Auto merge of #27613 - GSam:binop, r=nrc
Auto merge of #27613 - GSam:binop, r=nrc

In the case where there are no paren in the AST, the pretty printer doesn't correctly print binary operations where precedence is concerned. Parenthesis may be missing due to some kind of expansion or manipulation of the AST. 

Example:
Pretty printer prints Expr(*, Expr(+, 1, 1), 2) as 1 + 1 * 2, as opposed to (1 + 1) * 2

r? @nrc

GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust