Rollup merge of #43822 - topecongiro:missing-span-let, r=petrochenkov

Include 'let' keyword to the span for ast::Local

Currently the span for `ast::Local` does not the include the `let` keyword. This PR fixes it.

Author: GuillaumeGomez

src/libsyntax/parse/parser.rs

@@ -3587,7 +3587,7 @@ impl<'a> Parser<'a> {
 
     /// Parse a local variable declaration
     fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
-        let lo = self.span;
+        let lo = self.prev_span;
         let pat = self.parse_pat()?;
 
         let ty = if self.eat(&token::Colon) {