[PATCH] D55245: [clang-tidy] Add the abseil-duration-subtraction check

[Hyrum Wright via Phabricator via cfe-commits]

hwright added inline comments.


================
Comment at: clang-tidy/abseil/DurationRewriter.cpp:35
+getInverseForScale(DurationScale Scale) {
+  static const std::unordered_map<DurationScale,
+                                  std::pair<llvm::StringRef, llvm::StringRef>>
----------------
lebedev.ri wrote:
> hwright wrote:
> > lebedev.ri wrote:
> > > https://llvm.org/docs/ProgrammersManual.html#other-map-like-container-options
> > > > We never use hash_set and unordered_set because they are generally very expensive (each insertion requires a malloc) and very non-portable.
> > > 
> > > Since the key is an enum, [[ https://llvm.org/docs/ProgrammersManual.html#llvm-adt-indexedmap-h | `llvm/ADT/IndexedMap.h` ]] should be a much better fit.
> > It doesn't look like `IndexedMap` has a constructor which takes an initializer list.  Without it, this code get a bit more difficult to read, and I'd prefer to optimize for readability here.
> The manual still 'recommends' not to use them.
> Simple solution: immediately invoked lambda
> Better solution: try to add such constructor to `IndexedMap`.
In hopes of not making this too much of a yak shave, I've gone with the immediately invoked lambda.


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Comment at: clang-tidy/abseil/DurationRewriter.cpp:74
+                     Node, *Result.Context))) {
+    return tooling::fixit::getText(*MaybeCallArg, *Result.Context).str();
+  }
----------------
lebedev.ri wrote:
> hwright wrote:
> > lebedev.ri wrote:
> > > So you generate fix-it, and then immediately degrade it into a string. Weird.
> > This doesn't generate a fix-it, it just fetches the text of the given node as a `StringRef` but we're returning a `string`, so we need to convert.
> > 
> > Is there a more canonical method I should use to fetch a node's text?
> I don't know the answer, but have you tried looking what `tooling::fixit::getText()` does internally?
I have.  It calls `internal::getText`, which, from the namespace, I'm hesitant to call in this context.


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Comment at: clang-tidy/abseil/DurationRewriter.cpp:156
+llvm::Optional<DurationScale> getScaleForInverse(llvm::StringRef Name) {
+  static const llvm::DenseMap<llvm::StringRef, DurationScale> ScaleMap(
+      {{"ToDoubleHours", DurationScale::Hours},
----------------
lebedev.ri wrote:
> Are you very sure this shouldn't be [[ https://llvm.org/docs/ProgrammersManual.html#llvm-adt-stringmap-h | `StringMap` ]]?
Nope.  Thanks for the catch!


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https://reviews.llvm.org/D55245