move diagnostics.rs into parser/

src/libsyntax/parse/parser/expr.rs

@@ -1,6 +1,7 @@
 use super::{Parser, PResult, Restrictions, PrevTokenKind, TokenType, PathStyle, BlockMode};
 use super::{SemiColonMode, SeqSep, TokenExpectType};
 use super::pat::{GateOr, PARAM_EXPECTED};
+use super::diagnostics::Error;
 
 use crate::parse::literal::LitError;
 
@@ -12,7 +13,6 @@ use crate::ast::{
 use crate::maybe_recover_from_interpolated_ty_qpath;
 use crate::parse::classify;
 use crate::parse::token::{self, Token, TokenKind};
-use crate::parse::diagnostics::Error;
 use crate::print::pprust;
 use crate::ptr::P;
 use crate::source_map::{self, Span};