From: Rob Findley <rfindley@google.com>
Date: Wed, 17 Mar 2021 16:42:19 +0000 (-0400)
Subject: go/parser: avoid formatting a panic message if an assertion succeeds
X-Git-Tag: go1.17beta1~1084
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=0bd308ff27822378dc2db77d6dd0ad3c15ed2e08;p=gostls13.git

go/parser: avoid formatting a panic message if an assertion succeeds

tryResolve is an extremely hot method on the parser. Eliminating this
formatting led to a 20% performance improvement in BenchmarkParse.

Change-Id: Idf8850404bd72d45d1351356427a85086422ea68
Reviewed-on: https://go-review.googlesource.com/c/go/+/302629
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
---

diff --git a/src/go/parser/parser.go b/src/go/parser/parser.go
index ed1867b3b3..b86d6bad46 100644
--- a/src/go/parser/parser.go
+++ b/src/go/parser/parser.go
@@ -181,7 +181,10 @@ func (p *parser) tryResolve(x ast.Expr, collectUnresolved bool) {
 	if ident == nil {
 		return
 	}
-	assert(ident.Obj == nil, fmt.Sprintf("identifier %s already declared or resolved", ident.Name))
+	// Don't use assert here, to avoid needless formatting of the message below.
+	if ident.Obj != nil {
+		panic(fmt.Sprintf("identifier %s already declared or resolved", ident.Name))
+	}
 	if ident.Name == "_" {
 		return
 	}