Rollup merge of #141670 - chenyukang:yukang-fix-ice-from-contracts, r=nnethercote

Fix ICE in tokenstream with contracts from parser recovery

Fixes rust-lang/rust#140683

After two times of parsing error, the `recover_stmt_` constructs an error ast, then when we expand macors, the invalid tokenstream triggered ICE because of mismatched delims.

Expected `{` and get other tokens is an obvious error message, too much effort on recovery may introduce noise.

r? ```@nnethercote```

compiler/rustc_parse/src/parser/stmt.rs

@@ -515,8 +515,8 @@ impl<'a> Parser<'a> {
     fn error_block_no_opening_brace_msg(&mut self, msg: Cow<'static, str>) -> Diag<'a> {
         let prev = self.prev_token.span;
         let sp = self.token.span;
-        let mut e = self.dcx().struct_span_err(sp, msg);
-        self.label_expected_raw_ref(&mut e);
+        let mut err = self.dcx().struct_span_err(sp, msg);
+        self.label_expected_raw_ref(&mut err);
 
         let do_not_suggest_help = self.token.is_keyword(kw::In)
             || self.token == token::Colon
@@ -558,20 +558,19 @@ impl<'a> Parser<'a> {
                     stmt.span
                 };
                 self.suggest_fixes_misparsed_for_loop_head(
-                    &mut e,
+                    &mut err,
                     prev.between(sp),
                     stmt_span,
                     &stmt.kind,
                 );
             }
             Err(e) => {
-                self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
-                e.cancel();
+                e.delay_as_bug();
             }
             _ => {}
         }
-        e.span_label(sp, "expected `{`");
-        e
+        err.span_label(sp, "expected `{`");
+        err
     }
 
     fn suggest_fixes_misparsed_for_loop_head(

tests/crashes/140683.rs

@@ -1,5 +0,0 @@
-//@ known-bug: #140683
-impl T {
-#[core::contracts::ensures]
-  fn b() { (loop) }
-}

tests/ui/macros/ice-in-tokenstream-for-contracts-issue-140683.rs

@@ -0,0 +1,13 @@
+#![feature(contracts)]
+#![allow(incomplete_features)]
+
+struct T;
+
+impl T {
+    #[core::contracts::ensures] //~ ERROR expected a `Fn(&_)` closure, found `()`
+    fn b() {(loop)}
+    //~^ ERROR expected `{`, found `)`
+    //~| ERROR expected `{`, found `)`
+}
+
+fn main() {}

tests/ui/macros/ice-in-tokenstream-for-contracts-issue-140683.stderr

@@ -0,0 +1,34 @@
+error: expected `{`, found `)`
+  --> $DIR/ice-in-tokenstream-for-contracts-issue-140683.rs:8:18
+   |
+LL |     fn b() {(loop)}
+   |              ----^ expected `{`
+   |              |
+   |              while parsing this `loop` expression
+
+error: expected `{`, found `)`
+  --> $DIR/ice-in-tokenstream-for-contracts-issue-140683.rs:8:18
+   |
+LL |     fn b() {(loop)}
+   |              ----^ expected `{`
+   |              |
+   |              while parsing this `loop` expression
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0277]: expected a `Fn(&_)` closure, found `()`
+  --> $DIR/ice-in-tokenstream-for-contracts-issue-140683.rs:7:5
+   |
+LL |     #[core::contracts::ensures]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     expected an `Fn(&_)` closure, found `()`
+   |     required by a bound introduced by this call
+   |
+   = help: the trait `for<'a> Fn(&'a _)` is not implemented for `()`
+note: required by a bound in `build_check_ensures`
+  --> $SRC_DIR/core/src/contracts.rs:LL:COL
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/macros/no-close-delim-issue-139248.rs

@@ -2,9 +2,8 @@
 
 macro_rules! m {
     (static a : () = $e:expr) => {
-        static a : () = $e;
-        //~^ ERROR macro expansion ends with an incomplete expression: expected expression
-    }
+        static a: () = $e;
+    };
 }
 
 m! { static a : () = (if b) }

tests/ui/macros/no-close-delim-issue-139248.stderr

@@ -1,33 +1,27 @@
 error: expected `{`, found `)`
-  --> $DIR/no-close-delim-issue-139248.rs:10:27
+  --> $DIR/no-close-delim-issue-139248.rs:9:27
    |
 LL | m! { static a : () = (if b) }
    |                           ^ expected `{`
    |
 note: the `if` expression is missing a block after this condition
-  --> $DIR/no-close-delim-issue-139248.rs:10:26
+  --> $DIR/no-close-delim-issue-139248.rs:9:26
    |
 LL | m! { static a : () = (if b) }
    |                          ^
 
 error: expected `{`, found `)`
-  --> $DIR/no-close-delim-issue-139248.rs:10:27
+  --> $DIR/no-close-delim-issue-139248.rs:9:27
    |
 LL | m! { static a : () = (if b) }
    |                           ^ expected `{`
    |
 note: the `if` expression is missing a block after this condition
-  --> $DIR/no-close-delim-issue-139248.rs:10:26
+  --> $DIR/no-close-delim-issue-139248.rs:9:26
    |
 LL | m! { static a : () = (if b) }
    |                          ^
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: macro expansion ends with an incomplete expression: expected expression
-  --> $DIR/no-close-delim-issue-139248.rs:5:28
-   |
-LL |         static a : () = $e;
-   |                            ^ expected expression
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors