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| -rw-r--r-- | doc/go_spec.html | 68 |
1 files changed, 42 insertions, 26 deletions
diff --git a/doc/go_spec.html b/doc/go_spec.html index 050c06465..ca0deb56a 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -1,6 +1,6 @@ <!--{ "Title": "The Go Programming Language Specification", - "Subtitle": "Version of October 27, 2014", + "Subtitle": "Version of November 11, 2014", "Path": "/ref/spec" }--> @@ -2521,30 +2521,40 @@ The following rules apply to selectors: <ol> <li> For a value <code>x</code> of type <code>T</code> or <code>*T</code> -where <code>T</code> is not an interface type, +where <code>T</code> is not a pointer or interface type, <code>x.f</code> denotes the field or method at the shallowest depth in <code>T</code> where there is such an <code>f</code>. If there is not exactly <a href="#Uniqueness_of_identifiers">one <code>f</code></a> with shallowest depth, the selector expression is illegal. </li> + <li> -For a variable <code>x</code> of type <code>I</code> where <code>I</code> +For a value <code>x</code> of type <code>I</code> where <code>I</code> is an interface type, <code>x.f</code> denotes the actual method with name -<code>f</code> of the value assigned to <code>x</code>. +<code>f</code> of the dynamic value of <code>x</code>. If there is no method with name <code>f</code> in the <a href="#Method_sets">method set</a> of <code>I</code>, the selector expression is illegal. </li> + +<li> +As an exception, if the type of <code>x</code> is a named pointer type +and <code>(*x).f</code> is a valid selector expression denoting a field +(but not a method), <code>x.f</code> is shorthand for <code>(*x).f</code>. +</li> + <li> In all other cases, <code>x.f</code> is illegal. </li> + <li> If <code>x</code> is of pointer type and has the value <code>nil</code> and <code>x.f</code> denotes a struct field, assigning to or evaluating <code>x.f</code> causes a <a href="#Run_time_panics">run-time panic</a>. </li> + <li> If <code>x</code> is of interface type and has the value <code>nil</code>, <a href="#Calls">calling</a> or @@ -2554,18 +2564,6 @@ causes a <a href="#Run_time_panics">run-time panic</a>. </ol> <p> -Selectors automatically <a href="#Address_operators">dereference</a> -pointers to structs. -If <code>x</code> is a pointer to a struct, <code>x.y</code> -is shorthand for <code>(*x).y</code>; if the field <code>y</code> -is also a pointer to a struct, <code>x.y.z</code> is shorthand -for <code>(*(*x).y).z</code>, and so on. -If <code>x</code> contains an anonymous field of type <code>*A</code>, -where <code>A</code> is also a struct type, -<code>x.f</code> is shorthand for <code>(*x.A).f</code>. -</p> - -<p> For example, given the declarations: </p> @@ -2574,13 +2572,13 @@ type T0 struct { x int } -func (recv *T0) M0() +func (*T0) M0() type T1 struct { y int } -func (recv T1) M1() +func (T1) M1() type T2 struct { z int @@ -2588,9 +2586,13 @@ type T2 struct { *T0 } -func (recv *T2) M2() +func (*T2) M2() -var p *T2 // with p != nil and p.T0 != nil +type Q *T2 + +var t T2 // with t.T0 != nil +var p *T2 // with p != nil and (*p).T0 != nil +var q Q = p </pre> <p> @@ -2598,13 +2600,27 @@ one may write: </p> <pre> -p.z // (*p).z -p.y // ((*p).T1).y -p.x // (*(*p).T0).x +t.z // t.z +t.y // t.T1.y +t.x // (*t.TO).x + +p.z // (*p).z +p.y // (*p).T1.y +p.x // (*(*p).T0).x + +q.x // (*(*q).T0).x (*q).x is a valid field selector + +p.M2() // p.M2() M2 expects *T2 receiver +p.M1() // ((*p).T1).M1() M1 expects T1 receiver +p.M0() // ((&(*p).T0)).M0() M0 expects *T0 receiver, see section on Calls +</pre> -p.M2() // (*p).M2() -p.M1() // ((*p).T1).M1() -p.M0() // ((*p).T0).M0() +<p> +but the following is invalid: +</p> + +<pre> +q.M0() // (*q).M0 is valid but not a field selector </pre> |