[PATCH] D113796: Support: Make VarStreamArrayIterator::operator*() const-qualified

[Duncan P. N. Exon Smith via Phabricator via llvm-commits]

dexonsmith created this revision.
dexonsmith added reviewers: dblaikie, amccarth, zturner.
dexonsmith requested review of this revision.
Herald added a project: LLVM.

VarStreamArrayIterator returns a reference to a just-computed internal
value; since it's an iterator over `ValueType`, change `operator*()` to
always return `ValueType&`.

This patch is conservative in case it's useful to `std::move()` out an
extracted value...

But another option is to change it to iterate over `const ValueType`
and always return `const ValueType&`:

  ... : iterator_facade_base<..., const ValueType>

It only requires a one-line change to ExplainOutputStyle.cpp to get tests
compiling and passing:

  -  DbiModuleDescriptor &Descriptor = *Prev;
  +  const DbiModuleDescriptor &Descriptor = *Prev;

Based on 175d70ee5c2f03f640151488f5f33b7bd9b96f8d, perhaps that would
better match the original intent? @amccarth, @zturner, thoughts?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113796

Files:
  llvm/include/llvm/Support/BinaryStreamArray.h


Index: llvm/include/llvm/Support/BinaryStreamArray.h
===================================================================
--- llvm/include/llvm/Support/BinaryStreamArray.h
+++ llvm/include/llvm/Support/BinaryStreamArray.h
@@ -192,12 +192,7 @@
     return false;
   }
 
-  const ValueType &operator*() const {
-    assert(Array && !HasError);
-    return ThisValue;
-  }
-
-  ValueType &operator*() {
+  ValueType &operator*() const {
     assert(Array && !HasError);
     return ThisValue;
   }
@@ -242,7 +237,7 @@
       *HadError = true;
   }
 
-  ValueType ThisValue;
+  mutable ValueType ThisValue;
   BinaryStreamRef IterRef;
   Extractor Extract;
   const ArrayType *Array{nullptr};


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