cmd/compile, go/parser: simpler binary expression parsing

The existing nested loops are too tricky for me to grok and don't seem
necessary.

Change-Id: I75c65c8470b799d6f4cfb05bb1b4796c5d7d32e7
Reviewed-on: https://go-review.googlesource.com/19927
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 11 insertions, 15 deletions

diff --git a/src/go/parser/parser.go b/src/go/parser/parser.go
index f3a26032ee..d3ef7db31e 100644
--- a/src/go/parser/parser.go
+++ b/src/go/parser/parser.go
@@ -1597,23 +1597,19 @@ func (p *parser) parseBinaryExpr(lhs bool, prec1 int) ast.Expr {
 	}
 
 	x := p.parseUnaryExpr(lhs)
-	for _, prec := p.tokPrec(); prec >= prec1; prec-- {
-		for {
-			op, oprec := p.tokPrec()
-			if oprec != prec {
-				break
-			}
-			pos := p.expect(op)
-			if lhs {
-				p.resolve(x)
-				lhs = false
-			}
-			y := p.parseBinaryExpr(false, prec+1)
-			x = &ast.BinaryExpr{X: p.checkExpr(x), OpPos: pos, Op: op, Y: p.checkExpr(y)}
+	for {
+		op, oprec := p.tokPrec()
+		if oprec < prec1 {
+			return x
+		}
+		pos := p.expect(op)
+		if lhs {
+			p.resolve(x)
+			lhs = false
 		}
+		y := p.parseBinaryExpr(false, oprec+1)
+		x = &ast.BinaryExpr{X: p.checkExpr(x), OpPos: pos, Op: op, Y: p.checkExpr(y)}
 	}
-
-	return x
 }
 
 // If lhs is set and the result is an identifier, it is not resolved.