Imported Upstream version 1.4upstream/1.4

1 files changed, 505 insertions, 394 deletions

diff --git a/doc/go_spec.html b/doc/go_spec.html
index 660c8535e..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 May 28, 2014",
+	"Subtitle": "Version of November 11, 2014",
 	"Path": "/ref/spec"
 }-->
 
@@ -479,7 +479,7 @@ Interpreted string literals are character sequences between double
 quotes <code>&quot;&quot;</code>. The text between the quotes,
 which may not contain newlines, forms the
 value of the literal, with backslash escapes interpreted as they
-are in rune literals (except that <code>\'</code> is illegal and
+are in <a href="#Rune_literals">rune literals</a> (except that <code>\'</code> is illegal and
 <code>\"</code> is legal), with the same restrictions.
 The three-digit octal (<code>\</code><i>nnn</i>)
 and two-digit hexadecimal (<code>\x</code><i>nn</i>) escapes represent individual
@@ -577,7 +577,7 @@ Numeric constants represent values of arbitrary precision and do not overflow.
 </p>
 
 <p>
-Constants may be <a href="#Types">typed</a> or untyped.
+Constants may be <a href="#Types">typed</a> or <i>untyped</i>.
 Literal constants, <code>true</code>, <code>false</code>, <code>iota</code>,
 and certain <a href="#Constant_expressions">constant expressions</a>
 containing only untyped constant operands are untyped.
@@ -598,6 +598,17 @@ not <code>int32</code> or <code>string</code>.
 </p>
 
 <p>
+An untyped constant has a <i>default type</i> which is the type to which the
+constant is implicitly converted in contexts where a typed value is required,
+for instance, in a <a href="#Short_variable_declarations">short variable declaration</a>
+such as <code>i := 0</code> where there is no explicit type.
+The default type of an untyped constant is <code>bool</code>, <code>rune</code>,
+<code>int</code>, <code>float64</code>, <code>complex128</code> or <code>string</code>
+respectively, depending on whether it is a boolean, rune, integer, floating-point,
+complex, or string constant.
+</p>
+
+<p>
 There are no constants denoting the IEEE-754 infinity and not-a-number values,
 but the <a href="/pkg/math/"><code>math</code> package</a>'s
 <a href="/pkg/math/#Inf">Inf</a>,
@@ -636,6 +647,65 @@ of evaluating <a href="#Constant_expressions">constant
 expressions</a>.
 </p>
 
+<h2 id="Variables">Variables</h2>
+
+<p>
+A variable is a storage location for holding a <i>value</i>.
+The set of permissible values is determined by the
+variable's <i><a href="#Types">type</a></i>.
+</p>
+
+<p>
+A <a href="#Variable_declarations">variable declaration</a>
+or, for function parameters and results, the signature
+of a <a href="#Function_declarations">function declaration</a>
+or <a href="#Function_literals">function literal</a> reserves
+storage for a named variable.
+
+Calling the built-in function <a href="#Allocation"><code>new</code></a>
+or taking the address of a <a href="#Composite_literals">composite literal</a>
+allocates storage for a variable at run time.
+Such an anonymous variable is referred to via a (possibly implicit)
+<a href="#Address_operators">pointer indirection</a>.
+</p>
+
+<p>
+<i>Structured</i> variables of <a href="#Array_types">array</a>, <a href="#Slice_types">slice</a>,
+and <a href="#Struct_types">struct</a> types have elements and fields that may
+be <a href="#Address_operators">addressed</a> individually. Each such element
+acts like a variable.
+</p>
+
+<p>
+The <i>static type</i> (or just <i>type</i>) of a variable is the	
+type given in its declaration, the type provided in the
+<code>new</code> call or composite literal, or the type of
+an element of a structured variable.
+Variables of interface type also have a distinct <i>dynamic type</i>,
+which is the concrete type of the value assigned to the variable at run time
+(unless the value is the predeclared identifier <code>nil</code>,
+which has no type).
+The dynamic type may vary during execution but values stored in interface
+variables are always <a href="#Assignability">assignable</a>
+to the static type of the variable.	
+</p>	
+
+<pre>
+var x interface{}  // x is nil and has static type interface{}
+var v *T           // v has value nil, static type *T
+x = 42             // x has value 42 and dynamic type int
+x = v              // x has value (*T)(nil) and dynamic type *T
+</pre>
+
+<p>
+A variable's value is retrieved by referring to the variable in an
+<a href="#Expressions">expression</a>; it is the most recent value
+<a href="#Assignments">assigned</a> to the variable.
+If a variable has not yet been assigned a value, its value is the
+<a href="#The_zero_value">zero value</a> for its type.
+</p>
+
+
 <h2 id="Types">Types</h2>
 
 <p>
@@ -662,17 +732,6 @@ type literals.
 </p>
 
 <p>
-The <i>static type</i> (or just <i>type</i>) of a variable is the
-type defined by its declaration.  Variables of interface type
-also have a distinct <i>dynamic type</i>, which
-is the actual type of the value stored in the variable at run time.
-The dynamic type may vary during execution but is always
-<a href="#Assignability">assignable</a>
-to the static type of the interface variable.  For non-interface
-types, the dynamic type is always the static type.
-</p>
-
-<p>
 Each type <code>T</code> has an <i>underlying type</i>: If <code>T</code>
 is one of the predeclared boolean, numeric, or string types, or a type literal,
 the corresponding underlying
@@ -1027,14 +1086,14 @@ struct {
 <h3 id="Pointer_types">Pointer types</h3>
 
 <p>
-A pointer type denotes the set of all pointers to variables of a given
+A pointer type denotes the set of all pointers to <a href="#Variables">variables</a> of a given
 type, called the <i>base type</i> of the pointer.
 The value of an uninitialized pointer is <code>nil</code>.
 </p>
 
 <pre class="ebnf">
 PointerType = "*" BaseType .
-BaseType = Type .
+BaseType    = Type .
 </pre>
 
 <pre>
@@ -1154,11 +1213,11 @@ interface{}
 <p>
 Similarly, consider this interface specification,
 which appears within a <a href="#Type_declarations">type declaration</a>
-to define an interface called <code>Lock</code>:
+to define an interface called <code>Locker</code>:
 </p>
 
 <pre>
-type Lock interface {
+type Locker interface {
 	Lock()
 	Unlock()
 }
@@ -1174,28 +1233,35 @@ func (p T) Unlock() { … }
 </pre>
 
 <p>
-they implement the <code>Lock</code> interface as well
+they implement the <code>Locker</code> interface as well
 as the <code>File</code> interface.
 </p>
+
 <p>
-An interface may use an interface type name <code>T</code>
-in place of a method specification.
-The effect, called embedding an interface,
-is equivalent to enumerating the methods of <code>T</code> explicitly
-in the interface.
+An interface <code>T</code> may use a (possibly qualified) interface type
+name <code>E</code> in place of a method specification. This is called
+<i>embedding</i> interface <code>E</code> in <code>T</code>; it adds
+all (exported and non-exported) methods of <code>E</code> to the interface
+<code>T</code>.
 </p>
 
 <pre>
-type ReadWrite interface {
+type ReadWriter interface {
 	Read(b Buffer) bool
 	Write(b Buffer) bool
 }
 
 type File interface {
-	ReadWrite  // same as enumerating the methods in ReadWrite
-	Lock       // same as enumerating the methods in Lock
+	ReadWriter  // same as adding the methods of ReadWriter
+	Locker      // same as adding the methods of Locker
 	Close()
 }
+
+type LockedFile interface {
+	Locker
+	File        // illegal: Lock, Unlock not unique
+	Lock()      // illegal: Lock not unique
+}
 </pre>
 
 <p>
@@ -1443,7 +1509,7 @@ is different from <code>[]string</code>.
 <h3 id="Assignability">Assignability</h3>
 
 <p>
-A value <code>x</code> is <i>assignable</i> to a variable of type <code>T</code>
+A value <code>x</code> is <i>assignable</i> to a <a href="#Variables">variable</a> of type <code>T</code>
 ("<code>x</code> is assignable to <code>T</code>") in any of these cases:
 </p>
 
@@ -1875,9 +1941,10 @@ func (tz TimeZone) String() string {
 <h3 id="Variable_declarations">Variable declarations</h3>
 
 <p>
-A variable declaration creates a variable, binds an identifier to it and
-gives it a type and optionally an initial value.
+A variable declaration creates one or more variables, binds corresponding
+identifiers to them, and gives each a type and an initial value.
 </p>
+
 <pre class="ebnf">
 VarDecl     = "var" ( VarSpec | "(" { VarSpec ";" } ")" ) .
 VarSpec     = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) .
@@ -1898,22 +1965,27 @@ var _, found = entries[name]  // map lookup; only interested in "found"
 
 <p>
 If a list of expressions is given, the variables are initialized
-by <a href="#Assignments">assigning</a> the expressions to the variables
-in order; all expressions must be consumed and all variables initialized from them.
+with the expressions following the rules for <a href="#Assignments">assignments</a>.
 Otherwise, each variable is initialized to its <a href="#The_zero_value">zero value</a>.
 </p>
 
 <p>
-If the type is present, each variable is given that type.
-Otherwise, the types are deduced from the assignment
-of the expression list.
+If a type is present, each variable is given that type.
+Otherwise, each variable is given the type of the corresponding
+initialization value in the assignment.
+If that value is an untyped constant, it is first
+<a href="#Conversions">converted</a> to its <a href="#Constants">default type</a>;
+if it is an untyped boolean value, it is first converted to type <code>bool</code>.
+The predeclared value <code>nil</code> cannot be used to initialize a variable
+with no explicit type.
 </p>
 
-<p>
-If the type is absent and the corresponding expression evaluates to an
-untyped <a href="#Constants">constant</a>, the type of the declared variable
-is as described in §<a href="#Assignments">Assignments</a>.
-</p>
+<pre>
+var d = math.Sin(0.5)  // d is int64
+var i = 42             // i is int
+var t, ok = x.(T)      // t is T, ok is bool
+var n = nil            // illegal
+</pre>
 
 <p>
 Implementation restriction: A compiler may make it illegal to declare a variable
@@ -2029,13 +2101,14 @@ and associates the method with the receiver's <i>base type</i>.
 
 <pre class="ebnf">
 MethodDecl   = "func" Receiver MethodName ( Function | Signature ) .
-Receiver     = "(" [ identifier ] [ "*" ] BaseTypeName ")" .
-BaseTypeName = identifier .
+Receiver     = Parameters .
 </pre>
 
 <p>
-The receiver type must be of the form <code>T</code> or <code>*T</code> where
-<code>T</code> is a type name. The type denoted by <code>T</code> is called
+The receiver is specified via an extra parameter section preceeding the method
+name. That parameter section must declare a single parameter, the receiver.
+Its type must be of the form <code>T</code> or <code>*T</code> (possibly using
+parentheses) where <code>T</code> is a type name. The type denoted by <code>T</code> is called
 the receiver <i>base type</i>; it must not be a pointer or interface type and
 it must be declared in the same package as the method.
 The method is said to be <i>bound</i> to the base type and the method name
@@ -2117,9 +2190,9 @@ operand only on the left-hand side of an <a href="#Assignments">assignment</a>.
 </p>
 
 <pre class="ebnf">
-Operand    = Literal | OperandName | MethodExpr | "(" Expression ")" .
-Literal    = BasicLit | CompositeLit | FunctionLit .
-BasicLit   = int_lit | float_lit | imaginary_lit | rune_lit | string_lit .
+Operand     = Literal | OperandName | MethodExpr | "(" Expression ")" .
+Literal     = BasicLit | CompositeLit | FunctionLit .
+BasicLit    = int_lit | float_lit | imaginary_lit | rune_lit | string_lit .
 OperandName = identifier | QualifiedIdent.
 </pre>
 
@@ -2241,7 +2314,8 @@ For array and slice literals the following rules apply:
 
 <p>
 <a href="#Address_operators">Taking the address</a> of a composite literal
-generates a pointer to a unique instance of the literal's value.
+generates a pointer to a unique <a href="#Variables">variable</a> initialized
+with the literal's value.
 </p>
 <pre>
 var pointer *Point3D = &amp;Point3D{y: 1000}
@@ -2375,12 +2449,11 @@ Primary expressions are the operands for unary and binary expressions.
 PrimaryExpr =
 	Operand |
 	Conversion |
-	BuiltinCall |
 	PrimaryExpr Selector |
 	PrimaryExpr Index |
 	PrimaryExpr Slice |
 	PrimaryExpr TypeAssertion |
-	PrimaryExpr Call .
+	PrimaryExpr Arguments .
 
 Selector       = "." identifier .
 Index          = "[" Expression "]" .
@@ -2388,8 +2461,7 @@ Slice          = "[" ( [ Expression ] ":" [ Expression ] ) |
                      ( [ Expression ] ":" Expression ":" Expression )
                  "]" .
 TypeAssertion  = "." "(" Type ")" .
-Call           = "(" [ ArgumentList [ "," ] ] ")" .
-ArgumentList   = ExpressionList [ "..." ] .
+Arguments      = "(" [ ( ExpressionList | Type [ "," ExpressionList ] ) [ "..." ] [ "," ] ] ")" .
 </pre>
 
 
@@ -2449,30 +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
@@ -2482,18 +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>
 
@@ -2502,13 +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
@@ -2516,9 +2586,13 @@ type T2 struct {
 	*T0
 }
 
-func (recv *T2) M2()
+func (*T2) M2()
+
+type Q *T2
 
-var p *T2  // with p != nil and p.T0 != nil
+var t T2     // with t.T0 != nil
+var p *T2    // with p != nil and (*p).T0 != nil
+var q Q = p
 </pre>
 
 <p>
@@ -2526,13 +2600,254 @@ 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>
+but the following is invalid:
+</p>
+
+<pre>
+q.M0()       // (*q).M0 is valid but not a field selector
+</pre>
+
+
+<h3 id="Method_expressions">Method expressions</h3>
+
+<p>
+If <code>M</code> is in the <a href="#Method_sets">method set</a> of type <code>T</code>,
+<code>T.M</code> is a function that is callable as a regular function
+with the same arguments as <code>M</code> prefixed by an additional
+argument that is the receiver of the method.
+</p>
+
+<pre class="ebnf">
+MethodExpr    = ReceiverType "." MethodName .
+ReceiverType  = TypeName | "(" "*" TypeName ")" | "(" ReceiverType ")" .
+</pre>
+
+<p>
+Consider a struct type <code>T</code> with two methods,
+<code>Mv</code>, whose receiver is of type <code>T</code>, and
+<code>Mp</code>, whose receiver is of type <code>*T</code>.
+</p>
+
+<pre>
+type T struct {
+	a int
+}
+func (tv  T) Mv(a int) int         { return 0 }  // value receiver
+func (tp *T) Mp(f float32) float32 { return 1 }  // pointer receiver
+
+var t T
+</pre>
+
+<p>
+The expression
+</p>
+
+<pre>
+T.Mv
+</pre>
+
+<p>
+yields a function equivalent to <code>Mv</code> but
+with an explicit receiver as its first argument; it has signature
+</p>
+
+<pre>
+func(tv T, a int) int
+</pre>
+
+<p>
+That function may be called normally with an explicit receiver, so
+these five invocations are equivalent:
+</p>
+
+<pre>
+t.Mv(7)
+T.Mv(t, 7)
+(T).Mv(t, 7)
+f1 := T.Mv; f1(t, 7)
+f2 := (T).Mv; f2(t, 7)
+</pre>
+
+<p>
+Similarly, the expression
+</p>
+
+<pre>
+(*T).Mp
+</pre>
+
+<p>
+yields a function value representing <code>Mp</code> with signature
+</p>
+
+<pre>
+func(tp *T, f float32) float32
+</pre>
+
+<p>
+For a method with a value receiver, one can derive a function
+with an explicit pointer receiver, so
+</p>
+
+<pre>
+(*T).Mv
+</pre>
+
+<p>
+yields a function value representing <code>Mv</code> with signature
+</p>
+
+<pre>
+func(tv *T, a int) int
+</pre>
+
+<p>
+Such a function indirects through the receiver to create a value
+to pass as the receiver to the underlying method;
+the method does not overwrite the value whose address is passed in
+the function call.
+</p>
+
+<p>
+The final case, a value-receiver function for a pointer-receiver method,
+is illegal because pointer-receiver methods are not in the method set
+of the value type.
+</p>
+
+<p>
+Function values derived from methods are called with function call syntax;
+the receiver is provided as the first argument to the call.
+That is, given <code>f := T.Mv</code>, <code>f</code> is invoked
+as <code>f(t, 7)</code> not <code>t.f(7)</code>.
+To construct a function that binds the receiver, use a
+<a href="#Function_literals">function literal</a> or
+<a href="#Method_values">method value</a>.
+</p>
+
+<p>
+It is legal to derive a function value from a method of an interface type.
+The resulting function takes an explicit receiver of that interface type.
+</p>
+
+<h3 id="Method_values">Method values</h3>
+
+<p>
+If the expression <code>x</code> has static type <code>T</code> and
+<code>M</code> is in the <a href="#Method_sets">method set</a> of type <code>T</code>,
+<code>x.M</code> is called a <i>method value</i>.
+The method value <code>x.M</code> is a function value that is callable
+with the same arguments as a method call of <code>x.M</code>.
+The expression <code>x</code> is evaluated and saved during the evaluation of the
+method value; the saved copy is then used as the receiver in any calls,
+which may be executed later.
+</p>
+
+<p>
+The type <code>T</code> may be an interface or non-interface type.
+</p>
+
+<p>
+As in the discussion of <a href="#Method_expressions">method expressions</a> above,
+consider a struct type <code>T</code> with two methods,
+<code>Mv</code>, whose receiver is of type <code>T</code>, and
+<code>Mp</code>, whose receiver is of type <code>*T</code>.
+</p>
+
+<pre>
+type T struct {
+	a int
+}
+func (tv  T) Mv(a int) int         { return 0 }  // value receiver
+func (tp *T) Mp(f float32) float32 { return 1 }  // pointer receiver
+
+var t T
+var pt *T
+func makeT() T
+</pre>
+
+<p>
+The expression
+</p>
+
+<pre>
+t.Mv
+</pre>
+
+<p>
+yields a function value of type
+</p>
+
+<pre>
+func(int) int
+</pre>
+
+<p>
+These two invocations are equivalent:
+</p>
+
+<pre>
+t.Mv(7)
+f := t.Mv; f(7)
+</pre>
+
+<p>
+Similarly, the expression
+</p>
+
+<pre>
+pt.Mp
+</pre>
+
+<p>
+yields a function value of type
+</p>
+
+<pre>
+func(float32) float32
+</pre>
+
+<p>
+As with <a href="#Selectors">selectors</a>, a reference to a non-interface method with a value receiver
+using a pointer will automatically dereference that pointer: <code>pt.Mv</code> is equivalent to <code>(*pt).Mv</code>.
+</p>
+
+<p>
+As with <a href="#Calls">method calls</a>, a reference to a non-interface method with a pointer receiver
+using an addressable value will automatically take the address of that value: <code>t.Mp</code> is equivalent to <code>(&amp;t).Mp</code>.
+</p>
+
+<pre>
+f := t.Mv; f(7)   // like t.Mv(7)
+f := pt.Mp; f(7)  // like pt.Mp(7)
+f := pt.Mv; f(7)  // like (*pt).Mv(7)
+f := t.Mp; f(7)   // like (&amp;t).Mp(7)
+f := makeT().Mp   // invalid: result of makeT() is not addressable
+</pre>
+
+<p>
+Although the examples above use non-interface types, it is also legal to create a method value
+from a value of interface type.
+</p>
 
-p.M2()  // (*p).M2()
-p.M1()  // ((*p).T1).M1()
-p.M0()  // ((*p).T0).M0()
+<pre>
+var i interface { M(int) } = myVal
+f := i.M; f(7)  // like i.M(7)
 </pre>
 
 
@@ -2625,7 +2940,7 @@ Otherwise <code>a[x]</code> is illegal.
 
 <p>
 An index expression on a map <code>a</code> of type <code>map[K]V</code>
-may be used in an assignment or initialization of the special form
+used in an <a href="#Assignments">assignment</a> or initialization of the special form
 </p>
 
 <pre>
@@ -2635,11 +2950,9 @@ var v, ok = a[x]
 </pre>
 
 <p>
-where the result of the index expression is a pair of values with types
-<code>(V, bool)</code>. In this form, the value of <code>ok</code> is
+yields an additional untyped boolean value. The value of <code>ok</code> is
 <code>true</code> if the key <code>x</code> is present in the map, and
-<code>false</code> otherwise. The value of <code>v</code> is the value
-<code>a[x]</code> as in the single-result form.
+<code>false</code> otherwise.
 </p>
 
 <p>
@@ -2824,7 +3137,7 @@ r := y.(io.Reader)     // r has type io.Reader and y must implement both I and i
 </pre>
 
 <p>
-If a type assertion is used in an <a href="#Assignments">assignment</a> or initialization of the form
+A type assertion used in an <a href="#Assignments">assignment</a> or initialization of the special form
 </p>
 
 <pre>
@@ -2834,13 +3147,10 @@ var v, ok = x.(T)
 </pre>
 
 <p>
-the result of the assertion is a pair of values with types <code>(T, bool)</code>.
-If the assertion holds, the expression returns the pair <code>(x.(T), true)</code>;
-otherwise, the expression returns <code>(Z, false)</code> where <code>Z</code>
-is the <a href="#The_zero_value">zero value</a> for type <code>T</code>.
+yields an additional untyped boolean value. The value of <code>ok</code> is <code>true</code>
+if the assertion holds. Otherwise it is <code>false</code> and the value of <code>v</code> is
+the <a href="#The_zero_value">zero value</a> for type <code>T</code>.
 No run-time panic occurs in this case.
-The type assertion in this construct thus acts like a function call
-returning a value and a boolean indicating success.
 </p>
 
 
@@ -2870,7 +3180,7 @@ the method.
 <pre>
 math.Atan2(x, y)  // function call
 var pt *Point
-pt.Scale(3.5)  // method call with receiver pt
+pt.Scale(3.5)     // method call with receiver pt
 </pre>
 
 <p>
@@ -3375,13 +3685,13 @@ or an array indexing operation of an addressable array.
 As an exception to the addressability requirement, <code>x</code> may also be a
 (possibly parenthesized)
 <a href="#Composite_literals">composite literal</a>.
-If the evaluation of <code>x</code> would cause a <a href="#Run_time_panics">run-time panic</a>, 
+If the evaluation of <code>x</code> would cause a <a href="#Run_time_panics">run-time panic</a>,
 then the evaluation of <code>&amp;x</code> does too.
 </p>
 
 <p>
 For an operand <code>x</code> of pointer type <code>*T</code>, the pointer
-indirection <code>*x</code> denotes the value of type <code>T</code> pointed
+indirection <code>*x</code> denotes the <a href="#Variables">variable</a> of type <code>T</code> pointed
 to by <code>x</code>.
 If <code>x</code> is <code>nil</code>, an attempt to evaluate <code>*x</code>
 will cause a <a href="#Run_time_panics">run-time panic</a>.
@@ -3422,7 +3732,7 @@ f(&lt;-ch)
 </pre>
 
 <p>
-A receive expression used in an assignment or initialization of the form
+A receive expression used in an <a href="#Assignments">assignment</a> or initialization of the special form
 </p>
 
 <pre>
@@ -3432,7 +3742,7 @@ var x, ok = &lt;-ch
 </pre>
 
 <p>
-yields an additional result of type <code>bool</code> reporting whether the
+yields an additional untyped boolean result reporting whether the
 communication succeeded. The value of <code>ok</code> is <code>true</code>
 if the value received was delivered by a successful send operation to the
 channel, or <code>false</code> if it is a zero value generated because the
@@ -3440,232 +3750,6 @@ channel is closed and empty.
 </p>
 
 
-<h3 id="Method_expressions">Method expressions</h3>
-
-<p>
-If <code>M</code> is in the <a href="#Method_sets">method set</a> of type <code>T</code>,
-<code>T.M</code> is a function that is callable as a regular function
-with the same arguments as <code>M</code> prefixed by an additional
-argument that is the receiver of the method.
-</p>
-
-<pre class="ebnf">
-MethodExpr    = ReceiverType "." MethodName .
-ReceiverType  = TypeName | "(" "*" TypeName ")" | "(" ReceiverType ")" .
-</pre>
-
-<p>
-Consider a struct type <code>T</code> with two methods,
-<code>Mv</code>, whose receiver is of type <code>T</code>, and
-<code>Mp</code>, whose receiver is of type <code>*T</code>.
-</p>
-
-<pre>
-type T struct {
-	a int
-}
-func (tv  T) Mv(a int) int         { return 0 }  // value receiver
-func (tp *T) Mp(f float32) float32 { return 1 }  // pointer receiver
-
-var t T
-</pre>
-
-<p>
-The expression
-</p>
-
-<pre>
-T.Mv
-</pre>
-
-<p>
-yields a function equivalent to <code>Mv</code> but
-with an explicit receiver as its first argument; it has signature
-</p>
-
-<pre>
-func(tv T, a int) int
-</pre>
-
-<p>
-That function may be called normally with an explicit receiver, so
-these five invocations are equivalent:
-</p>
-
-<pre>
-t.Mv(7)
-T.Mv(t, 7)
-(T).Mv(t, 7)
-f1 := T.Mv; f1(t, 7)
-f2 := (T).Mv; f2(t, 7)
-</pre>
-
-<p>
-Similarly, the expression
-</p>
-
-<pre>
-(*T).Mp
-</pre>
-
-<p>
-yields a function value representing <code>Mp</code> with signature
-</p>
-
-<pre>
-func(tp *T, f float32) float32
-</pre>
-
-<p>
-For a method with a value receiver, one can derive a function
-with an explicit pointer receiver, so
-</p>
-
-<pre>
-(*T).Mv
-</pre>
-
-<p>
-yields a function value representing <code>Mv</code> with signature
-</p>
-
-<pre>
-func(tv *T, a int) int
-</pre>
-
-<p>
-Such a function indirects through the receiver to create a value
-to pass as the receiver to the underlying method;
-the method does not overwrite the value whose address is passed in
-the function call.
-</p>
-
-<p>
-The final case, a value-receiver function for a pointer-receiver method,
-is illegal because pointer-receiver methods are not in the method set
-of the value type.
-</p>
-
-<p>
-Function values derived from methods are called with function call syntax;
-the receiver is provided as the first argument to the call.
-That is, given <code>f := T.Mv</code>, <code>f</code> is invoked
-as <code>f(t, 7)</code> not <code>t.f(7)</code>.
-To construct a function that binds the receiver, use a
-<a href="#Function_literals">function literal</a> or
-<a href="#Method_values">method value</a>.
-</p>
-
-<p>
-It is legal to derive a function value from a method of an interface type.
-The resulting function takes an explicit receiver of that interface type.
-</p>
-
-<h3 id="Method_values">Method values</h3>
-
-<p>
-If the expression <code>x</code> has static type <code>T</code> and
-<code>M</code> is in the <a href="#Method_sets">method set</a> of type <code>T</code>,
-<code>x.M</code> is called a <i>method value</i>.
-The method value <code>x.M</code> is a function value that is callable
-with the same arguments as a method call of <code>x.M</code>.
-The expression <code>x</code> is evaluated and saved during the evaluation of the
-method value; the saved copy is then used as the receiver in any calls,
-which may be executed later.
-</p>
-
-<p>
-The type <code>T</code> may be an interface or non-interface type.
-</p>
-
-<p>
-As in the discussion of <a href="#Method_expressions">method expressions</a> above,
-consider a struct type <code>T</code> with two methods,
-<code>Mv</code>, whose receiver is of type <code>T</code>, and
-<code>Mp</code>, whose receiver is of type <code>*T</code>.
-</p>
-
-<pre>
-type T struct {
-	a int
-}
-func (tv  T) Mv(a int) int         { return 0 }  // value receiver
-func (tp *T) Mp(f float32) float32 { return 1 }  // pointer receiver
-
-var t T
-var pt *T
-func makeT() T
-</pre>
-
-<p>
-The expression
-</p>
-
-<pre>
-t.Mv
-</pre>
-
-<p>
-yields a function value of type
-</p>
-
-<pre>
-func(int) int
-</pre>
-
-<p>
-These two invocations are equivalent:
-</p>
-
-<pre>
-t.Mv(7)
-f := t.Mv; f(7)
-</pre>
-
-<p>
-Similarly, the expression
-</p>
-
-<pre>
-pt.Mp
-</pre>
-
-<p>
-yields a function value of type
-</p>
-
-<pre>
-func(float32) float32
-</pre>
-
-<p>
-As with <a href="#Selectors">selectors</a>, a reference to a non-interface method with a value receiver
-using a pointer will automatically dereference that pointer: <code>pt.Mv</code> is equivalent to <code>(*pt).Mv</code>.
-</p>
-
-<p>
-As with <a href="#Calls">method calls</a>, a reference to a non-interface method with a pointer receiver
-using an addressable value will automatically take the address of that value: <code>t.Mp</code> is equivalent to <code>(&amp;t).Mp</code>.
-</p>
-
-<pre>
-f := t.Mv; f(7)   // like t.Mv(7)
-f := pt.Mp; f(7)  // like pt.Mp(7)
-f := pt.Mv; f(7)  // like (*pt).Mv(7)
-f := t.Mp; f(7)   // like (&amp;t).Mp(7)
-f := makeT().Mp   // invalid: result of makeT() is not addressable
-</pre>
-
-<p>
-Although the examples above use non-interface types, it is also legal to create a method value
-from a value of interface type.
-</p>
-
-<pre>
-var i interface { M(int) } = myVal
-f := i.M; f(7)  // like i.M(7)
-</pre>
-
 <h3 id="Conversions">Conversions</h3>
 
 <p>
@@ -4055,7 +4139,7 @@ n := map[int]int{a: f()}      // n may be {2: 3} or {3: 3}: evaluation order bet
 <p>
 At package level, initialization dependencies override the left-to-right rule
 for individual initialization expressions, but not for operands within each
-expression: 
+expression:
 </p>
 
 <pre>
@@ -4314,7 +4398,7 @@ a[i] = 23
 
 <p>
 An <i>assignment operation</i> <code>x</code> <i>op</i><code>=</code>
-<code>y</code> where <i>op</i> is a binary arithmetic operation equivalent
+<code>y</code> where <i>op</i> is a binary arithmetic operation is equivalent
 to <code>x</code> <code>=</code> <code>x</code> <i>op</i>
 <code>y</code> but evaluates <code>x</code>
 only once.  The <i>op</i><code>=</code> construct is a single token.
@@ -4332,8 +4416,8 @@ i &amp;^= 1&lt;&lt;n
 A tuple assignment assigns the individual elements of a multi-valued
 operation to a list of variables.  There are two forms.  In the
 first, the right hand operand is a single multi-valued expression
-such as a function evaluation or <a href="#Channel_types">channel</a> or
-<a href="#Map_types">map</a> operation or a <a href="#Type_assertions">type assertion</a>.
+such as a function call, a <a href="#Channel_types">channel</a> or
+<a href="#Map_types">map</a> operation, or a <a href="#Type_assertions">type assertion</a>.
 The number of operands on the left
 hand side must match the number of values.  For instance, if
 <code>f</code> is a function returning two values,
@@ -4407,23 +4491,21 @@ to the type of the operand to which it is assigned, with the following special c
 </p>
 
 <ol>
-<li><p>
-	If an untyped <a href="#Constants">constant</a>
+<li>
+	Any typed value may be assigned to the blank identifier.
+</li>
+
+<li>
+	If an untyped constant
 	is assigned to a variable of interface type or the blank identifier,
-	the constant is first <a href="#Conversions">converted</a> to type
-	<code>bool</code>, <code>rune</code>, <code>int</code>, <code>float64</code>,
-	<code>complex128</code> or <code>string</code> respectively, depending on
-	whether the value is a boolean, rune, integer, floating-point, complex, or
-	string constant.
-</p></li>
-
-<li><p>
-	<!-- Note that the result of a comparison is an untyped bool that may not be constant. -->
-	If a left-hand side is the blank identifier, any typed or non-constant
-	value except for the predeclared identifier
-	<a href="#Predeclared_identifiers"><code>nil</code></a>
-	may be assigned to it.
-</p></li>
+	the constant is first <a href="#Conversions">converted</a> to its
+	 <a href="#Constants">default type</a>.
+</li>
+
+<li>
+	If an untyped boolean value is assigned to a variable of interface type or
+	the blank identifier, it is first converted to type <code>bool</code>.
+</li>
 </ol>
 
 <h3 id="If_statements">If statements</h3>
@@ -4678,6 +4760,7 @@ additionally it may specify an <i>init</i>
 and a <i>post</i> statement, such as an assignment,
 an increment or decrement statement. The init statement may be a
 <a href="#Short_variable_declarations">short variable declaration</a>, but the post statement must not.
+Variables declared by the init statement are re-used in each iteration.
 </p>
 
 <pre class="ebnf">
@@ -4713,41 +4796,42 @@ for      { S() }    is the same as    for true     { S() }
 A "for" statement with a "range" clause
 iterates through all entries of an array, slice, string or map,
 or values received on a channel. For each entry it assigns <i>iteration values</i>
-to corresponding <i>iteration variables</i> and then executes the block.
+to corresponding <i>iteration variables</i> if present and then executes the block.
 </p>
 
 <pre class="ebnf">
-RangeClause = ( ExpressionList "=" | IdentifierList ":=" ) "range" Expression .
+RangeClause = [ ExpressionList "=" | IdentifierList ":=" ] "range" Expression .
 </pre>
 
 <p>
 The expression on the right in the "range" clause is called the <i>range expression</i>,
 which may be an array, pointer to an array, slice, string, map, or channel permitting
 <a href="#Receive_operator">receive operations</a>.
-As with an assignment, the operands on the left must be
+As with an assignment, if present the operands on the left must be
 <a href="#Address_operators">addressable</a> or map index expressions; they
-denote the iteration variables. If the range expression is a channel, only
-one iteration variable is permitted, otherwise there may be one or two. In the latter case,
-if the second iteration variable is the <a href="#Blank_identifier">blank identifier</a>,
-the range clause is equivalent to the same clause with only the first variable present.
+denote the iteration variables. If the range expression is a channel, at most
+one iteration variable is permitted, otherwise there may be up to two.
+If the last iteration variable is the <a href="#Blank_identifier">blank identifier</a>,
+the range clause is equivalent to the same clause without that identifier.
 </p>
 
 <p>
 The range expression is evaluated once before beginning the loop,
-with one exception. If the range expression is an array or a pointer to an array
-and only the first iteration value is present, only the range expression's
-length is evaluated; if that length is constant
-<a href="#Length_and_capacity">by definition</a>,
+with one exception: if the range expression is an array or a pointer to an array
+and at most one iteration variable is present, only the range expression's
+length is evaluated; if that length is constant,
+<a href="#Length_and_capacity">by definition</a>
 the range expression itself will not be evaluated.
 </p>
 
 <p>
 Function calls on the left are evaluated once per iteration.
-For each iteration, iteration values are produced as follows:
+For each iteration, iteration values are produced as follows
+if the respective iteration variables are present:
 </p>
 
 <pre class="grammar">
-Range expression                          1st value          2nd value (if 2nd variable is present)
+Range expression                          1st value          2nd value
 
 array or slice  a  [n]E, *[n]E, or []E    index    i  int    a[i]       E
 string          s  string type            index    i  int    see below  rune
@@ -4759,7 +4843,7 @@ channel         c  chan E, &lt;-chan E       element  e  E
 <li>
 For an array, pointer to array, or slice value <code>a</code>, the index iteration
 values are produced in increasing order, starting at element index 0.
-If only the first iteration variable is present, the range loop produces
+If at most one iteration variable is present, the range loop produces
 iteration values from 0 up to <code>len(a)-1</code> and does not index into the array
 or slice itself. For a <code>nil</code> slice, the number of iterations is 0.
 </li>
@@ -4803,7 +4887,7 @@ The iteration variables may be declared by the "range" clause using a form of
 <a href="#Short_variable_declarations">short variable declaration</a>
 (<code>:=</code>).
 In this case their types are set to the types of the respective iteration values
-and their <a href="#Declarations_and_scope">scope</a> ends at the end of the "for"
+and their <a href="#Declarations_and_scope">scope</a> is the block of the "for"
 statement; they are re-used in each iteration.
 If the iteration variables are declared outside the "for" statement,
 after execution their values will be those of the last iteration.
@@ -4840,6 +4924,9 @@ var ch chan Work = producer()
 for w := range ch {
 	doWork(w)
 }
+
+// empty a channel
+for range ch {}
 </pre>
 
 
@@ -5242,13 +5329,16 @@ Calls of built-in functions are restricted as for
 </p>
 
 <p>
-Each time the "defer" statement
+Each time a "defer" statement
 executes, the function value and parameters to the call are
 <a href="#Calls">evaluated as usual</a>
-and saved anew but the actual function body is not executed.
-Instead, deferred functions are executed immediately before
+and saved anew but the actual function is not invoked.
+Instead, deferred functions are invoked immediately before
 the surrounding function returns, in the reverse order
 they were deferred.
+If a deferred function value evaluates
+to <code>nil</code>, execution <a href="#Handling_panics">panics</a>
+when the function is invoked, not when the "defer" statement is executed.
 </p>
 
 <p>
@@ -5295,11 +5385,6 @@ so they can only appear in <a href="#Calls">call expressions</a>;
 they cannot be used as function values.
 </p>
 
-<pre class="ebnf">
-BuiltinCall = identifier "(" [ BuiltinArgs [ "," ] ] ")" .
-BuiltinArgs = Type [ "," ArgumentList ] | ArgumentList .
-</pre>
-
 <h3 id="Close">Close</h3>
 
 <p>
@@ -5378,9 +5463,11 @@ var z complex128
 <h3 id="Allocation">Allocation</h3>
 
 <p>
-The built-in function <code>new</code> takes a type <code>T</code> and
-returns a value of type <code>*T</code>.
-The memory is initialized as described in the section on
+The built-in function <code>new</code> takes a type <code>T</code>,
+allocates storage for a <a href="#Variables">variable</a> of that type
+at run time, and returns a value of type <code>*T</code>
+<a href="#Pointer_types">pointing</a> to it.
+The variable is initialized as described in the section on
 <a href="#The_zero_value">initial values</a>.
 </p>
 
@@ -5398,10 +5485,10 @@ new(S)
 </pre>
 
 <p>
-dynamically allocates memory for a variable of type <code>S</code>,
+allocates storage for a variable of type <code>S</code>,
 initializes it (<code>a=0</code>, <code>b=0.0</code>),
 and returns a value of type <code>*S</code> containing the address
-of the memory.
+of the location.
 </p>
 
 <h3 id="Making_slices_maps_and_channels">Making slices, maps and channels</h3>
@@ -5868,10 +5955,12 @@ func main() {
 
 <h3 id="The_zero_value">The zero value</h3>
 <p>
-When memory is allocated to store a value, either through a declaration
-or a call of <code>make</code> or <code>new</code>,
-and no explicit initialization is provided, the memory is
-given a default initialization.  Each element of such a value is
+When storage is allocated for a <a href="#Variables">variable</a>,
+either through a declaration or a call of <code>new</code>, or when
+a new value is created, either through a composite literal or a call
+of <code>make</code>,
+and no explicit initialization is provided, the variable or value is
+given a default value.  Each element of such a variable or value is
 set to the <i>zero value</i> for its type: <code>false</code> for booleans,
 <code>0</code> for integers, <code>0.0</code> for floats, <code>""</code>
 for strings, and <code>nil</code> for pointers, functions, interfaces, slices, channels, and maps.
@@ -5915,20 +6004,42 @@ var t T
 </pre>
 
 <h3 id="Package_initialization">Package initialization</h3>
+
 <p>
-Within a package, package-level variables are initialized according
-to their <i>dependencies</i>: if a variable <code>x</code> depends on
-a variable <code>y</code>, <code>x</code> will be initialized after
-<code>y</code>.
+Within a package, package-level variables are initialized in
+<i>declaration order</i> but after any of the variables
+they <i>depend</i> on.
+</p>
+
+<p>
+More precisely, a package-level variable is considered <i>ready for
+initialization</i> if it is not yet initialized and either has
+no <a href="#Variable_declarations">initialization expression</a> or
+its initialization expression has no dependencies on uninitialized variables.
+Initialization proceeds by repeatedly initializing the next package-level
+variable that is earliest in declaration order and ready for initialization,
+until there are no variables ready for initialization.
+</p>
+
+<p>
+If any variables are still uninitialized when this
+process ends, those variables are part of one or more initialization cycles,
+and the program is not valid.
+</p>
+
+<p>
+The declaration order of variables declared in multiple files is determined
+by the order in which the files are presented to the compiler: Variables
+declared in the first file are declared before any of the variables declared
+in the second file, and so on.
 </p>
 
 <p>
 Dependency analysis does not rely on the actual values of the
 variables, only on lexical <i>references</i> to them in the source,
-analyzed transitively. For instance, a variable <code>x</code>'s
-<a href="#Variable_declarations">initialization expression</a>
-may refer to a function whose body refers to variable <code>y</code>;
-if so, <code>x</code> depends on <code>y</code>.
+analyzed transitively. For instance, if a variable <code>x</code>'s
+initialization expression refers to a function whose body refers to
+variable <code>y</code> then <code>x</code> depends on <code>y</code>.
 Specifically:
 </p>
 
@@ -5941,7 +6052,7 @@ variable or function.
 <li>
 A reference to a method <code>m</code> is a
 <a href="#Method_values">method value</a> or
-<a href="#Method_expressions">method expression</a> of the form 
+<a href="#Method_expressions">method expression</a> of the form
 <code>t.m</code>, where the (static) type of <code>t</code> is
 not an interface type, and the method <code>m</code> is in the
 <a href="#Method_sets">method set</a> of <code>t</code>.
@@ -5950,7 +6061,7 @@ It is immaterial whether the resulting function value
 </li>
 
 <li>
-A variable, function, or method <code>x</code> depends on a variable 
+A variable, function, or method <code>x</code> depends on a variable
 <code>y</code> if <code>x</code>'s initialization expression or body
 (for functions and methods) contains a reference to <code>y</code>
 or to a function or method that depends on <code>y</code>.
@@ -5961,11 +6072,6 @@ or to a function or method that depends on <code>y</code>.
 Dependency analysis is performed per package; only references referring
 to variables, functions, and methods declared in the current package
 are considered.
-It is an error if variable dependencies form a cycle
-(but dependency cycles containing no variables are permitted).
-If two variables are independent of each other,
-they are initialized in the order they are declared
-in the source, possibly in multiple files, as presented to the compiler.
 </p>
 
 <p>
@@ -5988,8 +6094,6 @@ func f() int {
 
 <p>
 the initialization order is <code>d</code>, <code>b</code>, <code>c</code>, <code>a</code>.
-Since <code>b</code> and <code>c</code> are independent of each other, they are
-initialized in declaration order (<code>b</code> before <code>c</code>).
 </p>
 
 <p>
@@ -6002,7 +6106,7 @@ func init() { … }
 </pre>
 
 <p>
-Multiple such functions may be defined, even within a single 
+Multiple such functions may be defined, even within a single
 source file. The <code>init</code> identifier is not
 <a href="#Declarations_and_scope">declared</a> and thus
 <code>init</code> functions cannot be referred to from anywhere
@@ -6032,6 +6136,12 @@ the <code>init</code> functions: it will not invoke the next one
 until the previous one has returned.
 </p>
 
+<p>
+To ensure reproducible initialization behavior, build systems are encouraged
+to present multiple files belonging to the same package in lexical file name
+order to a compiler.
+</p>
+
 
 <h3 id="Program_execution">Program execution</h3>
 <p>
@@ -6106,8 +6216,8 @@ type Error interface {
 The built-in package <code>unsafe</code>, known to the compiler,
 provides facilities for low-level programming including operations
 that violate the type system. A package using <code>unsafe</code>
-must be vetted manually for type safety.  The package provides the
-following interface:
+must be vetted manually for type safety and may not be portable.
+The package provides the following interface:
 </p>
 
 <pre class="grammar">
@@ -6122,10 +6232,11 @@ func Sizeof(variable ArbitraryType) uintptr
 </pre>
 
 <p>
-Any pointer or value of <a href="#Types">underlying type</a> <code>uintptr</code> can be converted to
-a <code>Pointer</code> type and vice versa.
 A <code>Pointer</code> is a <a href="#Pointer_types">pointer type</a> but a <code>Pointer</code>
 value may not be <a href="#Address_operators">dereferenced</a>.
+Any pointer or value of <a href="#Types">underlying type</a> <code>uintptr</code> can be converted to
+a <code>Pointer</code> type and vice versa.
+The effect of converting between <code>Pointer</code> and <code>uintptr</code> is implementation-defined.
 </p>
 
 <pre>