[PATCH] D59142: YAMLIO: Improve template arg deduction for mapOptional

[Zachary Turner via Phabricator via llvm-commits]

zturner added inline comments.


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Comment at: include/llvm/Support/YAMLTraits.h:896
                               Context &Ctx) {
-    this->processKeyWithDefault(Key, Val, Default, false, Ctx);
+    const T &DefaultAsT = Default; // Use only implicit conversions.
+    this->processKeyWithDefault(Key, Val, DefaultAsT, false, Ctx);
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Another possibility is `static_assert(std::is_convertible<T, DefaultT>::value, "Default type must be implicitly convertible to value type!");`  which should have the same effect, and also yield a better compiler error message.  Then, since explicit conversions are disallowed by the `static_assert`, you could re-write the call site as `this->processKeyWithDefault(Key, Val, static_cast<T>(Default), false, Ctx);`

I don't have a strong preference, but this feels mildly better to me.  WDYT?


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59142/new/

https://reviews.llvm.org/D59142