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cmd/compile: invalid literal 0b.p produces 4 error messages #33961

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griesemer opened this issue Aug 30, 2019 · 5 comments
Closed

cmd/compile: invalid literal 0b.p produces 4 error messages #33961

griesemer opened this issue Aug 30, 2019 · 5 comments
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Go1.14

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@griesemer
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Compiling

package p
const _ = 0b.p

produces 4 error messages:

x.go:2:13: invalid radix point in binary literal
x.go:2:14: binary literal has no digits
x.go:2:14: 'p' exponent requires hexadecimal mantissa
x.go:2:15: exponent has no digits

The first one would suffice.
@griesemer griesemer self-assigned this Aug 30, 2019
@griesemer griesemer added this to the Go1.14 milestone Aug 30, 2019
@ianlancetaylor
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gccgo reports

foo.go:2:11: error: invalid numeric literal
    2 | const _ = 0b.p
      |           ^
foo.go:2:13: error: reference to field ‘p’ in object which has no fields or methods
    2 | const _ = 0b.p
      |             ^

@griesemer
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griesemer commented Aug 30, 2019 •
edited

@ianlancetaylor With Go 1.14, the number scanner takes the approach of a very much relaxed number syntax and so all of 0b.p is considered a (invalid) number. Not clear if that's better than what we had before - but it is certainly easy to lex. Anyway, this specific issue is trivial to fix and actually simplifies the code.

@gopherbot
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Change https://golang.org/cl/192499 mentions this issue: cmd/compile/internal/scanner: report at most one lexical error per token

@griesemer
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@ianlancetaylor What does gccgo report for "\?\777\xax" ?

@ianlancetaylor
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What does gccgo report for "?\777\xax" ?

foo.go:3:10: error: invalid character after ‘\’
    3 | var S = "\?\777\xax"
      |          ^
foo.go:3:12: error: invalid octal constant
    3 | var S = "\?\777\xax"
      |            ^
foo.go:3:16: error: invalid hex character
    3 | var S = "\?\777\xax"
      |                ^

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