Merge pull request #927 from ZachHenkel/master

Additional guidance around casts:

CppCoreGuidelines.md

@@ -11653,7 +11653,8 @@ Surprised? I'm just glad I didn't crash the program.
 
 ##### Note
 
-Programmer who write casts typically assumes that they know what they are doing.
+Programmers who write casts typically assume that they know what they are doing, 
+or that writing a cast makes the program "easier to read".
 In fact, they often disable the general rules for using values.
 Overload resolution and template instantiation usually pick the right function if there is a right function to pick.
 If there is not, maybe there ought to be, rather than applying a local fix (cast).
@@ -11670,18 +11671,19 @@ If you feel the need for a lot of casts, there may be a fundamental design probl
 
 ##### Alternatives
 
-Casts are widely (mis) used. Modern C++ has constructs that eliminate the need for casts in many contexts, such as
+Casts are widely (mis) used. Modern C++ has rules and constructs that eliminate the need for casts in many contexts, such as
 
 * Use templates
 * Use `std::variant`
-
+* Rely on the well defined, safe, implicit conversions between pointer types
 
 ##### Enforcement
 
 * Force the elimination of C-style casts
-* Warn against named casts
+* Warn if there are many functional style casts (there is an obvious problem in quantifying 'many')
-* Warn if there are many functional style casts (there is an obvious problem in quantifying 'many').
 * The [type profile](#Pro-type-reinterpretcast) bans `reinterpret_cast`.
+* Warn against [identity casts](#Pro-type-identitycast) between pointer types, where the source and target types are the same (#Pro-type-identitycast)
+* Warn if a pointer cast could be [implicit](#Pro-type-implicitpointercast)
 
 ### <a name="Res-casts-named"></a>ES.49: If you must use a cast, use a named cast
 
@@ -11743,6 +11745,7 @@ for example.)
 
 * Flag C-style and functional casts.
 * The [type profile](#Pro-type-reinterpretcast) bans `reinterpret_cast`.
+* The [type profile](#Pro-type-arithmeticcast) warns when using `static_cast` between arithmetic types.
 
 ### <a name="Res-casts-const"></a>ES.50: Don't cast away `const`
 
@@ -19589,8 +19592,11 @@ An implementation of this profile shall recognize the following patterns in sour
 
 Type safety profile summary:
 
-* <a name="Pro-type-reinterpretcast"></a>Type.1: Don't use `reinterpret_cast`:
+* <a name="Pro-type-avoidcasts"></a>Type.1: [Avoid casts](#Res-casts):  
-A strict version of [Avoid casts](#Res-casts) and [prefer named casts](#Res-casts-named).
+<a name="Pro-type-reinterpretcast">a. </a>Don't use `reinterpret_cast`; A strict version of [Avoid casts](#Res-casts) and [prefer named casts](#Res-casts-named).  
+<a name="Pro-type-arithmeticcast">b. </a>Don't use `static_cast` for arithmetic types; A strict version of [Avoid casts](#Res-casts) and [prefer named casts](#Res-casts-named).  
+<a name="Pro-type-identitycast">c. </a>Don't cast between pointer types where the source type and the target type are the same; A strict version of [Avoid casts](#Res-casts).
+<a name="Pro-type-implicitpointercast">d. </a>Don't cast between pointer types when the conversion could be implicit; A strict version of [Avoid casts](#Res-casts).
 * <a name="Pro-type-downcast"></a>Type.2: Don't use `static_cast` to downcast:
 [Use `dynamic_cast` instead](#Rh-dynamic_cast).
 * <a name="Pro-type-constcast"></a>Type.3: Don't use `const_cast` to cast away `const` (i.e., at all):

scripts/hunspell/isocpp.dic

@@ -42,6 +42,7 @@ archetypical
 arg
 argh
 args
+arithmeticcast
 arr2
 arrayindex
 ASIC
@@ -215,6 +216,7 @@ HTTP
 Hyslop
 i2
 IDE
+identitycast
 IDEs
 IEC
 ifdef
@@ -223,6 +225,7 @@ ifstream
 impactful
 impl
 Impl
+implicitpointercast
 incompleat
 increment1
 Incrementable