Make unexpected always "return" PResult<()> & add unexpected_any

This prevents breakage when `?` no longer skews inference.

compiler/rustc_builtin_macros/src/asm.rs

@@ -189,7 +189,7 @@ pub fn parse_asm_args<'a>(
             args.templates.push(template);
             continue;
         } else {
-            return p.unexpected();
+            p.unexpected_any()?
         };
 
         allow_templates = false;

compiler/rustc_builtin_macros/src/assert.rs

@@ -151,7 +151,7 @@ fn parse_assert<'a>(cx: &mut ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PRes
         };
 
     if parser.token != token::Eof {
-        return parser.unexpected();
+        parser.unexpected()?;
     }
 
     Ok(Assert { cond_expr, custom_message })

compiler/rustc_parse/src/parser/attr.rs

@@ -380,12 +380,12 @@ impl<'a> Parser<'a> {
         };
 
         if let Some(item) = nt_meta {
-            return match item.meta(item.path.span) {
+            match item.meta(item.path.span) {
                 Some(meta) => {
                     self.bump();
-                    Ok(meta)
+                    return Ok(meta);
                 }
-                None => self.unexpected(),
+                None => self.unexpected()?,
             };
         }
 

compiler/rustc_parse/src/parser/generics.rs

@@ -481,7 +481,7 @@ impl<'a> Parser<'a> {
             }))
         } else {
             self.maybe_recover_bounds_doubled_colon(&ty)?;
-            self.unexpected()
+            self.unexpected_any()
         }
     }
 

compiler/rustc_parse/src/parser/item.rs

@@ -1514,7 +1514,7 @@ impl<'a> Parser<'a> {
                 let ident = this.parse_field_ident("enum", vlo)?;
 
                 if this.token == token::Not {
-                    if let Err(err) = this.unexpected::<()>() {
+                    if let Err(err) = this.unexpected() {
                         err.with_note(fluent::parse_macro_expands_to_enum_variant).emit();
                     }
 
@@ -1937,7 +1937,7 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, FieldDef> {
         let name = self.parse_field_ident(adt_ty, lo)?;
         if self.token.kind == token::Not {
-            if let Err(mut err) = self.unexpected::<FieldDef>() {
+            if let Err(mut err) = self.unexpected() {
                 // Encounter the macro invocation
                 err.subdiagnostic(self.dcx(), MacroExpandsToAdtField { adt_ty });
                 return Err(err);
@@ -2067,7 +2067,7 @@ impl<'a> Parser<'a> {
             let params = self.parse_token_tree(); // `MacParams`
             let pspan = params.span();
             if !self.check(&token::OpenDelim(Delimiter::Brace)) {
-                return self.unexpected();
+                self.unexpected()?;
             }
             let body = self.parse_token_tree(); // `MacBody`
             // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
@@ -2077,7 +2077,7 @@ impl<'a> Parser<'a> {
             let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
             P(DelimArgs { dspan, delim: Delimiter::Brace, tokens })
         } else {
-            return self.unexpected();
+            self.unexpected_any()?
         };
 
         self.psess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_token.span));
@@ -2692,7 +2692,7 @@ impl<'a> Parser<'a> {
                 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
                 let (pat, colon) = this.parse_fn_param_pat_colon()?;
                 if !colon {
-                    let mut err = this.unexpected::<()>().unwrap_err();
+                    let mut err = this.unexpected().unwrap_err();
                     return if let Some(ident) =
                         this.parameter_without_type(&mut err, pat, is_name_required, first_param)
                     {
@@ -2716,7 +2716,7 @@ impl<'a> Parser<'a> {
                 {
                     // This wasn't actually a type, but a pattern looking like a type,
                     // so we are going to rollback and re-parse for recovery.
-                    ty = this.unexpected();
+                    ty = this.unexpected_any();
                 }
                 match ty {
                     Ok(ty) => {

compiler/rustc_parse/src/parser/mod.rs

@@ -465,7 +465,9 @@ impl<'a> Parser<'a> {
         matches!(self.recovery, Recovery::Allowed)
     }
 
-    pub fn unexpected<T>(&mut self) -> PResult<'a, T> {
+    /// Version of [`unexpected`](Parser::unexpected) that "returns" any type in the `Ok`
+    /// (both those functions never return "Ok", and so can lie like that in the type).
+    pub fn unexpected_any<T>(&mut self) -> PResult<'a, T> {
         match self.expect_one_of(&[], &[]) {
             Err(e) => Err(e),
             // We can get `Ok(true)` from `recover_closing_delimiter`
@@ -474,6 +476,10 @@ impl<'a> Parser<'a> {
         }
     }
 
+    pub fn unexpected(&mut self) -> PResult<'a, ()> {
+        self.unexpected_any()
+    }
+
     /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
     pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, Recovered> {
         if self.expected_tokens.is_empty() {
@@ -1278,7 +1284,11 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_delim_args(&mut self) -> PResult<'a, P<DelimArgs>> {
-        if let Some(args) = self.parse_delim_args_inner() { Ok(P(args)) } else { self.unexpected() }
+        if let Some(args) = self.parse_delim_args_inner() {
+            Ok(P(args))
+        } else {
+            self.unexpected_any()
+        }
     }
 
     fn parse_attr_args(&mut self) -> PResult<'a, AttrArgs> {

compiler/rustc_parse/src/parser/path.rs

@@ -660,7 +660,7 @@ impl<'a> Parser<'a> {
                     // Add `>` to the list of expected tokens.
                     self.check(&token::Gt);
                     // Handle `,` to `;` substitution
-                    let mut err = self.unexpected::<()>().unwrap_err();
+                    let mut err = self.unexpected().unwrap_err();
                     self.bump();
                     err.span_suggestion_verbose(
                         self.prev_token.span.until(self.token.span),