[clang-tidy] 'implicit cast' -> 'implicit conversion'

Summary:
This patch renames checks, check options and changes messages to use correct
term "implicit conversion" instead of "implicit cast" (which has been in use in
Clang AST since ~10 years, but it's still technically incorrect w.r.t. C++
standard).

  * performance-implicit-cast-in-loop -> performance-implicit-conversion-in-loop
  * readability-implicit-bool-cast -> readability-implicit-bool-conversion
    - readability-implicit-bool-cast.AllowConditionalIntegerCasts ->
      readability-implicit-bool-conversion.AllowIntegerConditions
    - readability-implicit-bool-cast.AllowConditionalPointerCasts ->
      readability-implicit-bool-conversion.AllowPointerConditions

Reviewers: hokein, jdennett

Reviewed By: hokein

Subscribers: mgorny, JDevlieghere, xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D36456

llvm-svn: 310366

1 files changed, 21 insertions, 0 deletions

diff --git a/clang-tools-extra/docs/clang-tidy/checks/performance-implicit-conversion-in-loop.rst b/clang-tools-extra/docs/clang-tidy/checks/performance-implicit-conversion-in-loop.rst
new file mode 100644
index 00000000000..14e4d31f974
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/performance-implicit-conversion-in-loop.rst
@@ -0,0 +1,21 @@
+.. title:: clang-tidy - performance-implicit-conversion-in-loop
+
+performance-implicit-conversion-in-loop
+=======================================
+
+This warning appears in a range-based loop with a loop variable of const ref
+type where the type of the variable does not match the one returned by the
+iterator. This means that an implicit conversion happens, which can for example
+result in expensive deep copies.
+
+Example:
+
+.. code-block:: c++
+
+  map<int, vector<string>> my_map;
+  for (const pair<int, vector<string>>& p : my_map) {}
+  // The iterator type is in fact pair<const int, vector<string>>, which means
+  // that the compiler added a conversion, resulting in a copy of the vectors.
+
+The easiest solution is usually to use ``const auto&`` instead of writing the
+type manually.