cmd/compile: handle pragmas immediately with -newparser=1

Instead of saving all pragmas and processing them after parsing is
finished, process them immediately during scanning like the current
lexer does.

This is a bit unfortunate because it means we can't use
syntax.ParseFile to concurrently parse files yet, but it fixes how we
report syntax errors in the presence of //line pragmas.

While here, add a bunch more gcCompat entries to syntax/parser.go to
get "go build -toolexec='toolstash -cmp' std cmd" passing. There are
still a few remaining cases only triggered building unit tests, but
this seems like a nice checkpoint.

Change-Id: Iaf3bbcf2849857a460496f31eea228e0c585ce13
Reviewed-on: https://go-review.googlesource.com/28226
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 9 insertions, 6 deletions

diff --git a/src/cmd/compile/internal/syntax/scanner.go b/src/cmd/compile/internal/syntax/scanner.go
index d02bb6d11b..e78950ad1a 100644
--- a/src/cmd/compile/internal/syntax/scanner.go
+++ b/src/cmd/compile/internal/syntax/scanner.go
@@ -15,6 +15,7 @@ import (
 type scanner struct {
 	source
 	nlsemi bool // if set '\n' and EOF translate to ';'
+	pragma Pragma
 
 	// current token, valid after calling next()
 	pos, line int
@@ -24,12 +25,13 @@ type scanner struct {
 	op        Operator // valid if tok is _Operator, _AssignOp, or _IncOp
 	prec      int      // valid if tok is _Operator, _AssignOp, or _IncOp
 
-	pragmas []Pragma
+	pragh PragmaHandler
 }
 
-func (s *scanner) init(src io.Reader, errh ErrorHandler) {
+func (s *scanner) init(src io.Reader, errh ErrorHandler, pragh PragmaHandler) {
 	s.source.init(src, errh)
 	s.nlsemi = false
+	s.pragh = pragh
 }
 
 func (s *scanner) next() {
@@ -540,6 +542,10 @@ func (s *scanner) lineComment() {
 	// recognize pragmas
 	var prefix string
 	r := s.getr()
+	if s.pragh == nil {
+		goto skip
+	}
+
 	switch r {
 	case 'g':
 		prefix = "go:"
@@ -565,10 +571,7 @@ func (s *scanner) lineComment() {
 		}
 		r = s.getr()
 	}
-	s.pragmas = append(s.pragmas, Pragma{
-		Line: s.line,
-		Text: strings.TrimSuffix(string(s.stopLit()), "\r"),
-	})
+	s.pragma |= s.pragh(0, s.line, strings.TrimSuffix(string(s.stopLit()), "\r"))
 	return
 
 skip: