Reviewers: iant,
Message:
Hello [email protected] (cc: [email protected]),
I'd like you to review this change to
https://code.google.com/p/go
Description:
go/ast: track position of <- for channel types
This is a backward-compatible API change.
Without the correct <- position information,
certain channel types have incorrect position
information.
Please review this at http://codereview.appspot.com/6585063/
Affected files:
M src/pkg/go/ast/ast.go
M src/pkg/go/parser/parser.go
M src/pkg/go/parser/short_test.go
M src/pkg/go/printer/nodes.go
Index: src/pkg/go/ast/ast.go
===================================================================
--- a/src/pkg/go/ast/ast.go
+++ b/src/pkg/go/ast/ast.go
@@ -407,6 +407,7 @@
// A ChanType node represents a channel type.
ChanType struct {
Begin token.Pos // position of "chan" keyword or "<-" (whichever comes
first)
+ Arrow token.Pos // position of "<-" (noPos if there is no "<-")
Dir ChanDir // channel direction
Value Expr // value type
}
Index: src/pkg/go/parser/parser.go
===================================================================
--- a/src/pkg/go/parser/parser.go
+++ b/src/pkg/go/parser/parser.go
@@ -924,20 +924,22 @@
pos := p.pos
dir := ast.SEND | ast.RECV
+ var arrow token.Pos
if p.tok == token.CHAN {
p.next()
if p.tok == token.ARROW {
+ arrow = p.pos
p.next()
dir = ast.SEND
}
} else {
- p.expect(token.ARROW)
+ arrow = p.expect(token.ARROW)
p.expect(token.CHAN)
dir = ast.RECV
}
value := p.parseType()
- return &ast.ChanType{Begin: pos, Dir: dir, Value: value}
+ return &ast.ChanType{Begin: pos, Arrow: arrow, Dir: dir, Value: value}
}
// If the result is an identifier, it is not resolved.
@@ -1397,7 +1399,7 @@
case token.ARROW:
// channel type or receive expression
- pos := p.pos
+ arrow := p.pos
p.next()
// If the next token is token.CHAN we still don't know if it
@@ -1421,29 +1423,25 @@
// (<-type)
// re-associate position info and <-
- arrow := true
- for ok && arrow {
- begin := typ.Begin
+ dir := ast.SEND
+ for ok && dir == ast.SEND {
if typ.Dir == ast.RECV {
// error: (<-type) is (<-(<-chan T))
- p.errorExpected(begin, "'chan'")
+ p.errorExpected(typ.Arrow, "'chan'")
}
- arrow = typ.Dir == ast.SEND
- typ.Begin = pos
- typ.Dir = ast.RECV
+ arrow, typ.Begin, typ.Arrow = typ.Arrow, arrow, arrow
+ dir, typ.Dir = typ.Dir, ast.RECV
typ, ok = typ.Value.(*ast.ChanType)
- // TODO(gri) ast.ChanType should store exact <- position
- pos = begin // estimate (we don't have the exact position of <- for
send channels)
}
- if arrow {
- p.errorExpected(pos, "'chan'")
+ if dir == ast.SEND {
+ p.errorExpected(arrow, "channel type")
}
return x
}
// <-(expr)
- return &ast.UnaryExpr{OpPos: pos, Op: token.ARROW, X: p.checkExpr(x)}
+ return &ast.UnaryExpr{OpPos: arrow, Op: token.ARROW, X: p.checkExpr(x)}
case token.MUL:
// pointer type or unary "*" expression
Index: src/pkg/go/parser/short_test.go
===================================================================
--- a/src/pkg/go/parser/short_test.go
+++ b/src/pkg/go/parser/short_test.go
@@ -69,7 +69,7 @@
`package p; var a = <- /* ERROR "expected expression" */ chan int;`,
`package p; func f() { select { case _ <- chan /* ERROR "expected
expression" */ int: } };`,
`package p; func f() { _ = (<-<- /* ERROR "expected 'chan'" */ chan
int)(nil) };`,
- `package p; func f() { _ = (<-chan<-chan<-chan<-chan<-chan /*
ERROR "expected 'chan'" */ <-int)(nil) };`,
+ `package p; func f() { _ = (<-chan<-chan<-chan<-chan<-chan<- /*
ERROR "expected channel type" */ int)(nil) };`,
}
func TestInvalid(t *testing.T) {
Index: src/pkg/go/printer/nodes.go
===================================================================
--- a/src/pkg/go/printer/nodes.go
+++ b/src/pkg/go/printer/nodes.go
@@ -853,9 +853,9 @@
case ast.SEND | ast.RECV:
p.print(token.CHAN)
case ast.RECV:
- p.print(token.ARROW, token.CHAN)
+ p.print(token.ARROW, token.CHAN) // x.Arrow and x.Pos() are the same
case ast.SEND:
- p.print(token.CHAN, token.ARROW)
+ p.print(token.CHAN, x.Arrow, token.ARROW)
}
p.print(blank)
p.expr(x.Value)
