Fix clippy lint empty_docs (rustwasm#3946)

* Do not include docstring if empty

Closes rustwasm#3945

* Move changelog entry to correct section

CHANGELOG.md

@@ -27,6 +27,9 @@
 * Fix MSRV compilation.
   [#3927](https://github.com/rustwasm/wasm-bindgen/pull/3927)
 
+* Fixed `clippy::empty_docs` lint.
+  [#3946](https://github.com/rustwasm/wasm-bindgen/pull/3946)
+
 --------------------------------------------------------------------------------
 
 ## [0.2.92](https://github.com/rustwasm/wasm-bindgen/compare/0.2.91...0.2.92)

crates/backend/src/codegen.rs

@@ -815,10 +815,18 @@ impl ToTokens for ast::ImportType {
 
         let no_deref = self.no_deref;
 
+        let doc = if doc_comment.is_empty() {
+            quote! {}
+        } else {
+            quote! {
+                #[doc = #doc_comment]
+            }
+        };
+
         (quote! {
             #[automatically_derived]
             #(#attrs)*
-            #[doc = #doc_comment]
+            #doc
             #[repr(transparent)]
             #vis struct #rust_name {
                 obj: #internal_obj
@@ -1294,7 +1302,12 @@ impl TryToTokens for ast::ImportFunction {
         let abi_arguments = &abi_arguments[..];
         let abi_argument_names = &abi_argument_names[..];
 
-        let doc_comment = &self.doc_comment;
+        let doc = if self.doc_comment.is_empty() {
+            quote! {}
+        } else {
+            let doc_comment = &self.doc_comment;
+            quote! { #[doc = #doc_comment] }
+        };
         let me = if is_method {
             quote! { &self, }
         } else {
@@ -1343,7 +1356,7 @@ impl TryToTokens for ast::ImportFunction {
             #[allow(nonstandard_style)]
             #[allow(clippy::all, clippy::nursery, clippy::pedantic, clippy::restriction)]
             #(#attrs)*
-            #[doc = #doc_comment]
+            #doc
             #vis #maybe_async #maybe_unsafe fn #rust_name(#me #(#arguments),*) #ret {
                 #extern_fn