Move code from parser to diagnostics

src/libsyntax/parse/diagnostics.rs

@@ -1,7 +1,6 @@
-use crate::ast;
 use crate::ast::{
-    BlockCheckMode, BinOpKind, Expr, ExprKind, Item, ItemKind, Pat, PatKind, PathSegment, QSelf,
+    self, Arg, BinOpKind, BindingMode, BlockCheckMode, Expr, ExprKind, Ident, Item, ItemKind,
-    Ty, TyKind, VariantData, Ident,
+    Mutability, Pat, PatKind, PathSegment, QSelf, Ty, TyKind, VariantData,
 };
 use crate::parse::{SeqSep, token, PResult, Parser};
 use crate::parse::parser::{BlockMode, PathStyle, SemiColonMode, TokenType, TokenExpectType};
@@ -12,9 +11,25 @@ use crate::symbol::{kw, sym};
 use crate::ThinVec;
 use crate::util::parser::AssocOp;
 use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
+use rustc_data_structures::fx::FxHashSet;
 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
 use log::{debug, trace};
 
+/// Creates a placeholder argument.
+crate fn dummy_arg(ident: Ident) -> Arg {
+    let pat = P(Pat {
+        id: ast::DUMMY_NODE_ID,
+        node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
+        span: ident.span,
+    });
+    let ty = Ty {
+        node: TyKind::Err,
+        span: ident.span,
+        id: ast::DUMMY_NODE_ID
+    };
+    Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal }
+}
+
 pub enum Error {
     FileNotFoundForModule {
         mod_name: String,
@@ -1217,4 +1232,24 @@ impl<'a> Parser<'a> {
         err.span_label(span, "expected expression");
         err
     }
+
+    /// Replace duplicated recovered arguments with `_` pattern to avoid unecessary errors.
+    crate fn deduplicate_recovered_arg_names(&self, fn_inputs: &mut Vec<Arg>) {
+        let mut seen_inputs = FxHashSet::default();
+        for input in fn_inputs.iter_mut() {
+            let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) = (
+                &input.pat.node, &input.ty.node,
+            ) {
+                Some(*ident)
+            } else {
+                None
+            };
+            if let Some(ident) = opt_ident {
+                if seen_inputs.contains(&ident) {
+                    input.pat.node = PatKind::Wild;
+                }
+                seen_inputs.insert(ident);
+            }
+        }
+    }
 }

src/libsyntax/parse/parser.rs

@@ -47,11 +47,10 @@ use crate::parse::PResult;
 use crate::ThinVec;
 use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
 use crate::symbol::{kw, sym, Symbol};
-use crate::parse::diagnostics::Error;
+use crate::parse::diagnostics::{Error, dummy_arg};
 
 use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
 use rustc_target::spec::abi::{self, Abi};
-use rustc_data_structures::fx::FxHashSet;
 use syntax_pos::{Span, BytePos, DUMMY_SP, FileName, hygiene::CompilerDesugaringKind};
 use log::debug;
 
@@ -452,21 +451,6 @@ impl From<P<Expr>> for LhsExpr {
     }
 }
 
-/// Creates a placeholder argument.
-fn dummy_arg(ident: Ident) -> Arg {
-    let pat = P(Pat {
-        id: ast::DUMMY_NODE_ID,
-        node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
-        span: ident.span,
-    });
-    let ty = Ty {
-        node: TyKind::Err,
-        span: ident.span,
-        id: ast::DUMMY_NODE_ID
-    };
-    Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal }
-}
-
 #[derive(Copy, Clone, Debug)]
 crate enum TokenExpectType {
     Expect,
@@ -5617,22 +5601,7 @@ impl<'a> Parser<'a> {
             self.expect(&token::CloseDelim(token::Paren))?;
         }
         // Replace duplicated recovered arguments with `_` pattern to avoid unecessary errors.
-        let mut seen_inputs = FxHashSet::default();
+        self.deduplicate_recovered_arg_names(&mut fn_inputs);
-        for input in fn_inputs.iter_mut() {
-            let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) = (
-                &input.pat.node, &input.ty,
-            ) {
-                Some(*ident)
-            } else {
-                None
-            };
-            if let Some(ident) = opt_ident {
-                if seen_inputs.contains(&ident) {
-                    input.pat.node = PatKind::Wild;
-                }
-                seen_inputs.insert(ident);
-            }
-        }
 
         Ok(P(FnDecl {
             inputs: fn_inputs,