debian-packages/taggedalgebraic
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Avoid instantiating generic visitor with types it cannot handle.

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In cases where statically typed visitors need to be defined to avoid compile errors in a generic visitor, the generic one was still instantiated with the types already handled by the statically typed one(s), possibly resulting in a compile error.
This commit is contained in:
Sönke Ludwig 2020-04-04 11:19:40 +02:00
parent f9eb5878ad
commit 7a6da0ff79
1 changed files with 11 additions and 1 deletions
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12
source/taggedalgebraic/visit.d
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@ -217,7 +217,7 @@ private template matchesType(alias fun) {
else static if (Params.length == 1 && is(T == Params[0])) enum matchesType = true;
else enum matchesType = false;
} else static if (!isUnitType!T) {
static if (isSomeFunction!(fun!T)) {
static if (__traits(compiles, fun!T) && isSomeFunction!(fun!T)) {
alias Params = ParameterTypeTuple!(fun!T);
static if (Params.length == 1 && is(T == Params[0])) enum matchesType = true;
else enum matchesType = false;
@ -226,6 +226,16 @@ private template matchesType(alias fun) {
}
}
unittest {
class C {}
alias mt1 = matchesType!((C c) => true);
alias mt2 = matchesType!((c) { static assert(!is(typeof(c) == C)); });
static assert(mt1!C);
static assert(!mt1!int);
static assert(mt2!int);
static assert(!mt2!C);
}
private template selectHandler(T, VISITORS...)
{
import std.traits : ParameterTypeTuple, isSomeFunction;