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cmd/compile/internal/syntax: better scanner error messages 

This is one of several changes that were part of a larger rewrite
which I made in early 2019 after switching to the new number literal
syntax implementation. The purpose of the rewrite was to simplify
reading of source code (Unicode character by character) and speed up
the scanner but was never submitted for review due to other priorities.

Part 2 of 3:

This change contains improvements to the scanner error messages:

- Use "rune literal" rather than "character literal" to match the
  spec nomenclature.

- Shorter, more to the point error messages.
  (For instance, "more than one character in rune literal" rather
  than "invalid character literal (more than one character)", etc.)

Change-Id: I1aaf79003374a68dbb05926437ed305cf2a8ec96
Reviewed-on: https://go-review.googlesource.com/c/go/+/221602
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Robert Griesemer 2020-02-10 22:02:47 -08:00
parent 17e6252c05
commit bfb903f252
5 changed files with 42 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
src/cmd/compile/internal/syntax/scanner.go
View File

@ -385,7 +385,7 @@ func (s *scanner) isIdentRune(c rune, first bool) bool {
s.errorf("identifier cannot begin with digit %#U", c) s.errorf("identifier cannot begin with digit %#U", c)
} }
case c >= utf8.RuneSelf: case c >= utf8.RuneSelf:
s.errorf("invalid identifier character %#U", c) s.errorf("invalid character %#U in identifier", c)
default: default:
return false return false
} }
@ -612,13 +612,13 @@ func (s *scanner) rune() {
if r == '\n' { if r == '\n' {
s.ungetr() // assume newline is not part of literal s.ungetr() // assume newline is not part of literal
if !s.bad { if !s.bad {
s.errorf("newline in character literal") s.errorf("newline in rune literal")
} }
break break
} }
if r < 0 { if r < 0 {
if !s.bad { if !s.bad {
s.errorAtf(0, "invalid character literal (missing closing ')") s.errorAtf(0, "rune literal not terminated")
} }
break break
} }
@ -626,9 +626,9 @@ func (s *scanner) rune() {
if !s.bad { if !s.bad {
if n == 0 { if n == 0 {
s.errorf("empty character literal or unescaped ' in character literal") s.errorf("empty rune literal or unescaped '")
} else if n != 1 { } else if n != 1 {
s.errorAtf(0, "invalid character literal (more than one character)") s.errorAtf(0, "more than one character in rune literal")
} }
} }
@ -815,7 +815,7 @@ func (s *scanner) escape(quote rune) {
if c < 0 { if c < 0 {
return // complain in caller about EOF return // complain in caller about EOF
} }
s.errorf("unknown escape sequence") s.errorf("unknown escape")
return return
} }
@ -836,7 +836,7 @@ func (s *scanner) escape(quote rune) {
if base == 8 { if base == 8 {
kind = "octal" kind = "octal"
} }
s.errorf("non-%s character in escape sequence: %c", kind, c) s.errorf("invalid character %q in %s escape", c, kind)
s.ungetr() s.ungetr()
return return
} }
@ -847,11 +847,11 @@ func (s *scanner) escape(quote rune) {
s.ungetr() s.ungetr()
if x > max && base == 8 { if x > max && base == 8 {
s.errorf("octal escape value > 255: %d", x) s.errorf("octal escape value %d > 255", x)
return return
} }
if x > max || 0xD800 <= x && x < 0xE000 /* surrogate range */ { if x > max || 0xD800 <= x && x < 0xE000 /* surrogate range */ {
s.errorf("escape sequence is invalid Unicode code point %#U", x) s.errorf("escape is invalid Unicode code point %#U", x)
} }
} }

54
src/cmd/compile/internal/syntax/scanner_test.go
View File

@ -596,10 +596,10 @@ func TestScanErrors(t *testing.T) {
{"foo\n\n\xff ", "invalid UTF-8 encoding", 2, 0}, {"foo\n\n\xff ", "invalid UTF-8 encoding", 2, 0},
// token-level errors // token-level errors
{"\u00BD" /* ½ */, "invalid identifier character U+00BD '½'", 0, 0}, {"\u00BD" /* ½ */, "invalid character U+00BD '½' in identifier", 0, 0},
{"\U0001d736\U0001d737\U0001d738_½" /* 𝜶𝜷𝜸_½ */, "invalid identifier character U+00BD '½'", 0, 13 /* byte offset */}, {"\U0001d736\U0001d737\U0001d738_½" /* 𝜶𝜷𝜸_½ */, "invalid character U+00BD '½' in identifier", 0, 13 /* byte offset */},
{"\U0001d7d8" /* 𝟘 */, "identifier cannot begin with digit U+1D7D8 '𝟘'", 0, 0}, {"\U0001d7d8" /* 𝟘 */, "identifier cannot begin with digit U+1D7D8 '𝟘'", 0, 0},
{"foo\U0001d7d8_½" /* foo𝟘_½ */, "invalid identifier character U+00BD '½'", 0, 8 /* byte offset */}, {"foo\U0001d7d8_½" /* foo𝟘_½ */, "invalid character U+00BD '½' in identifier", 0, 8 /* byte offset */},
{"x + ~y", "invalid character U+007E '~'", 0, 4}, {"x + ~y", "invalid character U+007E '~'", 0, 4},
{"foo$bar = 0", "invalid character U+0024 '$'", 0, 3}, {"foo$bar = 0", "invalid character U+0024 '$'", 0, 3},
@ -608,20 +608,20 @@ func TestScanErrors(t *testing.T) {
{"0123456789e0 /*\nfoobar", "comment not terminated", 0, 13}, // valid float constant {"0123456789e0 /*\nfoobar", "comment not terminated", 0, 13}, // valid float constant
{"var a, b = 09, 07\n", "invalid digit '9' in octal literal", 0, 12}, {"var a, b = 09, 07\n", "invalid digit '9' in octal literal", 0, 12},
{`''`, "empty character literal or unescaped ' in character literal", 0, 1}, {`''`, "empty rune literal or unescaped '", 0, 1},
{"'\n", "newline in character literal", 0, 1}, {"'\n", "newline in rune literal", 0, 1},
{`'\`, "invalid character literal (missing closing ')", 0, 0}, {`'\`, "rune literal not terminated", 0, 0},
{`'\'`, "invalid character literal (missing closing ')", 0, 0}, {`'\'`, "rune literal not terminated", 0, 0},
{`'\x`, "invalid character literal (missing closing ')", 0, 0}, {`'\x`, "rune literal not terminated", 0, 0},
{`'\x'`, "non-hex character in escape sequence: '", 0, 3}, {`'\x'`, "invalid character '\\'' in hex escape", 0, 3},
{`'\y'`, "unknown escape sequence", 0, 2}, {`'\y'`, "unknown escape", 0, 2},
{`'\x0'`, "non-hex character in escape sequence: '", 0, 4}, {`'\x0'`, "invalid character '\\'' in hex escape", 0, 4},
{`'\00'`, "non-octal character in escape sequence: '", 0, 4}, {`'\00'`, "invalid character '\\'' in octal escape", 0, 4},
{`'\377' /*`, "comment not terminated", 0, 7}, // valid octal escape {`'\377' /*`, "comment not terminated", 0, 7}, // valid octal escape
{`'\378`, "non-octal character in escape sequence: 8", 0, 4}, {`'\378`, "invalid character '8' in octal escape", 0, 4},
{`'\400'`, "octal escape value > 255: 256", 0, 5}, {`'\400'`, "octal escape value 256 > 255", 0, 5},
{`'xx`, "invalid character literal (missing closing ')", 0, 0}, {`'xx`, "rune literal not terminated", 0, 0},
{`'xx'`, "invalid character literal (more than one character)", 0, 0}, {`'xx'`, "more than one character in rune literal", 0, 0},
{"\n \"foo\n", "newline in string", 1, 7}, {"\n \"foo\n", "newline in string", 1, 7},
{`"`, "string not terminated", 0, 0}, {`"`, "string not terminated", 0, 0},
@ -633,20 +633,20 @@ func TestScanErrors(t *testing.T) {
{`"\`, "string not terminated", 0, 0}, {`"\`, "string not terminated", 0, 0},
{`"\"`, "string not terminated", 0, 0}, {`"\"`, "string not terminated", 0, 0},
{`"\x`, "string not terminated", 0, 0}, {`"\x`, "string not terminated", 0, 0},
{`"\x"`, "non-hex character in escape sequence: \"", 0, 3}, {`"\x"`, "invalid character '\"' in hex escape", 0, 3},
{`"\y"`, "unknown escape sequence", 0, 2}, {`"\y"`, "unknown escape", 0, 2},
{`"\x0"`, "non-hex character in escape sequence: \"", 0, 4}, {`"\x0"`, "invalid character '\"' in hex escape", 0, 4},
{`"\00"`, "non-octal character in escape sequence: \"", 0, 4}, {`"\00"`, "invalid character '\"' in octal escape", 0, 4},
{`"\377" /*`, "comment not terminated", 0, 7}, // valid octal escape {`"\377" /*`, "comment not terminated", 0, 7}, // valid octal escape
{`"\378"`, "non-octal character in escape sequence: 8", 0, 4}, {`"\378"`, "invalid character '8' in octal escape", 0, 4},
{`"\400"`, "octal escape value > 255: 256", 0, 5}, {`"\400"`, "octal escape value 256 > 255", 0, 5},
{`s := "foo\z"`, "unknown escape sequence", 0, 10}, {`s := "foo\z"`, "unknown escape", 0, 10},
{`s := "foo\z00\nbar"`, "unknown escape sequence", 0, 10}, {`s := "foo\z00\nbar"`, "unknown escape", 0, 10},
{`"\x`, "string not terminated", 0, 0}, {`"\x`, "string not terminated", 0, 0},
{`"\x"`, "non-hex character in escape sequence: \"", 0, 3}, {`"\x"`, "invalid character '\"' in hex escape", 0, 3},
{`var s string = "\x"`, "non-hex character in escape sequence: \"", 0, 18}, {`var s string = "\x"`, "invalid character '\"' in hex escape", 0, 18},
{`return "\Uffffffff"`, "escape sequence is invalid Unicode code point U+FFFFFFFF", 0, 18}, {`return "\Uffffffff"`, "escape is invalid Unicode code point U+FFFFFFFF", 0, 18},
{"0b.0", "invalid radix point in binary literal", 0, 2}, {"0b.0", "invalid radix point in binary literal", 0, 2},
{"0x.p0\n", "hexadecimal literal has no digits", 0, 3}, {"0x.p0\n", "hexadecimal literal has no digits", 0, 3},

2
test/fixedbugs/bug169.go
View File

@ -5,6 +5,6 @@
// license that can be found in the LICENSE file. // license that can be found in the LICENSE file.
package main package main
var x = '''; // ERROR "char" var x = '''; // ERROR "char|rune"

8
test/fixedbugs/issue15611.go
View File

@ -8,13 +8,13 @@ package p
// These error messages are for the invalid literals on lines 19 and 20: // These error messages are for the invalid literals on lines 19 and 20:
// ERROR "newline in character literal" // ERROR "newline in character literal|newline in rune literal"
// ERROR "invalid character literal \(missing closing '\)" // ERROR "invalid character literal \(missing closing '\)|rune literal not terminated"
const ( const (
_ = '' // ERROR "empty character literal or unescaped ' in character literal" _ = '' // ERROR "empty character literal or unescaped ' in character literal|empty rune literal"
_ = 'f' _ = 'f'
_ = 'foo' // ERROR "invalid character literal \(more than one character\)" _ = 'foo' // ERROR "invalid character literal \(more than one character\)|more than one character in rune literal"
//line issue15611.go:11 //line issue15611.go:11
_ = ' _ = '
_ = ' _ = '

2
test/fixedbugs/issue32133.go
View File

@ -8,7 +8,7 @@ package p
// errors for the //line-adjusted code below // errors for the //line-adjusted code below
// ERROR "newline in string" // ERROR "newline in string"
// ERROR "newline in character literal" // ERROR "newline in character literal|newline in rune literal"
// ERROR "newline in string" // ERROR "newline in string"
// ERROR "string not terminated" // ERROR "string not terminated"