Auto merge of #46732 - estebank:silence-recovered-blocks, r=petrochenkov

Do not emit type errors on recovered blocks

When a parse error occurs on a block, the parser will recover and create
a block with the statements collected until that point. Now a flag
stating that a recovery has been performed in this block is propagated
so that the type checker knows that the type of the block (which will be
identified as `()`) shouldn't be checked against the expectation to
reduce the amount of irrelevant diagnostic errors shown to the user.

Fix #44579.

src/libsyntax/ast.rs

@@ -493,6 +493,7 @@ pub struct Block {
     /// Distinguishes between `unsafe { ... }` and `{ ... }`
     pub rules: BlockCheckMode,
     pub span: Span,
+    pub recovered: bool,
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]