for _, id := range spec.Names {
								mark(id)
							}
						case *ast.TypeSpec:
							mark(spec.Name)
						}
					}
				}
				return true // look at specs
			case *ast.FuncDecl:
				if isDeprecated(n.Doc) {
					mark(n.Name)
				}
				return false
			case *ast.TypeSpec:
				if isDeprecated(n.Doc) {
					mark(n.Name)
				}

Type declarations come in two forms: alias declarations and type definitions.
</p>

<pre class="ebnf">
TypeDecl = "type" ( TypeSpec | "(" { TypeSpec ";" } ")" ) .
TypeSpec = AliasDecl | TypeDef .
</pre>

<h4 id="Alias_declarations">Alias declarations</h4>

<p>
An alias declaration binds an identifier to the given type
[<a href="#Go_1.9">Go 1.9</a>].

	case *ast.ValueSpec:
		f.walk(&n.Type, ctxType, visit)
		if len(n.Names) == 2 && len(n.Values) == 1 {
			f.walk(&n.Values[0], ctxAssign2, visit)
		} else {
			f.walk(n.Values, ctxExpr, visit)
		}
	case *ast.TypeSpec:
		if n.TypeParams != nil {
			f.walk(n.TypeParams, ctxParam, visit)
		}
		f.walk(&n.Type, ctxType, visit)

	case *ast.BadDecl:
	case *ast.GenDecl:
		f.walk(n.Specs, ctxSpec, visit)

        regarding when retracing needs to occur by implementing the Tracing
        Protocol available through
        `tf.types.experimental.SupportsTracingProtocol`.
    *   `TypeSpec` classes (as associated with `ExtensionTypes`) also implement
        the Tracing Protocol which can be overridden if necessary.
    *   The newly introduced `reduce_retracing` option also uses the Tracing