diff options
| -rw-r--r-- | compiler/semstmts.nim | 6 | ||||
| -rw-r--r-- | doc/manual/stmts.txt | 10 | ||||
| -rw-r--r-- | doc/tut1.txt | 2 | ||||
| -rw-r--r-- | web/news.txt | 5 |
4 files changed, 15 insertions, 8 deletions
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim index c386785be..063df30fd 100644 --- a/compiler/semstmts.nim +++ b/compiler/semstmts.nim @@ -199,11 +199,12 @@ proc semCase(c: PContext, n: PNode): PNode = var covered: BiggestInt = 0 var typ = commonTypeBegin var hasElse = false + var notOrdinal = false case skipTypes(n.sons[0].typ, abstractVarRange-{tyTypeDesc}).kind of tyInt..tyInt64, tyChar, tyEnum, tyUInt..tyUInt32, tyBool: chckCovered = true of tyFloat..tyFloat128, tyString, tyError: - discard + notOrdinal = true else: localError(n.info, errSelectorMustBeOfCertainTypes) return @@ -233,6 +234,9 @@ proc semCase(c: PContext, n: PNode): PNode = hasElse = true else: illFormedAst(x) + if notOrdinal and not hasElse: + message(n.info, warnDeprecated, + "use 'else: discard'; non-ordinal case without 'else'") if chckCovered: if covered == toCover(n.sons[0].typ): hasElse = true diff --git a/doc/manual/stmts.txt b/doc/manual/stmts.txt index b706101e1..1307ff917 100644 --- a/doc/manual/stmts.txt +++ b/doc/manual/stmts.txt @@ -262,13 +262,11 @@ given *slicelist* the ``else`` part is executed. If there is no ``else`` part and not all possible values that ``expr`` can hold occur in a ``slicelist``, a static error occurs. This holds only for expressions of ordinal types. "All possible values" of ``expr`` are determined by ``expr``'s -type. +type. To suppress the static error an ``else`` part with an +empty ``discard`` statement should be used. -If the expression is not of an ordinal type, and no ``else`` part is -given, control passes after the ``case`` statement. - -To suppress the static error in the ordinal case an ``else`` part with an -empty ``discard`` statement can be used. +For non ordinal types it is not possible to list every possible value and so +these always require an ``else`` part. As a special semantic extension, an expression in an ``of`` branch of a case statement may evaluate to a set or array constructor; the set or array is then diff --git a/doc/tut1.txt b/doc/tut1.txt index 2a836190c..950f758f1 100644 --- a/doc/tut1.txt +++ b/doc/tut1.txt @@ -312,7 +312,7 @@ the compiler that for every other value nothing should be done: The empty `discard statement`_ is a *do nothing* statement. The compiler knows that a case statement with an else part cannot fail and thus the error disappears. Note that it is impossible to cover all possible string values: -that is why there is no such check for string cases. +that is why string cases always need an ``else`` branch. In general the case statement is used for subrange types or enumerations where it is of great help that the compiler checks that you covered any possible diff --git a/web/news.txt b/web/news.txt index 93cb71f94..233a8e2c7 100644 --- a/web/news.txt +++ b/web/news.txt @@ -47,11 +47,16 @@ News found under the `nim-code <https://github.com/nimrod-code>`_ organisation. - Removed the deprecated ``web`` module, the ``httpclient`` module should be used instead. + - String case (or any non-ordinal case) statements + without 'else' are deprecated. + Language Additions ------------------ - There is a new ``parallel`` statement for safe fork&join parallel computing. + - ``guard`` and ``lock`` pragmas have been implemented to support safer + concurrent programming. Library Additions |