::= '=' | '+=' | '-=' | '|=' | '^=' | '*=' | '/=' | '%=' | '<<=' | '>>=' | '&=' | '&^='

According to the go grammar, only := and = may appear between expression lists. The other operators may only appear between expression productions.

It seems to me that this should not be an inspection but should actually be reported as an error, the code in the example is not Go. :)

[ignatov]

Also we should improve the spec about assignments:

Assignment = ExpressionList assign_op ExpressionList .
assign_op = [ add_op | mul_op ] "=" .