if err != nil {
		t.Errorf("read error: %v", err)
	}
	if n != 0 {
		t.Errorf("wrong count; got %d want 0", n)
	}
}

func TestUnreadByte(t *testing.T) {
	b := new(Buffer)

	// check at EOF
	if err := b.UnreadByte(); err == nil {
		t.Fatal("UnreadByte at EOF: got no error")
	}
	if _, err := b.ReadByte(); err == nil {
		t.Fatal("ReadByte at EOF: got no error")
	}

				if err != nil {
					if !test.wantErr {
						t.Errorf("%s: %v", path, err)
					}
					sawErr = true
					return nil
				}
				files = append(files, path)
				return nil
			})
			if err != nil {
				t.Errorf("fs.WalkDir error: %v", err)
			}
			if test.wantErr && !sawErr {
				t.Error("succeeded but want error")

			parser.lineNum++
			if !parser.pseudo(test.pseudo, tokenize(test.operands)) {
				t.Fatalf("Wrong pseudo-instruction: %s", test.pseudo)
			}
			errorLine := buf.String()
			if test.expected != errorLine {
				t.Errorf("Unexpected error %q; expected %q", errorLine, test.expected)
			}
			buf.Reset()
		}
	}

			addr := obj.Addr{}
			parser.operand(&addr)
		})

		switch {
		case err == nil:
			t.Errorf("fail at %s: got no errors; expected %s\n", test.input, test.error)
		case !strings.Contains(err.Error(), test.error):
			t.Errorf("fail at %s: got %s; expected %s", test.input, err, test.error)
		}
	}
}

func testOperandParser(t *testing.T, parser *Parser, tests []operandTest) {
	for _, test := range tests {

	defer func() {
		if x := recover(); x != nil {
			t.Errorf("expected no panic; recovered %v", x)
		}
	}()

	testenv.MustHaveGoBuild(t)

	for _, context := range contexts {
		w := NewWalker(context, "testdata/src/issue64958")
		pkg, err := w.importFrom("p", "", 0)
		if err != nil {
			t.Errorf("expected no error importing; got %T", err)
		}
		w.export(pkg)
	}
}

	if err != nil {
		if list, ok := err.(scanner.ErrorList); ok {
			// If err is a scanner.ErrorList, its String will print just
			// the first error and then (+n more errors).
			// Instead, turn it into a new Error that will return
			// details for all the errors.
			for _, e := range list {
				fmt.Fprintln(os.Stderr, e)
			}
			os.Exit(2)
		}
		fatalf("parsing %s: %s", name, err)
	}
	return ast1
}

				time.Sleep(time.Millisecond)
				continue
			}

			t.Error(err)
			return
		}
		cmds = append(cmds, cmd)
	}

	failures := 0
	for _, cmd := range cmds {
		err := cmd.Wait()
		if err == nil {
			continue
		}

		t.Errorf("syscall.Exec failed: %v\n%s", err, cmd.Stdout)
		failures++
	}

	if failures > 0 {

This program will not compile, but cgo can use the presence or absence
of an error message on a given line to deduce the information it
needs. The program is syntactically valid regardless of whether each
name is a type or an ordinary identifier, so there will be no syntax
errors that might stop parsing early.

An error on not-declared:1 indicates that foo is undeclared.

</p>

<h2 id="Errors">Errors</h2>

<p>
The predeclared type <code>error</code> is defined as
</p>

<pre>
type error interface {
	Error() string
}
</pre>

<p>
It is the conventional interface for representing an error condition,
with the nil value representing no error.
For instance, a function to read data from a file might be defined:

    validations:
      required: false
  - type: textarea
    id: what-did-you-do
    attributes:
      label: "What did you do?"
      description: "If possible, provide a recipe for reproducing the error. Starting with a Private/Incognito tab/window may help rule out problematic browser extensions."
    validations:
      required: true
  - type: textarea
    id: actual-behavior
    attributes: