Auto merge of rust-lang#74963 - JohnTitor:ptn-ice, r=petrochenkov

Fix ICEs with `@ ..` binding

This reverts rust-lang#74557 and introduces an alternative fix while ensuring that rust-lang#74954 is not broken.
The diagnostics are verbose though, it fixes three related issues.
cc rust-lang#74954, rust-lang#74539, and rust-lang#74702

Author: bors

src/librustc_ast_lowering/pat.rs

@@ -112,7 +112,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 // Found a sub-tuple pattern `$binding_mode $ident @ ..`.
                 // This is not allowed as a sub-tuple pattern
                 PatKind::Ident(ref _bm, ident, Some(ref sub)) if sub.is_rest() => {
-                    rest = Some((idx, pat.span));
                     let sp = pat.span;
                     self.diagnostic()
                         .struct_span_err(
@@ -128,7 +127,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             Applicability::MaybeIncorrect,
                         )
                         .emit();
-                    break;
                 }
                 _ => {}
             }

src/librustc_resolve/late.rs

@@ -1510,30 +1510,18 @@ impl<'a, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         pat_src: PatternSource,
         bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
     ) {
-        let is_tuple_struct_pat = matches!(pat.kind, PatKind::TupleStruct(_, _));
-
         // Visit all direct subpatterns of this pattern.
         pat.walk(&mut |pat| {
             debug!("resolve_pattern pat={:?} node={:?}", pat, pat.kind);
             match pat.kind {
                 PatKind::Ident(bmode, ident, ref sub) => {
-                    if is_tuple_struct_pat && sub.as_ref().filter(|p| p.is_rest()).is_some() {
-                        // In tuple struct patterns ignore the invalid `ident @ ...`.
-                        // It will be handled as an error by the AST lowering.
-                        self.r
-                            .session
-                            .delay_span_bug(ident.span, "ident in tuple pattern is invalid");
-                    } else {
-                        // First try to resolve the identifier as some existing entity,
-                        // then fall back to a fresh binding.
-                        let has_sub = sub.is_some();
-                        let res = self
-                            .try_resolve_as_non_binding(pat_src, pat, bmode, ident, has_sub)
-                            .unwrap_or_else(|| {
-                                self.fresh_binding(ident, pat.id, pat_src, bindings)
-                            });
-                        self.r.record_partial_res(pat.id, PartialRes::new(res));
-                    }
+                    // First try to resolve the identifier as some existing entity,
+                    // then fall back to a fresh binding.
+                    let has_sub = sub.is_some();
+                    let res = self
+                        .try_resolve_as_non_binding(pat_src, pat, bmode, ident, has_sub)
+                        .unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings));
+                    self.r.record_partial_res(pat.id, PartialRes::new(res));
                 }
                 PatKind::TupleStruct(ref path, ..) => {
                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct(pat.span));

src/test/ui/issues/issue-72574-1.rs

@@ -6,3 +6,5 @@ fn main() {
     }
 }
 //~^^^^ ERROR `_x @` is not allowed in a tuple
+//~| ERROR: `..` patterns are not allowed here
+//~| ERROR: mismatched types

src/test/ui/issues/issue-72574-1.stderr

@@ -10,5 +10,25 @@ help: if you don't need to use the contents of _x, discard the tuple's remaining
 LL |         (_a, ..) => {}
    |              ^^
 
-error: aborting due to previous error
+error: `..` patterns are not allowed here
+  --> $DIR/issue-72574-1.rs:4:19
+   |
+LL |         (_a, _x @ ..) => {}
+   |                   ^^
+   |
+   = note: only allowed in tuple, tuple struct, and slice patterns
+
+error[E0308]: mismatched types
+  --> $DIR/issue-72574-1.rs:4:9
+   |
+LL |     match x {
+   |           - this expression has type `({integer}, {integer}, {integer})`
+LL |         (_a, _x @ ..) => {}
+   |         ^^^^^^^^^^^^^ expected a tuple with 3 elements, found one with 2 elements
+   |
+   = note: expected tuple `({integer}, {integer}, {integer})`
+              found tuple `(_, _)`
+
+error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/issues/issue-72574-2.rs

@@ -8,3 +8,5 @@ fn main() {
     }
 }
 //~^^^^ ERROR `_x @` is not allowed in a tuple struct
+//~| ERROR: `..` patterns are not allowed here
+//~| ERROR: this pattern has 2 fields, but the corresponding tuple struct has 3 fields

src/test/ui/issues/issue-72574-2.stderr

@@ -10,5 +10,23 @@ help: if you don't need to use the contents of _x, discard the tuple's remaining
 LL |         Binder(_a, ..) => {}
    |                    ^^
 
-error: aborting due to previous error
+error: `..` patterns are not allowed here
+  --> $DIR/issue-72574-2.rs:6:25
+   |
+LL |         Binder(_a, _x @ ..) => {}
+   |                         ^^
+   |
+   = note: only allowed in tuple, tuple struct, and slice patterns
+
+error[E0023]: this pattern has 2 fields, but the corresponding tuple struct has 3 fields
+  --> $DIR/issue-72574-2.rs:6:9
+   |
+LL | struct Binder(i32, i32, i32);
+   | ----------------------------- tuple struct defined here
+...
+LL |         Binder(_a, _x @ ..) => {}
+   |         ^^^^^^^^^^^^^^^^^^^ expected 3 fields, found 2
+
+error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0023`.

src/test/ui/issues/issue-74539.rs

@@ -0,0 +1,15 @@
+enum E {
+    A(u8, u8),
+}
+
+fn main() {
+    let e = E::A(2, 3);
+    match e {
+        E::A(x @ ..) => {
+            //~^ ERROR: `x @` is not allowed in a tuple struct
+            //~| ERROR: `..` patterns are not allowed here
+            //~| ERROR: this pattern has 1 field, but the corresponding tuple variant has 2 fields
+            x
+        }
+    };
+}

src/test/ui/issues/issue-74539.stderr

@@ -0,0 +1,32 @@
+error: `x @` is not allowed in a tuple struct
+  --> $DIR/issue-74539.rs:8:14
+   |
+LL |         E::A(x @ ..) => {
+   |              ^^^^^^ this is only allowed in slice patterns
+   |
+   = help: remove this and bind each tuple field independently
+help: if you don't need to use the contents of x, discard the tuple's remaining fields
+   |
+LL |         E::A(..) => {
+   |              ^^
+
+error: `..` patterns are not allowed here
+  --> $DIR/issue-74539.rs:8:18
+   |
+LL |         E::A(x @ ..) => {
+   |                  ^^
+   |
+   = note: only allowed in tuple, tuple struct, and slice patterns
+
+error[E0023]: this pattern has 1 field, but the corresponding tuple variant has 2 fields
+  --> $DIR/issue-74539.rs:8:9
+   |
+LL |     A(u8, u8),
+   |     --------- tuple variant defined here
+...
+LL |         E::A(x @ ..) => {
+   |         ^^^^^^^^^^^^ expected 2 fields, found 1
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0023`.

src/test/ui/pattern/issue-74539.rs

@@ -0,0 +1,7 @@
+fn main() {
+    let (foo @ ..,) = (0, 0);
+    //~^ ERROR: `foo @` is not allowed in a tuple
+    //~| ERROR: `..` patterns are not allowed here
+    //~| ERROR: mismatched types
+    dbg!(foo);
+}

src/test/ui/pattern/issue-74539.stderr

@@ -0,0 +1,34 @@
+error: `foo @` is not allowed in a tuple
+  --> $DIR/issue-74702.rs:2:10
+   |
+LL |     let (foo @ ..,) = (0, 0);
+   |          ^^^^^^^^ this is only allowed in slice patterns
+   |
+   = help: remove this and bind each tuple field independently
+help: if you don't need to use the contents of foo, discard the tuple's remaining fields
+   |
+LL |     let (..,) = (0, 0);
+   |          ^^
+
+error: `..` patterns are not allowed here
+  --> $DIR/issue-74702.rs:2:16
+   |
+LL |     let (foo @ ..,) = (0, 0);
+   |                ^^
+   |
+   = note: only allowed in tuple, tuple struct, and slice patterns
+
+error[E0308]: mismatched types
+  --> $DIR/issue-74702.rs:2:9
+   |
+LL |     let (foo @ ..,) = (0, 0);
+   |         ^^^^^^^^^^^   ------ this expression has type `({integer}, {integer})`
+   |         |
+   |         expected a tuple with 2 elements, found one with 1 element
+   |
+   = note: expected tuple `({integer}, {integer})`
+              found tuple `(_,)`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/pattern/issue-74702.rs

@@ -0,0 +1,7 @@
+// check-pass
+
+fn main() {
+    if let Some([b'@', filename @ ..]) = Some(b"@abc123") {
+        println!("filename {:?}", filename);
+    }
+}