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- make optional semicolons explicit in grammar in all places

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except in statement list, where it is expressed in words
- allow for empty import, const, type, and var decl lists inside ()'s
- fixed grammar for inc/dec statements
- added empty statement as it appears to be accepted by 6g

R=r
DELTA=75  (23 added, 21 deleted, 31 changed)
OCL=16785
CL=16785
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Robert Griesemer 2008-10-08 17:05:30 -07:00
parent 7e241107f1
commit aed247fdb9
1 changed files with 53 additions and 51 deletions
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104
doc/go_spec.txt
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@ -4,7 +4,7 @@ The Go Programming Language Specification (DRAFT)
Robert Griesemer, Rob Pike, Ken Thompson Robert Griesemer, Rob Pike, Ken Thompson
---- ----
(October 7, 2008) (October 8, 2008)
This document is a semi-formal specification of the Go systems This document is a semi-formal specification of the Go systems
@ -97,7 +97,6 @@ Contents
Character and string literals Character and string literals
Operators and delimitors Operators and delimitors
Reserved words Reserved words
Optional semicolons
Declarations and scope rules Declarations and scope rules
Const declarations Const declarations
@ -290,7 +289,7 @@ A floating point literal represents a mathematically ideal floating point
constant of arbitrary precision, or 'ideal float'. constant of arbitrary precision, or 'ideal float'.
float_lit = float_lit =
decimals "." [ decimals ] [exponent ] | decimals "." [ decimals ] [ exponent ] |
decimals exponent | decimals exponent |
"." decimals [ exponent ] . "." decimals [ exponent ] .
decimals = decimal_digit { decimal_digit } . decimals = decimal_digit { decimal_digit } .
@ -469,25 +468,6 @@ The following words are reserved and must not be used as identifiers:
continue for import return var continue for import return var
Optional semicolons
----
Semicolons are used to terminate all declarations and statements.
The following rules apply:
1) Semicolons can be omitted after declarations at the top
(package) level.
2) Semicolons can be omitted before and after a closing
parentheses ")" or brace "}" on a list of declarations
or statements.
Semicolons that are subject to these rules are represented using
the OptSemicolon production:
OptSemicolon = [ ";" ] .
Declarations and scope rules Declarations and scope rules
---- ----
@ -497,8 +477,7 @@ function, method) and specifies properties of that entity such as its type.
Declaration = Declaration =
[ "export" ] [ "export" ]
( ConstDecl | TypeDecl | VarDecl | FunctionDecl | MethodDecl ) ( ConstDecl | TypeDecl | VarDecl | FunctionDecl | MethodDecl ) .
OptSemicolon .
Every identifier in a program must be declared; some identifiers, such as "int" Every identifier in a program must be declared; some identifiers, such as "int"
and "true", are predeclared. and "true", are predeclared.
@ -598,9 +577,9 @@ Const declarations
A constant declaration binds an identifier to the value of a constant A constant declaration binds an identifier to the value of a constant
expression (§Constant expressions). expression (§Constant expressions).
ConstDecl = "const" ( ConstSpec | "(" ConstSpecList ")" ). ConstDecl = "const" ( ConstSpec | "(" [ ConstSpecList ] ")" ) .
ConstSpec = identifier [ CompleteType ] "=" Expression . ConstSpec = identifier [ CompleteType ] "=" Expression .
ConstSpecList = ConstSpec OptSemicolon { ConstSpecOptExpr OptSemicolon }. ConstSpecList = ConstSpec { ";" ConstSpecOptExpr } [ ";" ] .
ConstSpecOptExpr = identifier [ Type ] [ "=" Expression ] . ConstSpecOptExpr = identifier [ Type ] [ "=" Expression ] .
const pi float = 3.14159265 const pi float = 3.14159265
@ -676,9 +655,9 @@ Type declarations
A type declaration specifies a new type and binds an identifier to it. A type declaration specifies a new type and binds an identifier to it.
TypeDecl = "type" ( TypeSpec | "(" TypeSpecList ")" ). TypeDecl = "type" ( TypeSpec | "(" [ TypeSpecList ] ")" ).
TypeSpec = identifier Type . TypeSpec = identifier Type .
TypeSpecList = TypeSpec OptSemicolon { TypeSpec OptSemicolon }. TypeSpecList = TypeSpec { ";" TypeSpec } [ ";" ] .
A struct or interface type may be forward-declared (§Struct types, A struct or interface type may be forward-declared (§Struct types,
§Interface types). A forward-declared type is incomplete (§Types) §Interface types). A forward-declared type is incomplete (§Types)
@ -711,9 +690,9 @@ The variable type must be a complete type (§Types).
In some forms of declaration the type of the initial value defines the type In some forms of declaration the type of the initial value defines the type
of the variable. of the variable.
VarDecl = "var" ( VarSpec | "(" VarSpecList ")" ) . VarDecl = "var" ( VarSpec | "(" [ VarSpecList ] ")" ) .
VarSpec = IdentifierList ( CompleteType [ "=" ExpressionList ] | "=" ExpressionList ) . VarSpec = IdentifierList ( CompleteType [ "=" ExpressionList ] | "=" ExpressionList ) .
VarSpecList = VarSpec OptSemicolon { VarSpec OptSemicolon } . VarSpecList = VarSpec { ";" VarSpec } [ ";" ] .
IdentifierList = identifier { "," identifier } . IdentifierList = identifier { "," identifier } .
ExpressionList = Expression { "," Expression } . ExpressionList = Expression { "," Expression } .
@ -1069,8 +1048,8 @@ an identifier and type for each field. Within a struct type no field
identifier may be declared twice and all field types must be complete identifier may be declared twice and all field types must be complete
types (§Types). types (§Types).
StructType = "struct" [ "{" [ FieldList [ ";" ] ] "}" ] . StructType = "struct" [ "{" [ FieldList ] "}" ] .
FieldList = FieldDecl { ";" FieldDecl } . FieldList = FieldDecl { ";" FieldDecl } [ ";" ] .
FieldDecl = IdentifierList CompleteType | TypeName . FieldDecl = IdentifierList CompleteType | TypeName .
// An empty struct. // An empty struct.
@ -1263,8 +1242,8 @@ Type interfaces may be specified explicitly by interface types.
An interface type denotes the set of all types that implement at least An interface type denotes the set of all types that implement at least
the set of methods specified by the interface type, and the value "nil". the set of methods specified by the interface type, and the value "nil".
InterfaceType = "interface" [ "{" [ MethodList [ ";" ] ] "}" ] . InterfaceType = "interface" [ "{" [ MethodList ] "}" ] .
MethodList = MethodSpec { ";" MethodSpec } . MethodList = MethodSpec { ";" MethodSpec } [ ";" ] .
MethodSpec = identifier FunctionType . MethodSpec = identifier FunctionType .
// A basic file interface. // A basic file interface.
@ -1928,21 +1907,22 @@ Statements
Statements control execution. Statements control execution.
Statement = Statement =
( SimpleStat | GoStat | ReturnStat | BreakStat | ContinueStat | GotoStat | Declaration | LabelDecl | EmptyStat |
Block | IfStat | SwitchStat | SelectStat | ForStat | RangeStat ) SimpleStat | GoStat | ReturnStat | BreakStat | ContinueStat | GotoStat |
OptSemicolon . FallthroughStat | Block | IfStat | SwitchStat | SelectStat | ForStat |
RangeStat .
SimpleStat = SimpleStat =
ExpressionStat | IncDecStat | Assignment | SimpleVarDecl . ExpressionStat | IncDecStat | Assignment | SimpleVarDecl .
DeclOrStat = Statements in a statement list are separated by semicolons, which can be
Declaration | LabelDecl | Statement . omitted in some cases as expressed by the OptSemicolon production.
They are optional immediately after a closing parenthesis ")" terminating a
list of declarations, or a closing brace terminating a type declaration or
a block. Specifically, they cannot be omitted after the closing brace of a
composite literal.
StatementList = DeclOrStat { DeclOrStat } . StatementList = Statement { OptSemicolon Statement } [ ";" ] .
Note that for the purpose of optional semicolons, a label declaration is neither
a declaration nor a statement. Specifically, no semicolon is allowed immediately
after a label declaration.
Label declarations Label declarations
@ -1951,6 +1931,14 @@ Label declarations
TODO write this section TODO write this section
Empty statements
----
The empty statement does nothing.
EmptyStat = .
Expression statements Expression statements
---- ----
@ -1958,6 +1946,8 @@ Expression statements
f(x+y) f(x+y)
TODO: specify restrictions. 6g only appears to allow calls here.
IncDec statements IncDec statements
---- ----
@ -1965,7 +1955,7 @@ IncDec statements
The "++" and "--" statements increment or decrement their operands The "++" and "--" statements increment or decrement their operands
by the (ideal) constant value 1. by the (ideal) constant value 1.
IncDecStat = Expression ( "++" | "--" ) . IncDecStat = PrimaryExpr ( "++" | "--" ) .
The following assignment statements (§Assignments) are semantically The following assignment statements (§Assignments) are semantically
equivalent: equivalent:
@ -2086,12 +2076,13 @@ Switch statements
Switches provide multi-way execution. Switches provide multi-way execution.
SwitchStat = "switch" [ [ Simplestat ] ";" ] [ Expression ] "{" { CaseClause } "}" . SwitchStat = "switch" [ [ Simplestat ] ";" ] [ Expression ] "{" { CaseClause } "}" .
CaseClause = Case [ StatementList ] [ "fallthrough" OptSemicolon ] . CaseClause = Case [ StatementList ] .
Case = ( "case" ExpressionList | "default" ) ":" . Case = ( "case" ExpressionList | "default" ) ":" .
There can be at most one default case in a switch statement. There can be at most one default case in a switch statement. In a case clause,
The reserved word "fallthrough" indicates that the control should flow from the last statement only may be a fallthrough statement ($Fallthrough statement).
the end of this case clause to the first statement of the next clause. It indicates that the control should flow from the end of this case clause to
the first statement of the next clause.
Each case clause effectively acts as a block for scoping purposes Each case clause effectively acts as a block for scoping purposes
($Declarations and scope rules). ($Declarations and scope rules).
@ -2389,6 +2380,17 @@ instance, this example:
is erroneous because the jump to label L skips the creation of v. is erroneous because the jump to label L skips the creation of v.
Fallthrough statements
----
A fallthrough statement transfers control to the first statement of the
next case clause in a switch statement (§Switch statements). It may only
be used in a switch statement, and only as the last statement in a case
clause of the switch statement.
FallthroughStat = "fallthrough" .
Function declarations Function declarations
---- ----
@ -2564,7 +2566,7 @@ Packages
A package is a package clause, optionally followed by import declarations, A package is a package clause, optionally followed by import declarations,
followed by a series of declarations. followed by a series of declarations.
Package = PackageClause { ImportDecl OptSemicolon } { Declaration } . Package = PackageClause { ImportDecl [ ";" ] } { Declaration [ ";" ] } .
The source text following the package clause acts like a block for scoping The source text following the package clause acts like a block for scoping
purposes ($Declarations and scope rules). purposes ($Declarations and scope rules).
@ -2582,7 +2584,7 @@ through an import declaration:
ImportDecl = "import" ( ImportSpec | "(" ImportSpecList ")" ) . ImportDecl = "import" ( ImportSpec | "(" ImportSpecList ")" ) .
ImportSpec = [ "." | PackageName ] PackageFileName . ImportSpec = [ "." | PackageName ] PackageFileName .
ImportSpecList = ImportSpec OptSemicolon { ImportSpec OptSemicolon } . ImportSpecList = ImportSpec { ";" ImportSpec } [ ";" ] .
An import statement makes the exported contents of the named An import statement makes the exported contents of the named
package file accessible in this package. package file accessible in this package.