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cmd/compile/internal/syntax: differentiate between ';' and '\n' in syntax errors
Towards better syntax error messages: With this change, the parser knows whether a semicolon was an actual ';' in the source, or whether it was an automatically inserted semicolon as result of a '\n' or EOF. Using this information in error messages makes them more understandable. For #17328. Change-Id: I8cd9accee8681b62569d0ecef922d38682b401eb Reviewed-on: https://go-review.googlesource.com/36636 Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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@ -144,7 +144,7 @@ func (p *parser) syntax_error_at(pos src.Pos, msg string) {
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// determine token string
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var tok string
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switch p.tok {
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case _Name:
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case _Name, _Semi:
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tok = p.lit
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case _Literal:
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tok = "literal " + p.lit
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@ -215,7 +215,7 @@ func tokstring(tok token) string {
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case _Comma:
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return "comma"
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case _Semi:
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return "semicolon or newline"
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return "semicolon"
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}
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return tok.String()
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}
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@ -27,7 +27,7 @@ type scanner struct {
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// current token, valid after calling next()
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line, col uint
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tok token
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lit string // valid if tok is _Name or _Literal
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lit string // valid if tok is _Name, _Literal, or _Semi ("semicolon", "newline", or "EOF")
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kind LitKind // valid if tok is _Literal
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op Operator // valid if tok is _Operator, _AssignOp, or _IncOp
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prec int // valid if tok is _Operator, _AssignOp, or _IncOp
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@ -73,12 +73,14 @@ redo:
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switch c {
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case -1:
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if nlsemi {
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s.lit = "EOF"
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s.tok = _Semi
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break
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}
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s.tok = _EOF
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case '\n':
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s.lit = "newline"
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s.tok = _Semi
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case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
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@ -106,6 +108,7 @@ redo:
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s.tok = _Comma
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case ';':
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s.lit = "semicolon"
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s.tok = _Semi
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case ')':
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@ -185,6 +188,7 @@ redo:
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if s.source.line > s.line && nlsemi {
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// A multi-line comment acts like a newline;
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// it translates to a ';' if nlsemi is set.
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s.lit = "newline"
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s.tok = _Semi
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break
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}
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@ -66,6 +66,11 @@ func TestTokens(t *testing.T) {
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}
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switch want.tok {
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case _Semi:
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if got.lit != "semicolon" {
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t.Errorf("got %s; want semicolon", got.lit)
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}
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case _Name, _Literal:
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if got.lit != want.src {
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t.Errorf("got lit = %q; want %q", got.lit, want.src)
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@ -94,6 +99,9 @@ func TestTokens(t *testing.T) {
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t.Errorf("got tok = %s; want ;", got.tok)
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continue
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}
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if got.lit != "newline" {
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t.Errorf("got %s; want newline", got.lit)
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}
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}
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got.next()
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@ -9,6 +9,6 @@ package f
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import /* // ERROR "import path" */ `
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bogus`
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func f(x int /* // ERROR "unexpected semicolon"
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func f(x int /* // ERROR "unexpected newline"
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*/)
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@ -6,6 +6,6 @@
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package main
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type T // ERROR "unexpected semicolon or newline in type declaration"
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// line below uncommented to avoid follow-up error
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// {
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type T1 // ERROR "unexpected newline in type declaration"
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type T2 /* // ERROR "unexpected EOF in type declaration" */
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