go/parser, go/ast: correctly take into account presence of } in block

Correctly track whether the closing } of a block (or a function body)
is present or not in the AST and report correct End() positions in
each case.

There are more cases like this but this CL addresses an immediate
issue and sets a precedent for how to fix similar cases if a need
arises.

Fixes #33649.

Change-Id: Id6662ddaac09f3c15f8003edc9275fe2b0c41c78
Reviewed-on: https://go-review.googlesource.com/c/go/+/202581
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/src/go/parser/parser.go b/src/go/parser/parser.go
index 3a468d096b..beb563f25f 100644
--- a/src/go/parser/parser.go
+++ b/src/go/parser/parser.go
@@ -397,6 +397,18 @@ func (p *parser) expect(tok token.Token) token.Pos {
 	return pos
 }
 
+// expect2 is like expect, but it returns an invalid position
+// if the expected token is not found.
+func (p *parser) expect2(tok token.Token) (pos token.Pos) {
+	if p.tok == tok {
+		pos = p.pos
+	} else {
+		p.errorExpected(pos, "'"+tok.String()+"'")
+	}
+	p.next() // make progress
+	return
+}
+
 // expectClosing is like expect but provides a better error message
 // for the common case of a missing comma before a newline.
 //
@@ -1082,7 +1094,7 @@ func (p *parser) parseBody(scope *ast.Scope) *ast.BlockStmt {
 	list := p.parseStmtList()
 	p.closeLabelScope()
 	p.closeScope()
-	rbrace := p.expect(token.RBRACE)
+	rbrace := p.expect2(token.RBRACE)
 
 	return &ast.BlockStmt{Lbrace: lbrace, List: list, Rbrace: rbrace}
 }
@@ -1096,7 +1108,7 @@ func (p *parser) parseBlockStmt() *ast.BlockStmt {
 	p.openScope()
 	list := p.parseStmtList()
 	p.closeScope()
-	rbrace := p.expect(token.RBRACE)
+	rbrace := p.expect2(token.RBRACE)
 
 	return &ast.BlockStmt{Lbrace: lbrace, List: list, Rbrace: rbrace}
 }