[clang] [clang-tools-extra] [clang-tidy] Add new check `modernize-use-designated-initializers` (PR #80541)

[Danny Mösch via cfe-commits]

================
@@ -0,0 +1,115 @@
+// RUN: %check_clang_tidy -std=c++17 %s modernize-use-designated-initializers %t
+// RUN: %check_clang_tidy -check-suffixes=,SINGLE-ELEMENT -std=c++17 %s modernize-use-designated-initializers %t \
+// RUN:     -- -config="{CheckOptions: [{key: modernize-use-designated-initializers.IgnoreSingleElementAggregates, value: false}]}" \
+// RUN:     --
+// RUN: %check_clang_tidy -check-suffixes=POD -std=c++17 %s modernize-use-designated-initializers %t \
+// RUN:     -- -config="{CheckOptions: [{key: modernize-use-designated-initializers.RestrictToPODTypes, value: true}]}" \
+// RUN:     --
+
+struct S1 {};
+
+S1 s11{};
+S1 s12 = {};
+S1 s13();
+S1 s14;
+
+struct S2 { int i, j; };
+
+S2 s21{.i=1, .j =2};
+
+S2 s22 = {1, 2};
+// CHECK-MESSAGES: :[[@LINE-1]]:10: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-2]]:10: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-FIXES: S2 s22 = {.i=1, .j=2};
+
+S2 s23{1};
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-2]]:7: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-FIXES: S2 s23{.i=1};
+
+S2 s24{.i = 1};
+
+S2 s25 = {.i=1, 2};
+// CHECK-MESSAGES: :[[@LINE-1]]:17: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-2]]:17: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-FIXES: S2 s25 = {.i=1, .j=2};
+
+class S3 {
+  public:
+    S2 s2;
+    double d;
+};
+
+S3 s31 = {.s2 = 1, 2, 3.1};
+// CHECK-MESSAGES: :[[@LINE-1]]:20: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-MESSAGES: :[[@LINE-2]]:23: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-3]]:20: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-4]]:23: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-FIXES: S3 s31 = {.s2 = 1, .s2.j=2, .d=3.1};
+
+S3 s32 = {{.i = 1, 2}};
+// CHECK-MESSAGES: :[[@LINE-1]]:10: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-MESSAGES: :[[@LINE-2]]:20: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-3]]:10: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-4]]:20: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-FIXES: S3 s32 = {.s2={.i = 1, 2}};
+
+struct S4 {
+    double d;
+    private: static int i;
+};
+
+S4 s41 {2.2};
+// CHECK-MESSAGES-SINGLE-ELEMENT: :[[@LINE-1]]:8: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-FIXES-SINGLE-ELEMENT: S4 s41 {.d=2.2};
+
+S4 s42 = {{}};
+// CHECK-MESSAGES-SINGLE-ELEMENT: :[[@LINE-1]]:10: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-FIXES-SINGLE-ELEMENT: S4 s42 = {.d={}};
+
+template<typename S> S template1() { return {10, 11}; }
+
+S2 s26 = template1<S2>();
+
+template<typename S> S template2() { return {}; }
+
+S2 s27 = template2<S2>();
+
+struct S5: S2 { int x, y; };
+
+S5 s51 {1, 2, .x = 3, .y = 4};
+
+struct S6 {
+    int i;
+    struct { int j; } s;
+};
+
+S6 s61 {1, 2};
+
+struct S7 {
+    union {
+        int k;
+        double d;
+    } u;
+};
+
+S7 s71 {1};
+
+struct S8: S7 { int i; };
+
+S8 s81{1, 2};
+
+struct S9 {
+    int i, j;
+    S9 &operator=(S9);
+};
+
+S9 s91{1, 2};
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use designated initializer list [modernize-use-designated-initializers]
+// CHECK-FIXES: S9 s91{.i=1, .j=2};
+
+struct S10 { int i = 1, j = 2; };
+
+S10 s101 {1, .j=2};
+// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: use designated init expression [modernize-use-designated-initializers]
+// CHECK-FIXES: S10 s101 {.i=1, .j=2};
----------------
SimplyDanny wrote:

Good catch! Fixed it.

https://github.com/llvm/llvm-project/pull/80541