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