From Jason Turner

[diff.cpp17.lex]

C++20 → C++23 3.2 KB 26 lines
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Archived: C++20 | C++23
Markdown: C++20 | C++23
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  1. tmp/tmpofqxam4a/{from.md → to.md} +7 -14
tmp/tmpofqxam4a/{from.md → to.md} RENAMED
@@ -1,41 +1,33 @@
1
  ### [[lex]]: lexical conventions <a id="diff.cpp17.lex">[[diff.cpp17.lex]]</a>
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  **Change:** New identifiers with special meaning. **Rationale:**
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  Required for new features. **Effect on original feature:** Logical lines
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  beginning with `module` or `import` may be interpreted differently in
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- this International Standard.
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-
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- [*Example 1*:
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  ``` cpp
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  class module {};
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  module m1; // was variable declaration; now module-declaration
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  module *m2; // variable declaration
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  class import {};
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- import j1; // was variable declaration; now import-declaration
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  ::import j2; // variable declaration
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  ```
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- — *end example*]
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-
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  **Change:** *header-name* tokens are formed in more contexts.
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  **Rationale:** Required for new features. **Effect on original
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  feature:** When the identifier `import` is followed by a `<` character,
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- a *header-name* token may be formed.
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-
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- [*Example 2*:
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  ``` cpp
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  template<typename> class import {};
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  import<int> f(); // ill-formed; previously well-formed
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  ::import<int> g(); // OK
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  ```
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- — *end example*]
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-
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  **Change:** New keywords. **Rationale:** Required for new features.
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  - The `char8_t` keyword is added to differentiate the types of ordinary
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  and UTF-8 literals [[lex.string]].
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  - The `concept` keyword is added to enable the definition of concepts
@@ -50,16 +42,17 @@ import<int> f(); // ill-formed; previously well-formed
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  *requires-clause* [[temp.pre]] or a *requires-expression*
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  [[expr.prim.req]].
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  Valid C++17 code using `char8_t`, `concept`, `consteval`, `constinit`,
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  `co_await`, `co_yield`, `co_return`, or `requires` as an identifier is
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- not valid in this International Standard.
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  **Change:** New operator `<=>`. **Rationale:** Necessary for new
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  functionality. **Effect on original feature:** Valid C++17 code that
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  contains a `<=` token immediately followed by a `>` token may be
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- ill-formed or have different semantics in this International Standard:
 
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  ``` cpp
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  namespace N {
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  struct X {};
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  bool operator<=(X, X);
@@ -72,11 +65,11 @@ namespace N {
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  Required for new features. The changed types enable function
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  overloading, template specialization, and type deduction to distinguish
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  ordinary and UTF-8 string and character literals. **Effect on original
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  feature:** Valid C++17 code that depends on UTF-8 string literals having
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  type “array of `const char`” and UTF-8 character literals having type
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- “`char`” is not valid in this International Standard.
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  ``` cpp
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  const auto *u8s = u8"text"; // u8s previously deduced as const char*; now deduced as const char8_t*
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  const char *ps = u8s; // ill-formed; previously well-formed
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1
  ### [[lex]]: lexical conventions <a id="diff.cpp17.lex">[[diff.cpp17.lex]]</a>
2
 
3
  **Change:** New identifiers with special meaning. **Rationale:**
4
  Required for new features. **Effect on original feature:** Logical lines
5
  beginning with `module` or `import` may be interpreted differently in
6
+ this revision of C++. For example:
 
 
7
 
8
  ``` cpp
9
  class module {};
10
  module m1; // was variable declaration; now module-declaration
11
  module *m2; // variable declaration
12
 
13
  class import {};
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+ import j1; // was variable declaration; now module-import-declaration
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  ::import j2; // variable declaration
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  ```
17
 
 
 
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  **Change:** *header-name* tokens are formed in more contexts.
19
  **Rationale:** Required for new features. **Effect on original
20
  feature:** When the identifier `import` is followed by a `<` character,
21
+ a *header-name* token may be formed. For example:
 
 
22
 
23
  ``` cpp
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  template<typename> class import {};
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  import<int> f(); // ill-formed; previously well-formed
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  ::import<int> g(); // OK
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  ```
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29
  **Change:** New keywords. **Rationale:** Required for new features.
30
 
31
  - The `char8_t` keyword is added to differentiate the types of ordinary
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  and UTF-8 literals [[lex.string]].
33
  - The `concept` keyword is added to enable the definition of concepts
 
42
  *requires-clause* [[temp.pre]] or a *requires-expression*
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  [[expr.prim.req]].
44
 
45
  Valid C++17 code using `char8_t`, `concept`, `consteval`, `constinit`,
46
  `co_await`, `co_yield`, `co_return`, or `requires` as an identifier is
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+ not valid in this revision of C++.
48
 
49
  **Change:** New operator `<=>`. **Rationale:** Necessary for new
50
  functionality. **Effect on original feature:** Valid C++17 code that
51
  contains a `<=` token immediately followed by a `>` token may be
52
+ ill-formed or have different semantics in this revision of C++. For
53
+ example:
54
 
55
  ``` cpp
56
  namespace N {
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  struct X {};
58
  bool operator<=(X, X);
 
65
  Required for new features. The changed types enable function
66
  overloading, template specialization, and type deduction to distinguish
67
  ordinary and UTF-8 string and character literals. **Effect on original
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  feature:** Valid C++17 code that depends on UTF-8 string literals having
69
  type “array of `const char`” and UTF-8 character literals having type
70
+ “`char`” is not valid in this revision of C++. For example:
71
 
72
  ``` cpp
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  const auto *u8s = u8"text"; // u8s previously deduced as const char*; now deduced as const char8_t*
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  const char *ps = u8s; // ill-formed; previously well-formed
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