go/parser: better error (recovery) for Allman/BSD-style func decls

This matches the behavior and error of cmd/compile.

Fixes #34946.

Change-Id: I329ef358deea63d8425f76f1d54c95749b96c365
Reviewed-on: https://go-review.googlesource.com/c/go/+/202484
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/go/parser/parser.go b/src/go/parser/parser.go
index ba16b652246f11bcae4c99e21ca29420fb830f53..35349611e8b7318bac247dcaa77fbad874211468 100644 (file)
--- a/src/go/parser/parser.go
+++ b/src/go/parser/parser.go
@@ -2439,8 +2439,18 @@ func (p *parser) parseFuncDecl() *ast.FuncDecl {
        var body *ast.BlockStmt
        if p.tok == token.LBRACE {
                body = p.parseBody(scope)
+               p.expectSemi()
+       } else if p.tok == token.SEMICOLON {
+               p.next()
+               if p.tok == token.LBRACE {
+                       // opening { of function declaration on next line
+                       p.error(p.pos, "unexpected semicolon or newline before {")
+                       body = p.parseBody(scope)
+                       p.expectSemi()
+               }
+       } else {
+               p.expectSemi()
        }
-       p.expectSemi()
 
        decl := &ast.FuncDecl{
                Doc:  doc,

diff --git a/src/go/parser/testdata/issue34946.src b/src/go/parser/testdata/issue34946.src
new file mode 100644 (file)
index 0000000..6bb15e1
--- /dev/null
+++ b/src/go/parser/testdata/issue34946.src
@@ -0,0 +1,22 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test case for issue 34946: Better synchronization of
+// parser for function declarations that start their
+// body's opening { on a new line.
+
+package p
+
+// accept Allman/BSD-style declaration but complain
+// (implicit semicolon between signature and body)
+func _() int
+{ /* ERROR "unexpected semicolon or newline before {" */
+       { return 0 }
+}
+
+func _() {}
+
+func _(); { /* ERROR "unexpected semicolon or newline before {" */ }
+
+func _() {}