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

[Andrei Golubev via llvm-commits]

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@@ -99,8 +99,9 @@ template <class Size_T> class SmallVectorBase {
   ///
   /// This does not construct or destroy any elements in the vector.
   void set_size(size_t N) {
-    assert(N <= capacity());
-    Size = N;
+    auto n = static_cast<Size_T>(N);
+    assert(n <= capacity());
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andrey-golubev wrote:

> capacity() also returns size_t, so probably better to keep the assertion first.

good point. I'm not sure why our downstream had it differently. "reverted" this part back.

overall, rewrote this part as per @browneee 's advice. I think it makes sense to keep the `assert(static_cast<size_t>(Size) == N);` at the end as well. if anything, it's a function's postcondition validation so should be no harm (also, wondering if it might actually catch any data-losing `size_t -> uint32_t` narrowings).


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