if as, ok := s.(*AssignStmt); ok && as.Op == 0 {
			// Emphasize complex Lhs and Rhs of assignment with parentheses to highlight '='.
			str = "assignment " + emphasize(as.Lhs) + " = " + emphasize(as.Rhs)
		} else {
			str = String(s)
		}
		p.syntaxErrorAt(s.Pos(), fmt.Sprintf("cannot use %s as value", str))
	}

	p.xnest = outer
	return
}

// emphasize returns a string representation of x, with (top-level)

@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault
// TODO(kevinb): I think we should push everything down to "BaseImmutableCollection" or something,
// just to do everything we can to emphasize the "practically an interface" nature of this class.
public abstract class ImmutableCollection<E> extends AbstractCollection<E> implements Serializable {
  /*

@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault
// TODO(kevinb): I think we should push everything down to "BaseImmutableCollection" or something,
// just to do everything we can to emphasize the "practically an interface" nature of this class.
public abstract class ImmutableCollection<E> extends AbstractCollection<E> implements Serializable {
  /*

    public enum Emphasis {
        BOLD, REVERSE, ITALIC
    }

    public enum Color {
        DEFAULT, YELLOW, RED, GREY, GREEN, BLACK
    }

    public final Set<Emphasis> emphasises;
    public final Color color;

    public Style(Set<Emphasis> emphasises, Color color) {
        this.emphasises = emphasises;
        this.color = color;
    }

        List<Color> colors = new ArrayList<Color>();
        for (Style.Emphasis emphasis : style.getEmphasises()) {
            if (emphasis.equals(Style.Emphasis.BOLD)) {
                colors.add(newBoldColor());
            } else if (emphasis.equals(Style.Emphasis.REVERSE)) {
                colors.add(newReverseColor());
            } else if (emphasis.equals(Style.Emphasis.ITALIC)) {
                colors.add(newItalicColor());
            }

    private static String expected(String text) {
        return emphatize(text, "blue");
    }

    private static String actual(String text) {
        return emphatize(text, "#ee442f");
    }

    private static String warning(String text) {
        return emphatize(text, "#c59434");
    }

    private static String grey(String text) {
        return emphatize(text, "#cccccc");
    }

        /**
         * General purpose success message
         */
        Success,
        /**
         * <b>Emphasized</b> success message
         */
        SuccessHeader,
        /**
         * General purpose failure message
         */
        Failure,
        /**
         * <b>Emphasized</b> failure message
         */
        FailureHeader,
        /**
         * General purpose informational text

	case '*', '~':
		// “A single * character can open emphasis iff
		// it is part of a left-flanking delimiter run.”

		// “A double ** can open strong emphasis iff
		// it is part of a left-flanking delimiter run.”
		canOpen = leftFlank

		// “A single * character can close emphasis iff
		// it is part of a right-flanking delimiter run.”

		// “A double ** can close strong emphasis iff

        given:
        label.text = "text"

        when:
        redraw()

        then:
        1 * ansi.a("text")
        0 * ansi._
    }

    def "setting styled text (emphasis only) to the label will change the style and write the text to ansi"() {
        given:
        label.text = new StyledTextOutputEvent.Span(StyledTextOutput.Style.Header, "text")

        when:
        redraw()

layout: article
---

<!--
This document is kept in the Go repo, not x/website,
because it documents the full list of known GODEBUG settings,
which are tied to a specific release.
-->

## Introduction {#intro}

Go's emphasis on backwards compatibility is one of its key strengths.
There are, however, times when we cannot maintain complete compatibility.
If code depends on buggy (including insecure) behavior,
then fixing the bug will break that code.