[llvm] [LLVM][ADT] Explicitly convert size_t values to SmallVector's size type (PR #77939)

[Andrew Browne via llvm-commits]

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@@ -468,7 +469,7 @@ void SmallVectorTemplateBase<T, TriviallyCopyable>::takeAllocationForGrow(
     free(this->begin());
 
   this->BeginX = NewElts;
-  this->Capacity = NewCapacity;
+  this->Capacity = static_cast<SmallVectorSizeType<T>>(NewCapacity);
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browneee wrote:

Should we add a `set_capacity(size_t)` method to `SmallVectorBase`, to make this cast a bit neater?

https://github.com/llvm/llvm-project/pull/77939