Rollup merge of #136274 - compiler-errors:sized-wf, r=lcnr

Check Sizedness of return type in WF

Still need to clean this up a bit. This should fix https://github.com/rust-lang/trait-system-refactor-initiative/issues/150.

r? lcnr

tests/rustdoc-ui/custom_code_classes_in_docs-warning3.rs

@@ -2,9 +2,12 @@
 // feature.
 
 #![deny(warnings)]
-#![feature(no_core)]
+#![feature(no_core, lang_items)]
 #![no_core]
 
+#[lang = "sized"]
+trait Sized {}
+
 /// ```{class="}
 /// main;
 /// ```

tests/rustdoc-ui/custom_code_classes_in_docs-warning3.stderr

@@ -1,5 +1,5 @@
 error: unclosed quote string `"`
-  --> $DIR/custom_code_classes_in_docs-warning3.rs:8:1
+  --> $DIR/custom_code_classes_in_docs-warning3.rs:11:1
    |
 LL | / /// ```{class="}
 LL | | /// main;
@@ -17,7 +17,7 @@ LL | #![deny(warnings)]
    = note: `#[deny(rustdoc::invalid_codeblock_attributes)]` implied by `#[deny(warnings)]`
 
 error: unclosed quote string `"`
-  --> $DIR/custom_code_classes_in_docs-warning3.rs:8:1
+  --> $DIR/custom_code_classes_in_docs-warning3.rs:11:1
    |
 LL | / /// ```{class="}
 LL | | /// main;