Apply Recovery::Forbidden when reparsing pasted macro fragments.

Fixes #137874.

Removes `tests/crashes/137874.rs`; the new test is simpler (defines its
own macro) but tests the same thing.

The changes to the output of `tests/ui/associated-consts/issue-93835.rs`
partly undo the changes seen when `NtTy` was removed in #133436, which
is good.

Author: nnethercote

Diff for: compiler/rustc_parse/src/parser/mod.rs

@@ -512,6 +512,14 @@ impl<'a> Parser<'a> {
         self
     }
 
+    #[inline]
+    fn with_recovery<T>(&mut self, recovery: Recovery, f: impl FnOnce(&mut Self) -> T) -> T {
+        let old = mem::replace(&mut self.recovery, recovery);
+        let res = f(self);
+        self.recovery = old;
+        res
+    }
+
     /// Whether the parser is allowed to recover from broken code.
     ///
     /// If this returns false, recovering broken code into valid code (especially if this recovery does lookahead)
@@ -770,7 +778,14 @@ impl<'a> Parser<'a> {
             && match_mv_kind(mv_kind)
         {
             self.bump();
-            let res = f(self).expect("failed to reparse {mv_kind:?}");
+
+            // Recovery is disabled when parsing macro arguments, so it must
+            // also be disabled when reparsing pasted macro arguments,
+            // otherwise we get inconsistent results (e.g. #137874).
+            let res = self.with_recovery(Recovery::Forbidden, |this| {
+                f(this).expect("failed to reparse {mv_kind:?}")
+            });
+
             if let token::CloseDelim(delim) = self.token.kind
                 && let Delimiter::Invisible(InvisibleOrigin::MetaVar(mv_kind)) = delim
                 && match_mv_kind(mv_kind)

Diff for: tests/crashes/137874.rs

@@ -3,11 +3,10 @@
 fn e() {
     type_ascribe!(p, a<p:p<e=6>>);
     //~^ ERROR cannot find type `a` in this scope
-    //~| ERROR path separator must be a double colon
     //~| ERROR cannot find value
     //~| ERROR associated const equality
+    //~| ERROR cannot find trait `p` in this scope
     //~| ERROR associated const equality
-    //~| ERROR failed to resolve: use of unresolved module or unlinked crate `p`
 }
 
 fn main() {}

Diff for: tests/ui/associated-consts/issue-93835.rs

@@ -1,15 +1,3 @@
-error: path separator must be a double colon
-  --> $DIR/issue-93835.rs:4:25
-   |
-LL |     type_ascribe!(p, a<p:p<e=6>>);
-   |                         ^
-   |
-   = note: if you meant to annotate an expression with a type, the type ascription syntax has been removed, see issue #101728 <https://github.com/rust-lang/rust/issues/101728>
-help: use a double colon instead
-   |
-LL |     type_ascribe!(p, a<p::p<e=6>>);
-   |                          +
-
 error[E0425]: cannot find value `p` in this scope
   --> $DIR/issue-93835.rs:4:19
    |
@@ -22,6 +10,12 @@ error[E0412]: cannot find type `a` in this scope
 LL |     type_ascribe!(p, a<p:p<e=6>>);
    |                      ^ not found in this scope
 
+error[E0405]: cannot find trait `p` in this scope
+  --> $DIR/issue-93835.rs:4:26
+   |
+LL |     type_ascribe!(p, a<p:p<e=6>>);
+   |                          ^ not found in this scope
+
 error[E0658]: associated const equality is incomplete
   --> $DIR/issue-93835.rs:4:28
    |
@@ -43,15 +37,7 @@ LL |     type_ascribe!(p, a<p:p<e=6>>);
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0433]: failed to resolve: use of unresolved module or unlinked crate `p`
-  --> $DIR/issue-93835.rs:4:24
-   |
-LL |     type_ascribe!(p, a<p:p<e=6>>);
-   |                        ^ use of unresolved module or unlinked crate `p`
-   |
-   = help: you might be missing a crate named `p`
-
-error: aborting due to 6 previous errors
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0412, E0425, E0433, E0658.
-For more information about an error, try `rustc --explain E0412`.
+Some errors have detailed explanations: E0405, E0412, E0425, E0658.
+For more information about an error, try `rustc --explain E0405`.

Diff for: tests/ui/associated-consts/issue-93835.stderr

@@ -0,0 +1,12 @@
+// This originally crashed because `Recovery::Forbidden` wasn't being applied
+// when fragments pasted by declarative macros were reparsed.
+
+macro_rules! m {
+    ($p:pat) => {
+        if let $p = 0 {}
+    }
+}
+
+fn main() {
+    m!(0X0); //~ ERROR invalid base prefix for number literal
+}

Diff for: tests/ui/macros/failed-to-reparse-issue-137874.rs

@@ -0,0 +1,10 @@
+error: invalid base prefix for number literal
+  --> $DIR/failed-to-reparse-issue-137874.rs:11:8
+   |
+LL |     m!(0X0);
+   |        ^^^ help: try making the prefix lowercase (notice the capitalization): `0x0`
+   |
+   = note: base prefixes (`0xff`, `0b1010`, `0o755`) are lowercase
+
+error: aborting due to 1 previous error
+