diff --git a/src/go/parser/parser.go b/src/go/parser/parser.go
index bee5ed064c8a512b40f3239b9824ce0fc7822c8f..6f2955fd509000da9c093718be1a2da09e8f042d 100644
--- a/src/go/parser/parser.go
+++ b/src/go/parser/parser.go
@@ -48,11 +48,11 @@ type parser struct {
lit string // token literal
// Error recovery
- // (used to limit the number of calls to syncXXX functions
+ // (used to limit the number of calls to parser.advance
// w/o making scanning progress - avoids potential endless
// loops across multiple parser functions during error recovery)
syncPos token.Pos // last synchronization position
- syncCnt int // number of calls to syncXXX without progress
+ syncCnt int // number of parser.advance calls without progress
// Non-syntactic parser control
exprLev int // < 0: in control clause, >= 0: in expression
@@ -419,7 +419,7 @@ func (p *parser) expectSemi() {
p.next()
default:
p.errorExpected(p.pos, "';'")
- p.syncStmt()
+ p.advance(stmtStart)
}
}
}
@@ -445,23 +445,16 @@ func assert(cond bool, msg string) {
}
}
-// TODO(gri) The syncX methods below all use the same pattern. Factor.
-
-// syncStmt advances to the next statement.
-// Used for synchronization after an error.
-//
-func (p *parser) syncStmt() {
- for {
- switch p.tok {
- case token.BREAK, token.CONST, token.CONTINUE, token.DEFER,
- token.FALLTHROUGH, token.FOR, token.GO, token.GOTO,
- token.IF, token.RETURN, token.SELECT, token.SWITCH,
- token.TYPE, token.VAR:
+// advance consumes tokens until the current token p.tok
+// is in the 'to' set, or token.EOF. For error recovery.
+func (p *parser) advance(to map[token.Token]bool) {
+ for ; p.tok != token.EOF; p.next() {
+ if to[p.tok] {
// Return only if parser made some progress since last
- // sync or if it has not reached 10 sync calls without
+ // sync or if it has not reached 10 advance calls without
// progress. Otherwise consume at least one token to
// avoid an endless parser loop (it is possible that
- // both parseOperand and parseStmt call syncStmt and
+ // both parseOperand and parseStmt call advance and
// correctly do not advance, thus the need for the
// invocation limit p.syncCnt).
if p.pos == p.syncPos && p.syncCnt < 10 {
@@ -478,59 +471,40 @@ func (p *parser) syncStmt() {
// leads to skipping of possibly correct code if a
// previous error is present, and thus is preferred
// over a non-terminating parse.
- case token.EOF:
- return
}
- p.next()
}
}
-// syncDecl advances to the next declaration.
-// Used for synchronization after an error.
-//
-func (p *parser) syncDecl() {
- for {
- switch p.tok {
- case token.CONST, token.TYPE, token.VAR:
- // see comments in syncStmt
- if p.pos == p.syncPos && p.syncCnt < 10 {
- p.syncCnt++
- return
- }
- if p.pos > p.syncPos {
- p.syncPos = p.pos
- p.syncCnt = 0
- return
- }
- case token.EOF:
- return
- }
- p.next()
- }
+var stmtStart = map[token.Token]bool{
+ token.BREAK: true,
+ token.CONST: true,
+ token.CONTINUE: true,
+ token.DEFER: true,
+ token.FALLTHROUGH: true,
+ token.FOR: true,
+ token.GO: true,
+ token.GOTO: true,
+ token.IF: true,
+ token.RETURN: true,
+ token.SELECT: true,
+ token.SWITCH: true,
+ token.TYPE: true,
+ token.VAR: true,
}
-// syncExprEnd advances to the likely end of an expression.
-// Used for synchronization after an error.
-//
-func (p *parser) syncExprEnd() {
- for {
- switch p.tok {
- case token.COMMA, token.COLON, token.SEMICOLON, token.RPAREN, token.RBRACK, token.RBRACE:
- // see comments in syncStmt
- if p.pos == p.syncPos && p.syncCnt < 10 {
- p.syncCnt++
- return
- }
- if p.pos > p.syncPos {
- p.syncPos = p.pos
- p.syncCnt = 0
- return
- }
- case token.EOF:
- return
- }
- p.next()
- }
+var declStart = map[token.Token]bool{
+ token.CONST: true,
+ token.TYPE: true,
+ token.VAR: true,
+}
+
+var exprEnd = map[token.Token]bool{
+ token.COMMA: true,
+ token.COLON: true,
+ token.SEMICOLON: true,
+ token.RPAREN: true,
+ token.RBRACK: true,
+ token.RBRACE: true,
}
// safePos returns a valid file position for a given position: If pos
@@ -649,7 +623,7 @@ func (p *parser) parseType() ast.Expr {
if typ == nil {
pos := p.pos
p.errorExpected(pos, "type")
- p.syncExprEnd()
+ p.advance(exprEnd)
return &ast.BadExpr{From: pos, To: p.pos}
}
@@ -1192,7 +1166,7 @@ func (p *parser) parseOperand(lhs bool) ast.Expr {
// we have an error
pos := p.pos
p.errorExpected(pos, "operand")
- p.syncStmt()
+ p.advance(stmtStart)
return &ast.BadExpr{From: pos, To: p.pos}
}
@@ -2228,7 +2202,7 @@ func (p *parser) parseStmt() (s ast.Stmt) {
switch p.tok {
case token.CONST, token.TYPE, token.VAR:
- s = &ast.DeclStmt{Decl: p.parseDecl((*parser).syncStmt)}
+ s = &ast.DeclStmt{Decl: p.parseDecl(stmtStart)}
case
// tokens that may start an expression
token.IDENT, token.INT, token.FLOAT, token.IMAG, token.CHAR, token.STRING, token.FUNC, token.LPAREN, // operands
@@ -2273,7 +2247,7 @@ func (p *parser) parseStmt() (s ast.Stmt) {
// no statement found
pos := p.pos
p.errorExpected(pos, "statement")
- p.syncStmt()
+ p.advance(stmtStart)
s = &ast.BadStmt{From: pos, To: p.pos}
}
@@ -2487,7 +2461,7 @@ func (p *parser) parseFuncDecl() *ast.FuncDecl {
return decl
}
-func (p *parser) parseDecl(sync func(*parser)) ast.Decl {
+func (p *parser) parseDecl(sync map[token.Token]bool) ast.Decl {
if p.trace {
defer un(trace(p, "Declaration"))
}
@@ -2506,7 +2480,7 @@ func (p *parser) parseDecl(sync func(*parser)) ast.Decl {
default:
pos := p.pos
p.errorExpected(pos, "declaration")
- sync(p)
+ p.advance(sync)
return &ast.BadDecl{From: pos, To: p.pos}
}
@@ -2556,7 +2530,7 @@ func (p *parser) parseFile() *ast.File {
if p.mode&ImportsOnly == 0 {
// rest of package body
for p.tok != token.EOF {
- decls = append(decls, p.parseDecl((*parser).syncDecl))
+ decls = append(decls, p.parseDecl(declStart))
}
}
}