diff options
| -rw-r--r-- | lib/pure/typetraits.nim | 36 | ||||
| -rw-r--r-- | tests/metatype/ttypetraits.nim | 7 |
2 files changed, 25 insertions, 18 deletions
diff --git a/lib/pure/typetraits.nim b/lib/pure/typetraits.nim index 7b6c94cbd..993d00e83 100644 --- a/lib/pure/typetraits.nim +++ b/lib/pure/typetraits.nim @@ -28,29 +28,32 @@ proc arity*(t: typedesc): int {.magic: "TypeTrait".} = assert arity(array[3, int]) == 2 assert arity((int, int, float, string)) == 4 -proc genericHead*(t: typedesc): typedesc {.magic: "TypeTrait".} +proc genericHead*(t: typedesc): typedesc {.magic: "TypeTrait".} = ## Accepts an instantiated generic type and returns its ## uninstantiated form. - ## - ## For example: - ## * `seq[int].genericHead` will be just `seq` - ## * `seq[int].genericHead[float]` will be `seq[float]` - ## ## A compile-time error will be produced if the supplied type ## is not generic. ## ## See also: ## * `stripGenericParams <#stripGenericParams,typedesc>`_ - ## - ## Example: - ## - ## .. code-block:: nim - ## type - ## Functor[A] = concept f - ## type MatchedGenericType = genericHead(typeof(f)) - ## # `f` will be a value of a type such as `Option[T]` - ## # `MatchedGenericType` will become the `Option` type - + runnableExamples: + type + Foo[T] = object + FooInst = Foo[int] + Foo2 = genericHead(FooInst) + doAssert Foo2 is Foo and Foo is Foo2 + doAssert genericHead(Foo[seq[string]]) is Foo + doAssert not compiles(genericHead(int)) + + type Generic = concept f + type _ = genericHead(typeof(f)) + proc bar(a: Generic): typeof(a) = a + doAssert bar(Foo[string].default) == Foo[string]() + doAssert not compiles bar(string.default) + + when false: # these don't work yet + doAssert genericHead(Foo[int])[float] is Foo[float] + doAssert seq[int].genericHead is seq proc stripGenericParams*(t: typedesc): typedesc {.magic: "TypeTrait".} ## This trait is similar to `genericHead <#genericHead,typedesc>`_, but @@ -168,7 +171,6 @@ macro genericParamsImpl(T: typedesc): untyped = ret = newTree(nnkBracketExpr, @[bindSym"range", ai]) else: since (1, 1): - echo ai.typeKind ret = newTree(nnkBracketExpr, @[bindSym"StaticParam", ai]) result.add ret break diff --git a/tests/metatype/ttypetraits.nim b/tests/metatype/ttypetraits.nim index 326faac82..32cdd2871 100644 --- a/tests/metatype/ttypetraits.nim +++ b/tests/metatype/ttypetraits.nim @@ -282,7 +282,12 @@ block genericHead: doAssert not compiles(genericHead(Foo)) type Bar = object doAssert not compiles(genericHead(Bar)) - # doAssert seq[int].genericHead is seq + + when false: # xxx not supported yet + doAssert seq[int].genericHead is seq + when false: # xxx not supported yet, gives: Error: identifier expected + type Hoo[T] = object + doAssert genericHead(Hoo[int])[float] is Hoo[float] block: # elementType iterator myiter(n: int): auto = |