From 9905cec0dc04fd7cddb7c7504006b7aa618abd94 Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Mon, 4 Mar 2013 13:55:35 -0800 Subject: [PATCH] spec: terminating statements for functions The only functional change is the new section on terminating statements. There is a minor syntax rewrite (not change) of function declarations to make it easier to refer to the notion of a function from all places where it is used (function decls, method decls, and function literals). Includes some minor fixes/additions of missing links. Based closely on Russ' proposal. Fixes #65. R=rsc, r, iant, ken, bradfitz CC=golang-dev https://golang.org/cl/7415050 --- doc/go_spec.html | 122 ++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 105 insertions(+), 17 deletions(-) diff --git a/doc/go_spec.html b/doc/go_spec.html index 83e0f582de..0fc918471d 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -1469,12 +1469,13 @@ Any value may be assigned to the blank identifierBlocks

-A block is a sequence of declarations and statements within matching -brace brackets. +A block is a possibly empty sequence of declarations and statements +within matching brace brackets. 

-Block = "{" { Statement ";" } "}" .
+Block = "{" StatementList "}" .
+StatementList = { Statement ";" } .

@@ -1490,10 +1491,13 @@ In addition to explicit blocks in the source code, there are implicit blocks:

  • Each file has a file block containing all Go source text in that file.
    • -
  • Each if, for, and switch +
  • Each "if", + "for", and + "switch" statement is considered to be in its own implicit block.
    • -
  • Each clause in a switch or select statement +
  • Each clause in a "switch" + or "select" statement acts as an implicit block.
    • @@ -1948,11 +1952,18 @@ to a function. 

    -FunctionDecl = "func" FunctionName Signature [ Body ] .
+FunctionDecl = "func" FunctionName ( Function | Signature ) .
 FunctionName = identifier .
-Body         = Block .
+Function     = Signature FunctionBody .
+FunctionBody = Block .
    +

    +If the function's signature declares +result parameters, the function body's statement list must end in +a terminating statement. +

    +

    A function declaration may omit the body. Such a declaration provides the signature for a function implemented outside Go, such as an assembly routine. @@ -1972,13 +1983,13 @@ func flushICache(begin, end uintptr) // implemented externally

    Method declarations

    -A method is a function with a receiver. -A method declaration binds an identifier, the method name, to a method. -It also associates the method with the receiver's base type. +A method is a function with a receiver. +A method declaration binds an identifier, the method name, to a method, +and associates the method with the receiver's base type. 

    -MethodDecl   = "func" Receiver MethodName Signature [ Body ] .
+MethodDecl   = "func" Receiver MethodName ( Function | Signature ) .
 Receiver     = "(" [ identifier ] [ "*" ] BaseTypeName ")" .
 BaseTypeName = identifier .
    @@ -2284,12 +2295,11 @@ noteFrequency := map[string]float32{

    Function literals

    -A function literal represents an anonymous function. -It consists of a specification of the function type and a function body. +A function literal represents an anonymous function. 

    -FunctionLit = FunctionType Body .
+FunctionLit = "func" Function .
 
    @@ -3843,6 +3853,84 @@ Statement =
 SimpleStmt = EmptyStmt | ExpressionStmt | SendStmt | IncDecStmt | Assignment | ShortVarDecl .
    +

    Terminating statements

    + +

    +A terminating statement is one of the following: +

    + +
      +
    1. + A "return" or + "goto" statement. + +
      +
      2. + +
    2. + A call to the built-in function + panic. + +
      +
      3. + +
    3. + A block in which the statement list ends in a terminating statement. + +
      +
      4. + +
    4. + An "if" statement in which: +
        +
      • the "else" branch is present, and
        • +
      • both branches are terminating statements.
        • +
      +
      5. + +
    5. + A "for" statement in which: +
        +
      • there are no "break" statements referring to the "for" statement, and
        • +
      • the loop condition is absent.
        • +
      +
      6. + +
    6. + A "switch" statement in which: +
        +
      • there are no "break" statements referring to the "switch" statement,
        • +
      • there is a default case, and
        • +
      • the statement lists in each case, including the default, end in a terminating + statement, or a possibly labeled "fallthrough" + statement.
        • +
      +
      7. + +
    7. + A "select" statement in which: +
        +
      • there are no "break" statements referring to the "select" statement, and
        • +
      • the statement lists in each case, including the default if present, + end in a terminating statement.
        • +
      +
      8. + +
    8. + A labeled statement labeling + a terminating statement. +
      9. +
    + +

    +All other statements are not terminating. +

    + +

    +A statement list ends in a terminating statement if the list +is not empty and its final statement is terminating. +

    +

    Empty statements

    @@ -4149,7 +4237,7 @@ the expression true. 
     ExprSwitchStmt = "switch" [ SimpleStmt ";" ] [ Expression ] "{" { ExprCaseClause } "}" .
-ExprCaseClause = ExprSwitchCase ":" { Statement ";" } .
+ExprCaseClause = ExprSwitchCase ":" StatementList .
 ExprSwitchCase = "case" ExpressionList | "default" .
    @@ -4213,7 +4301,7 @@ expression x. As with type assertions, x must be of 
     TypeSwitchStmt  = "switch" [ SimpleStmt ";" ] TypeSwitchGuard "{" { TypeCaseClause } "}" .
 TypeSwitchGuard = [ identifier ":=" ] PrimaryExpr "." "(" "type" ")" .
-TypeCaseClause  = TypeSwitchCase ":" { Statement ";" } .
+TypeCaseClause  = TypeSwitchCase ":" StatementList .
 TypeSwitchCase  = "case" TypeList | "default" .
 TypeList        = Type { "," Type } .
    @@ -4536,7 +4624,7 @@ cases all referring to communication operations. 
     SelectStmt = "select" "{" { CommClause } "}" .
-CommClause = CommCase ":" { Statement ";" } .
+CommClause = CommCase ":" StatementList .
 CommCase   = "case" ( SendStmt | RecvStmt ) | "default" .
 RecvStmt   = [ ExpressionList "=" | IdentifierList ":=" ] RecvExpr .
 RecvExpr   = Expression .
-- 
2.48.1