[Clang][Diagnostics] Use "structured binding" instead of "decomposition"

P0615R0 changed the term "decomposition" to "structured binding".
Some diagnostic messages were created before this paper.
These messages should be updated using "structured binding" to avoid making users confused.

See for context:
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0615r0.html

Author: foxfromabyss

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -504,9 +504,10 @@ def err_expected_end_of_enumerator : Error<
 def err_expected_coloncolon_after_super : Error<
   "expected '::' after '__super'">;
 
-def ext_decomp_decl_empty : ExtWarn<
-  "ISO C++17 does not allow a decomposition group to be empty">,
-  InGroup<DiagGroup<"empty-decomposition">>;
+def ext_decomp_decl_empty
+    : ExtWarn<
+          "ISO C++17 does not allow a structured binding group to be empty">,
+      InGroup<DiagGroup<"empty-structured-binding">>;
 
 def err_function_parameter_limit_exceeded : Error<
   "too many function parameters; subsequent parameters will be ignored">;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -31,12 +31,12 @@ defm constexpr_body_multiple_return : CXX14Compat<
 defm variable_template : CXX14Compat<"variable templates are">;
 
 // C++17 compatibility with C++14 and earlier.
-defm decomp_decl : CXX17Compat<"decomposition declarations are">;
+defm decomp_decl : CXX17Compat<"structured binding declarations are">;
 defm inline_variable : CXX17Compat<"inline variables are">;
 
 // C++20 compatibility with C++17 and earlier.
 defm decomp_decl_spec
-    : CXX20Compat<"decomposition declaration declared '%0' is">;
+    : CXX20Compat<"structured binding declaration declared '%0' is">;
 defm constexpr_local_var_no_init : CXX20Compat<
   "uninitialized variable in a constexpr %select{function|constructor}0 is">;
 defm constexpr_function_try_block : CXX20Compat<
@@ -589,60 +589,59 @@ def warn_modifying_shadowing_decl :
           "field of %1">,
   InGroup<ShadowFieldInConstructorModified>, DefaultIgnore;
 
-// C++ decomposition declarations
-def err_decomp_decl_context : Error<
-  "decomposition declaration not permitted in this context">;
+// C++ structured binding declarations
+def err_decomp_decl_context
+    : Error<"structured binding declaration not permitted in this context">;
 def err_decomp_decl_spec
-    : Error<"decomposition declaration cannot be declared '%0'">;
-def err_decomp_decl_type : Error<
-  "decomposition declaration cannot be declared with type %0; "
-  "declared type must be 'auto' or reference to 'auto'">;
-def err_decomp_decl_constraint : Error<
-  "decomposition declaration cannot be declared with constrained 'auto'">;
-def err_decomp_decl_parens : Error<
-  "decomposition declaration cannot be declared with parentheses">;
-def err_decomp_decl_template : Error<
-  "decomposition declaration cannot be a template">;
-def err_decomp_decl_not_alone : Error<
-  "decomposition declaration must be the only declaration in its group">;
-def err_decomp_decl_requires_init : Error<
-  "decomposition declaration %0 requires an initializer">;
-def err_decomp_decl_wrong_number_bindings : Error<
-  "type %0 decomposes into %3 %plural{1:element|:elements}2, but "
-  "%select{%plural{0:no|:only %1}1|%1}4 "
-  "%plural{1:name was|:names were}1 provided">;
-def err_decomp_decl_unbindable_type : Error<
-  "cannot decompose %select{union|non-class, non-array}1 type %2">;
-def err_decomp_decl_multiple_bases_with_members : Error<
-  "cannot decompose class type %1: "
-  "%select{its base classes %2 and|both it and its base class}0 %3 "
-  "have non-static data members">;
-def err_decomp_decl_ambiguous_base : Error<
-  "cannot decompose members of ambiguous base class %1 of %0:%2">;
-def err_decomp_decl_inaccessible_base : Error<
-  "cannot decompose members of inaccessible base class %1 of %0">,
-  AccessControl;
-def err_decomp_decl_inaccessible_field : Error<
-  "cannot decompose %select{private|protected}0 member %1 of %3">,
-  AccessControl;
-def err_decomp_decl_lambda : Error<
-  "cannot decompose lambda closure type">;
-def err_decomp_decl_anon_union_member : Error<
-  "cannot decompose class type %0 because it has an anonymous "
-  "%select{struct|union}1 member">;
-def err_decomp_decl_std_tuple_element_not_specialized : Error<
-  "cannot decompose this type; 'std::tuple_element<%0>::type' "
-  "does not name a type">;
-def err_decomp_decl_std_tuple_size_not_constant : Error<
-  "cannot decompose this type; 'std::tuple_size<%0>::value' "
-  "is not a valid integral constant expression">;
+    : Error<"structured binding declaration cannot be declared '%0'">;
+def err_decomp_decl_type
+    : Error<"structured binding declaration cannot be declared with type %0; "
+            "declared type must be 'auto' or reference to 'auto'">;
+def err_decomp_decl_constraint : Error<"structured binding declaration cannot "
+                                       "be declared with constrained 'auto'">;
+def err_decomp_decl_parens
+    : Error<
+          "structured binding declaration cannot be declared with parentheses">;
+def err_decomp_decl_template
+    : Error<"structured binding declaration cannot be a template">;
+def err_decomp_decl_not_alone : Error<"structured binding declaration must be "
+                                      "the only declaration in its group">;
+def err_decomp_decl_requires_init
+    : Error<"structured binding declaration %0 requires an initializer">;
+def err_decomp_decl_wrong_number_bindings
+    : Error<"type %0 binds to %3 %plural{1:element|:elements}2, but "
+            "%select{%plural{0:no|:only %1}1|%1}4 "
+            "%plural{1:name was|:names were}1 provided">;
+def err_decomp_decl_unbindable_type
+    : Error<"cannot bind %select{union|non-class, non-array}1 type %2">;
+def err_decomp_decl_multiple_bases_with_members
+    : Error<"cannot bind class type %1: "
+            "%select{its base classes %2 and|both it and its base class}0 %3 "
+            "have non-static data members">;
+def err_decomp_decl_ambiguous_base
+    : Error<"cannot bind members of ambiguous base class %1 of %0:%2">;
+def err_decomp_decl_inaccessible_base
+    : Error<"cannot bind members of inaccessible base class %1 of %0">,
+      AccessControl;
+def err_decomp_decl_inaccessible_field
+    : Error<"cannot bind %select{private|protected}0 member %1 of %3">,
+      AccessControl;
+def err_decomp_decl_lambda : Error<"cannot bind lambda closure type">;
+def err_decomp_decl_anon_union_member
+    : Error<"cannot bind class type %0 because it has an anonymous "
+            "%select{struct|union}1 member">;
+def err_decomp_decl_std_tuple_element_not_specialized
+    : Error<"cannot bind this type; 'std::tuple_element<%0>::type' "
+            "does not name a type">;
+def err_decomp_decl_std_tuple_size_not_constant
+    : Error<"cannot bind this type; 'std::tuple_size<%0>::value' "
+            "is not a valid integral constant expression">;
 def err_decomp_decl_std_tuple_size_invalid
-    : Error<"cannot decompose this type; 'std::tuple_size<%0>::value' "
+    : Error<"cannot bind this type; 'std::tuple_size<%0>::value' "
             "is not a valid size: %1">;
 def note_in_binding_decl_init : Note<
   "in implicit initialization of binding declaration %0">;
-def err_arg_is_not_destructurable : Error<
-  "type %0 cannot be decomposed">;
+def err_arg_is_not_destructurable : Error<"type %0 cannot be bound">;
 
 def err_std_type_trait_not_class_template : Error<
   "unsupported standard library implementation: "
@@ -2618,9 +2617,9 @@ def err_auto_variable_cannot_appear_in_own_initializer
           "%VarTemplateExplicitSpec{variable template explicit "
           "specialization}}0 %1 "
           "declared with deduced type %2 cannot appear in its own initializer">;
-def err_binding_cannot_appear_in_own_initializer : Error<
-  "binding %0 cannot appear in the initializer of its own "
-  "decomposition declaration">;
+def err_binding_cannot_appear_in_own_initializer
+    : Error<"binding %0 cannot appear in the initializer of its own "
+            "structured binding declaration">;
 def err_new_array_of_auto : Error<
   "cannot allocate array of 'auto'">;
 def err_auto_not_allowed : Error<

clang/test/Analysis/zero-size-non-pod-array.cpp

@@ -95,7 +95,7 @@ void zeroSizeArrayBinding() {
     // Note: This is an error in gcc but a warning in clang.
     // In MSVC the declaration of 'S arr[0]' is already an error
     // and it doesn't recognize this syntax as a structured binding.
-    auto [] = arr; //expected-warning{{ISO C++17 does not allow a decomposition group to be empty}}
+    auto [] = arr; //expected-warning{{ISO C++17 does not allow a structured binding group to be empty}}
 
     clang_analyzer_eval(S::CtorInvocationCount == 0); //expected-warning{{TRUE}}
 }

clang/test/CXX/dcl.decl/dcl.decomp/p2.cpp

@@ -16,8 +16,8 @@ int array() {
   using X3 = X[3];
   auto [a3, b3, c3] = X3{1, 2, 3};
 
-  auto &[d, e] = arr; // expected-error {{type 'int[3]' decomposes into 3 elements, but only 2 names were provided}}
-  auto &[f, g, h, i] = arr; // expected-error {{type 'int[3]' decomposes into 3 elements, but 4 names were provided}}
+  auto &[d, e] = arr; // expected-error {{type 'int[3]' binds to 3 elements, but only 2 names were provided}}
+  auto &[f, g, h, i] = arr; // expected-error {{type 'int[3]' binds to 3 elements, but 4 names were provided}}
 
   auto &[r0, r1, r2] = arr;
   const auto &[cr0, cr1, cr2] = arr;

clang/test/CXX/dcl.decl/dcl.decomp/p3.cpp

@@ -5,26 +5,26 @@ using size_t = decltype(sizeof(0));
 struct A { int x, y; };
 struct B { int x, y; };
 
-void no_tuple_size_1() { auto [x, y] = A(); } // ok, decompose elementwise
+void no_tuple_size_1() { auto [x, y] = A(); } // ok, bind elementwise
 
 namespace std { template<typename T> struct tuple_size; }
-void no_tuple_size_2() { auto [x, y] = A(); } // ok, decompose elementwise
+void no_tuple_size_2() { auto [x, y] = A(); } // ok, bind elementwise
 
 struct Bad1 { int a, b; };
 template<> struct std::tuple_size<Bad1> {};
 void no_tuple_size_3() { auto [x, y] = Bad1(); } // ok, omitting value is valid after DR2386
 
 struct Bad2 {};
 template<> struct std::tuple_size<Bad2> { const int value = 5; };
-void no_tuple_size_4() { auto [x, y] = Bad2(); } // expected-error {{cannot decompose this type; 'std::tuple_size<Bad2>::value' is not a valid integral constant expression}}
+void no_tuple_size_4() { auto [x, y] = Bad2(); } // expected-error {{cannot bind this type; 'std::tuple_size<Bad2>::value' is not a valid integral constant expression}}
 
 template<> struct std::tuple_size<A> { static const int value = 3; };
 template<> struct std::tuple_size<B> { enum { value = 3 }; };
 
 void no_get_1() {
   {
-    auto [a0, a1] = A(); // expected-error {{decomposes into 3 elements}}
-    auto [b0, b1] = B(); // expected-error {{decomposes into 3 elements}}
+    auto [a0, a1] = A(); // expected-error {{binds to 3 elements}}
+    auto [b0, b1] = B(); // expected-error {{binds to 3 elements}}
   }
   auto [a0, a1, a2] = A(); // expected-error {{undeclared identifier 'get'}} expected-note {{in implicit initialization of binding declaration 'a0'}}
 }

clang/test/CXX/dcl.decl/dcl.decomp/p4.cpp

@@ -25,10 +25,10 @@ namespace NonPublicMembers {
   struct NonPublic4 : NonPublic2 {};
 
   void test() {
-    auto [a1] = NonPublic1(); // expected-error {{cannot decompose protected member 'a' of 'NonPublicMembers::NonPublic1'}}
-    auto [a2] = NonPublic2(); // expected-error {{cannot decompose private member 'a' of 'NonPublicMembers::NonPublic2'}}
-    auto [a3] = NonPublic3(); // expected-error {{cannot decompose members of inaccessible base class 'A' of 'NonPublicMembers::NonPublic3'}}
-    auto [a4] = NonPublic4(); // expected-error {{cannot decompose private member 'a' of 'NonPublicMembers::NonPublic2'}}
+    auto [a1] = NonPublic1(); // expected-error {{cannot bind protected member 'a' of 'NonPublicMembers::NonPublic1'}}
+    auto [a2] = NonPublic2(); // expected-error {{cannot bind private member 'a' of 'NonPublicMembers::NonPublic2'}}
+    auto [a3] = NonPublic3(); // expected-error {{cannot bind members of inaccessible base class 'A' of 'NonPublicMembers::NonPublic3'}}
+    auto [a4] = NonPublic4(); // expected-error {{cannot bind private member 'a' of 'NonPublicMembers::NonPublic2'}}
   }
 }
 
@@ -46,8 +46,8 @@ namespace AnonymousMember {
   };
 
   void test() {
-    auto [a1] = Struct(); // expected-error {{cannot decompose class type 'Struct' because it has an anonymous struct member}}
-    auto [a2] = Union(); // expected-error {{cannot decompose class type 'Union' because it has an anonymous union member}}
+    auto [a1] = Struct(); // expected-error {{cannot bind class type 'Struct' because it has an anonymous struct member}}
+    auto [a2] = Union(); // expected-error {{cannot bind class type 'Union' because it has an anonymous union member}}
   }
 }
 
@@ -73,12 +73,12 @@ namespace MultipleClasses {
   struct M : virtual J, L {};
 
   void test() {
-    auto [b] = B(); // expected-error {{cannot decompose class type 'B': both it and its base class 'A' have non-static data members}}
-    auto [d] = D(); // expected-error {{cannot decompose class type 'D': its base classes 'A' and 'C' have non-static data members}}
+    auto [b] = B(); // expected-error {{cannot bind class type 'B': both it and its base class 'A' have non-static data members}}
+    auto [d] = D(); // expected-error {{cannot bind class type 'D': its base classes 'A' and 'C' have non-static data members}}
     auto [e] = E();
-    auto [f] = F(); // expected-error-re {{cannot decompose members of ambiguous base class 'A' of 'F':{{.*}}struct MultipleClasses::F -> A{{.*}}struct MultipleClasses::F -> E -> A}}
+    auto [f] = F(); // expected-error-re {{cannot bind members of ambiguous base class 'A' of 'F':{{.*}}struct MultipleClasses::F -> A{{.*}}struct MultipleClasses::F -> E -> A}}
     auto [h] = H(); // ok, only one (virtual) base subobject even though there are two paths to it
-    auto [k] = K(); // expected-error {{cannot decompose members of ambiguous base class 'I'}}
+    auto [k] = K(); // expected-error {{cannot bind members of ambiguous base class 'I'}}
     auto [m] = M(); // ok, all paths to I are through the same virtual base subobject J
 
     same<decltype(m), int>();
@@ -214,7 +214,7 @@ namespace p0969r0 {
     auto &[x, y] = b;
   }
   void test_external(B b) {
-    auto &[x, y] = b; // expected-error {{cannot decompose members of inaccessible base class 'A' of 'p0969r0::B'}}
+    auto &[x, y] = b; // expected-error {{cannot bind members of inaccessible base class 'A' of 'p0969r0::B'}}
   }
 
   struct C {
@@ -229,13 +229,13 @@ namespace p0969r0 {
   struct D : C {
     static void test_member(D d, C c) {
       auto &[x1, y1] = d;
-      auto &[x2, y2] = c; // expected-error {{cannot decompose protected member 'y' of 'p0969r0::C'}}
+      auto &[x2, y2] = c; // expected-error {{cannot bind protected member 'y' of 'p0969r0::C'}}
     }
   };
   void test_friend(D d) {
     auto &[x, y] = d;
   }
   void test_external(D d) {
-    auto &[x, y] = d; // expected-error {{cannot decompose protected member 'y' of 'p0969r0::C'}}
+    auto &[x, y] = d; // expected-error {{cannot bind protected member 'y' of 'p0969r0::C'}}
   }
 }

clang/test/CXX/drs/cwg22xx.cpp

@@ -202,7 +202,7 @@ namespace cwg2285 { // cwg2285: 4
   void test() {
     using T = int[1];
     auto [a] = T{a};
-    // since-cxx17-error@-1 {{binding 'a' cannot appear in the initializer of its own decomposition declaration}}
+    // since-cxx17-error@-1 {{binding 'a' cannot appear in the initializer of its own structured binding declaration}}
   }
 #endif
 } // namespace cwg2285

clang/test/CXX/drs/cwg23xx.cpp

@@ -440,7 +440,7 @@ template <> struct tuple_size<cwg2386::Bad2> {
 namespace cwg2386 {
 void no_value() { auto [x, y] = Bad1(); }
 void wrong_value() { auto [x, y] = Bad2(); }
-// since-cxx17-error@-1 {{type 'Bad2' decomposes into 42 elements, but only 2 names were provided}}
+// since-cxx17-error@-1 {{type 'Bad2' binds to 42 elements, but only 2 names were provided}}
 #endif
 } // namespace cwg2386
 

clang/test/CXX/drs/cwg26xx.cpp

@@ -183,17 +183,17 @@ T get_T();
 
 void use() {
   UnaryC auto [a, b] = get_S();
-  // since-cxx20-error@-1 {{decomposition declaration cannot be declared with constrained 'auto'}}
+  // since-cxx20-error@-1 {{structured binding declaration cannot be declared with constrained 'auto'}}
   BinaryC<int> auto [c, d] = get_S();
-  // since-cxx20-error@-1 {{decomposition declaration cannot be declared with constrained 'auto'}}
+  // since-cxx20-error@-1 {{structured binding declaration cannot be declared with constrained 'auto'}}
 }
 
 template<typename T>
 void TemplUse() {
   UnaryC auto [a, b] = get_T<T>();
-  // since-cxx20-error@-1 {{decomposition declaration cannot be declared with constrained 'auto'}}
+  // since-cxx20-error@-1 {{structured binding declaration cannot be declared with constrained 'auto'}}
   BinaryC<T> auto [c, d] = get_T<T>();
-  // since-cxx20-error@-1 {{decomposition declaration cannot be declared with constrained 'auto'}}
+  // since-cxx20-error@-1 {{structured binding declaration cannot be declared with constrained 'auto'}}
 }
 #endif
 } // namespace cwg2635

clang/test/CXX/stmt.stmt/stmt.iter/stmt.ranged/p1.cpp

@@ -75,7 +75,7 @@ namespace X {
   void test_D() {
 #if __cplusplus >= 201703L
     for (extern auto [x, y] : D()) {
-    } // expected-error@-1 {{decomposition declaration cannot be declared 'extern'}}
+    } // expected-error@-1 {{structured binding declaration cannot be declared 'extern'}}
       // expected-error@-2 {{loop variable '[x, y]' may not be declared 'extern'}}
 #endif
   }