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, 16 insertions, 6 deletions

diff --git a/src/cmd/compile/internal/syntax/syntax.go b/src/cmd/compile/internal/syntax/syntax.go
index 85dddaa47f..6c0abd118d 100644
--- a/src/cmd/compile/internal/syntax/syntax.go
+++ b/src/cmd/compile/internal/syntax/syntax.go
@@ -12,17 +12,27 @@ import (
 
 type Mode uint
 
+// A Pragma value is a set of flags that augment a function
+// declaration. Callers may assign meaning to the flags as
+// appropriate.
+type Pragma uint16
+
 type ErrorHandler func(pos, line int, msg string)
 
+// A PragmaHandler is used to process //line and //go: directives as
+// they're scanned. The returned Pragma value will be unioned into the
+// next FuncDecl node.
+type PragmaHandler func(pos, line int, text string) Pragma
+
 // TODO(gri) These need a lot more work.
 
-func ReadFile(filename string, errh ErrorHandler, mode Mode) (*File, error) {
+func ReadFile(filename string, errh ErrorHandler, pragh PragmaHandler, mode Mode) (*File, error) {
 	src, err := os.Open(filename)
 	if err != nil {
 		return nil, err
 	}
 	defer src.Close()
-	return Read(src, errh, mode)
+	return Read(src, errh, pragh, mode)
 }
 
 type bytesReader struct {
@@ -38,13 +48,13 @@ func (r *bytesReader) Read(p []byte) (int, error) {
 	return 0, io.EOF
 }
 
-func ReadBytes(src []byte, errh ErrorHandler, mode Mode) (*File, error) {
-	return Read(&bytesReader{src}, errh, mode)
+func ReadBytes(src []byte, errh ErrorHandler, pragh PragmaHandler, mode Mode) (*File, error) {
+	return Read(&bytesReader{src}, errh, pragh, mode)
 }
 
-func Read(src io.Reader, errh ErrorHandler, mode Mode) (*File, error) {
+func Read(src io.Reader, errh ErrorHandler, pragh PragmaHandler, mode Mode) (*File, error) {
 	var p parser
-	p.init(src, errh)
+	p.init(src, errh, pragh)
 
 	p.next()
 	ast := p.file()