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- discard """
- action: compile
- errormsg: "writeSomething() has an illegal effect: WriteIO"
- line: 19
- """
- type
- IO = object of RootEffect ## input/output effect
- ReadIO = object of IO ## input effect
- WriteIO = object of IO ## output effect
- proc readSomething(): string {.tags: [ReadIO].} = ""
- proc writeSomething(): void {.tags: [WriteIO].} = echo "..."
- proc noWritesPlease() {.forbids: [WriteIO].} =
- # this is OK:
- echo readSomething()
- # the compiler prevents this:
- writeSomething()
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