syntax: recover binary commands properly

I wasn't paying close enough attention to the code;
the returned statement is the parent containing both branches,
not just the right branch which is recovered.

Teach the tests to spot when the result is empty or all recovered,
which caught these mistakes.

syntax/parser.go

@@ -1721,10 +1721,11 @@ func (p *Parser) getStmt(readEnd, binCmd, fnBody bool) *Stmt {
 		b.Y = p.getStmt(false, true, false)
 		if b.Y == nil || p.err != nil {
 			if p.recoverError() {
-				return &Stmt{Position: recoveredPos}
+				b.Y = &Stmt{Position: recoveredPos}
+			} else {
+				p.followErr(b.OpPos, b.Op.String(), "a statement")
+				return nil
 			}
-			p.followErr(b.OpPos, b.Op.String(), "a statement")
-			return nil
 		}
 		s = &Stmt{Position: s.Position}
 		s.Cmd = b
@@ -1897,10 +1898,11 @@ func (p *Parser) gotStmtPipe(s *Stmt, binCmd bool) *Stmt {
 		p.got(_Newl)
 		if b.Y = p.gotStmtPipe(&Stmt{Position: p.pos}, true); b.Y == nil || p.err != nil {
 			if p.recoverError() {
-				return &Stmt{Position: recoveredPos}
+				b.Y = &Stmt{Position: recoveredPos}
+			} else {
+				p.followErr(b.OpPos, b.Op.String(), "a statement")
+				break
 			}
-			p.followErr(b.OpPos, b.Op.String(), "a statement")
-			break
 		}
 		s = &Stmt{Position: s.Position}
 		s.Cmd = b

syntax/parser_test.go

@@ -2618,12 +2618,21 @@ func TestParseRecoverErrors(t *testing.T) {
 	printer := NewPrinter()
 	for _, tc := range tests {
 		t.Run("", func(t *testing.T) {
+			t.Logf("input: %s", tc.src)
 			r := strings.NewReader(tc.src)
 			f, err := parser.Parse(r, "")
 			if tc.wantErr {
 				qt.Assert(t, qt.Not(qt.IsNil(err)))
 			} else {
 				qt.Assert(t, qt.IsNil(err))
+				switch len(f.Stmts) {
+				case 0:
+					t.Fatalf("result has no statements")
+				case 1:
+					if f.Stmts[0].Pos().IsRecovered() {
+						t.Fatalf("result is only a recovered statement")
+					}
+				}
 			}
 			qt.Assert(t, qt.Equals(countRecoveredPositions(reflect.ValueOf(f)), tc.wantMissing))