courbet added a comment.
Thanks for the comments.
================
Comment at: clang-tidy/cppcoreguidelines/SlicingCheck.cpp:48
@@ +47,3 @@
+
+ // Assignement slicing: "a = b;" and "a = std::move(b);" variants.
+ const auto SlicesObjectInAssignment =
----------------
hokein wrote:
> Looks like you are missing some cases here, like assigning a Subclass object
> from a function call to a Baseclass object, passing a Subclass object to a
> function whose parameter is a BaseClass.
>
> But I think it's fine to implement in a separate patch, but you'd better to
> add a TODO here.
>
> ```
> SubClass f1();
> BaseClass a = f1();
>
> void f1(BaseClass a);
> SubClass sc;
> f1(sc);
> ```
Actually these will still create a CXXConstructExpr in the AST, e.g for case
(2):
```
CallExpr 0x3d6e560 </usr/local/google/home/courbet/test2.cc:10:3, col:6> 'void'
|-ImplicitCastExpr 0x3d6e548 <col:3> 'void (*)(class A)'
<FunctionToPointerDecay>
| `-DeclRefExpr 0x3d6e4f8 <col:3> 'void (class A)' lvalue Function 0x3d66550
'g' 'void (class A)'
`-CXXConstructExpr 0x3d6e5c8 <col:5> 'class A' 'void (const class A &) throw()'
`-ImplicitCastExpr 0x3d6e5b0 <col:5> 'const class A' lvalue <NoOp>
`-ImplicitCastExpr 0x3d6e590 <col:5> 'class A' lvalue <DerivedToBase (A)>
`-DeclRefExpr 0x3d6e4d0 <col:5> 'class B' lvalue Var 0x3d6e300 'b' 'class
B'
```
I alreagy have a test to case (2) and I've added one for case (1).
================
Comment at: clang-tidy/cppcoreguidelines/SlicingCheck.cpp:84
@@ +83,3 @@
+ diag(Call.getExprLoc(),
+ "slicing object from type %0 to %1 discards override %2")
+ << &DerivedDecl << &BaseDecl << Method;
----------------
hokein wrote:
> There are two diagnostic messages in the code. For subclasses with override
> base class methods and extra member, this will print two messages, which is a
> bit of redundant.
I think we still want to point out to the user which overrides are going to be
discarded:
class A { virtual void f(); virtual void g(); }
class B : public A { void f() override; void g() override; int a; }
The messages will be:
"slicing object from type 'B' to 'A' discards override 'f' "
"slicing object from type 'B' to 'A' discards override 'g' "
"slicing object from type 'B' to 'A' discards 4*sizeof(char) bytes of state"
http://reviews.llvm.org/D21992
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