fixes #1152
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2 changed files with 48 additions and 32 deletions
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@ -77,38 +77,6 @@ Once bound, typedesc params can appear in the rest of the proc signature:
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declareVariableWithType int, 42
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When used with macros and .compileTime. procs on the other hand, the compiler
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does not need to instantiate the code multiple times, because types then can be
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manipulated using the unified internal symbol representation. In such context
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typedesc acts as any other type. One can create variables, store typedesc
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values inside containers and so on. For example, here is how one can create
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a type-safe wrapper for the unsafe `printf` function from C:
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.. code-block:: nim
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macro safePrintF(formatString: string{lit}, args: varargs[expr]): expr =
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var i = 0
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for c in formatChars(formatString):
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var expectedType = case c
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of 'c': char
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of 'd', 'i', 'x', 'X': int
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of 'f', 'e', 'E', 'g', 'G': float
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of 's': string
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of 'p': pointer
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else: EOutOfRange
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var actualType = args[i].getType
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inc i
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if expectedType == EOutOfRange:
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error c & " is not a valid format character"
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elif expectedType != actualType:
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error "type mismatch for argument ", i, ". expected type: ",
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expectedType.name, ", actual type: ", actualType.name
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# keep the original callsite, but use cprintf instead
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result = callsite()
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result[0] = newIdentNode(!"cprintf")
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Overload resolution can be further influenced by constraining the set of
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types that will match the typedesc param:
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