[clangd] Drop explicit specifier on define out-of-line

[kadircet]

Summary

Explicit specifier can only be mentioned on the in-line declaration of a
constructor, so don't carry it over to the definition.

clang-tools-extra/clangd/refactor/tweaks/DefineOutline.cpp

getFunctionSourceCode(const FunctionDecl *FD, llvm::StringRef TargetNamespace,
   };
 
   if (const auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
     if (MD->isVirtualAsWritten())
       DelKeyword(tok::kw_virtual, {FD->getBeginLoc(), FD->getLocation()});
     if (MD->isStatic())
       DelKeyword(tok::kw_static, {FD->getBeginLoc(), FD->getLocation()});
   }
+  if (const auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
+    if (CD->isExplicit())
+      DelKeyword(tok::kw_explicit, {FD->getBeginLoc(), FD->getLocation()});
+  }
 
   if (Errors)
     return std::move(Errors);
   return getFunctionSourceAfterReplacements(FD, DeclarationCleanups);
 }
 
 struct InsertionPoint {
   std::string EnclosingNamespace;

clang-tools-extra/clangd/unittests/tweaks/DefineOutlineTests.cpp

llvm::StringRef ExpectedSource;
               static static void fo^o() {}
             };)cpp",
           R"cpp(
             struct A {
               static static void foo() ;
             };)cpp",
           "  void A::foo() {}\n",
       },
+      {
+          R"cpp(
+            struct Foo {
+              explicit Fo^o(int) {}
+            };)cpp",
+          R"cpp(
+            struct Foo {
+              explicit Foo(int) ;
+            };)cpp",
+          " Foo::Foo(int) {}\n",
+      },
+      {
+          R"cpp(
+            struct Foo {
+              explicit explicit Fo^o(int) {}
+            };)cpp",
+          R"cpp(
+            struct Foo {
+              explicit explicit Foo(int) ;
+            };)cpp",
+          "  Foo::Foo(int) {}\n",
+      },
   };
   for (const auto &Case : Cases) {
     SCOPED_TRACE(Case.Test);
     EXPECT_EQ(apply(Case.Test, &EditedFiles), Case.ExpectedHeader);
     EXPECT_THAT(EditedFiles, testing::ElementsAre(FileWithContents(
                                  testPath("Test.cpp"), Case.ExpectedSource)));
   }
 }