tmp/tmpdl_ubr1g/{from.md → to.md}
RENAMED
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### [[over]]: overloading <a id="diff.cpp17.over">[[diff.cpp17.over]]</a>
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**Change:** Equality and inequality expressions can now find reversed
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and rewritten candidates. **Rationale:** Improve consistency of equality
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with three-way comparison and make it easier to write the full
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complement of equality operations. **Effect on original feature:**
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-
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-
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``` cpp
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struct A {
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operator int() const;
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};
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@@ -23,5 +24,27 @@ int check(A x, A y) {
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(10 == x) + // calls #1, previously selected #2
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(10 != x); // calls #1, previously selected #3
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}
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```
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### [[over]]: overloading <a id="diff.cpp17.over">[[diff.cpp17.over]]</a>
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**Change:** Equality and inequality expressions can now find reversed
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and rewritten candidates. **Rationale:** Improve consistency of equality
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with three-way comparison and make it easier to write the full
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+
complement of equality operations. **Effect on original feature:** For
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certain pairs of types where one is convertible to the other, equality
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or inequality expressions between an object of one type and an object of
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the other type invoke a different operator. Also, for certain types,
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equality or inequality expressions between two objects of that type
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become ambiguous. For example:
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``` cpp
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struct A {
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operator int() const;
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};
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(10 == x) + // calls #1, previously selected #2
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(10 != x); // calls #1, previously selected #3
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}
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```
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**Change:** Overload resolution may change for equality operators
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[[expr.eq]]. **Rationale:** Support calling `operator==` with reversed
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order of arguments. **Effect on original feature:** Valid C++17 code
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that uses equality operators with conversion functions may be ill-formed
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or have different semantics in this revision of C++. For example:
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``` cpp
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struct A {
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operator int() const { return 10; }
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};
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bool operator==(A, int); // #1
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// #2 is built-in candidate: bool operator==(int, int);
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bool b = 10 == A(); // calls #1 with reversed order of arguments; previously selected #2
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struct B {
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bool operator==(const B&); // member function with no cv-qualifier
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};
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B b1;
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bool eq = (b1 == b1); // ambiguous; previously well-formed
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```
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