Further improve diagnostics for expressions in pattern position

compiler/rustc_errors/src/lib.rs

@@ -571,6 +571,8 @@ pub enum StashKey {
     /// Query cycle detected, stashing in favor of a better error.
     Cycle,
     UndeterminedMacroResolution,
+    /// Used by `Parser::maybe_recover_trailing_expr`
+    ExprInPat,
 }
 
 fn default_track_diagnostic<R>(diag: DiagInner, f: &mut dyn FnMut(DiagInner) -> R) -> R {

compiler/rustc_parse/messages.ftl

@@ -803,15 +803,17 @@ parse_unexpected_expr_in_pat =
     expected {$is_bound ->
         [true] a pattern range bound
        *[false] a pattern
-    }, found {$is_method_call ->
-        [true] a method call
-       *[false] an expression
-    }
+    }, found an expression
+
+    .label = arbitrary expressions are not allowed in patterns
+
+parse_unexpected_expr_in_pat_const_sugg = consider extracting the expression into a `const`
+
+parse_unexpected_expr_in_pat_create_guard_sugg = consider moving the expression to a match arm guard
+
+parse_unexpected_expr_in_pat_inline_const_sugg = consider wrapping the expression in an inline `const` (requires `{"#"}![feature(inline_const_pat)]`)
 
-    .label = {$is_method_call ->
-        [true] method calls
-       *[false] arbitrary expressions
-    } are not allowed in patterns
+parse_unexpected_expr_in_pat_update_guard_sugg = consider moving the expression to the match arm guard
 
 parse_unexpected_if_with_if = unexpected `if` in the condition expression
     .suggestion = remove the `if`

compiler/rustc_parse/src/errors.rs

@@ -1,3 +1,5 @@
+// ignore-tidy-filelength
+
 use std::borrow::Cow;
 
 use rustc_ast::token::Token;
@@ -2592,13 +2594,86 @@ pub(crate) struct ExpectedCommaAfterPatternField {
 #[derive(Diagnostic)]
 #[diag(parse_unexpected_expr_in_pat)]
 pub(crate) struct UnexpectedExpressionInPattern {
+    /// The unexpected expr's span.
     #[primary_span]
     #[label]
     pub span: Span,
     /// Was a `RangePatternBound` expected?
     pub is_bound: bool,
-    /// Was the unexpected expression a `MethodCallExpression`?
-    pub is_method_call: bool,
+    /// The unexpected expr's precedence (used in match arm guard suggestions).
+    pub expr_precedence: i8,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum UnexpectedExpressionInPatternSugg {
+    #[multipart_suggestion(
+        parse_unexpected_expr_in_pat_create_guard_sugg,
+        applicability = "maybe-incorrect"
+    )]
+    CreateGuard {
+        /// Where to put the suggested identifier.
+        #[suggestion_part(code = "{ident}")]
+        ident_span: Span,
+        /// Where to put the match arm.
+        #[suggestion_part(code = " if {ident} == {expr}")]
+        pat_hi: Span,
+        /// The suggested identifier.
+        ident: String,
+        /// The unexpected expression.
+        expr: String,
+    },
+
+    #[multipart_suggestion(
+        parse_unexpected_expr_in_pat_update_guard_sugg,
+        applicability = "maybe-incorrect"
+    )]
+    UpdateGuard {
+        /// Where to put the suggested identifier.
+        #[suggestion_part(code = "{ident}")]
+        ident_span: Span,
+        /// The beginning of the match arm guard's expression (insert a `(` if `Some`).
+        #[suggestion_part(code = "(")]
+        guard_lo: Option<Span>,
+        /// The end of the match arm guard's expression.
+        #[suggestion_part(code = "{guard_hi_paren} && {ident} == {expr}")]
+        guard_hi: Span,
+        /// Either `")"` or `""`.
+        guard_hi_paren: &'static str,
+        /// The suggested identifier.
+        ident: String,
+        /// The unexpected expression.
+        expr: String,
+    },
+
+    #[multipart_suggestion(
+        parse_unexpected_expr_in_pat_const_sugg,
+        applicability = "has-placeholders"
+    )]
+    Const {
+        /// Where to put the extracted constant declaration.
+        #[suggestion_part(code = "{indentation}const {ident}: /* Type */ = {expr};\n")]
+        stmt_lo: Span,
+        /// Where to put the suggested identifier.
+        #[suggestion_part(code = "{ident}")]
+        ident_span: Span,
+        /// The suggested identifier.
+        ident: String,
+        /// The unexpected expression.
+        expr: String,
+        /// The statement's block's indentation.
+        indentation: String,
+    },
+
+    #[multipart_suggestion(
+        parse_unexpected_expr_in_pat_inline_const_sugg,
+        applicability = "maybe-incorrect"
+    )]
+    InlineConst {
+        #[suggestion_part(code = "const {{ ")]
+        start_span: Span,
+        #[suggestion_part(code = " }}")]
+        end_span: Span,
+    },
 }
 
 #[derive(Diagnostic)]

compiler/rustc_parse/src/parser/expr.rs

@@ -41,7 +41,7 @@ use super::{
 use crate::{errors, maybe_recover_from_interpolated_ty_qpath};
 
 #[derive(Debug)]
-enum DestructuredFloat {
+pub(super) enum DestructuredFloat {
     /// 1e2
     Single(Symbol, Span),
     /// 1.
@@ -1041,7 +1041,7 @@ impl<'a> Parser<'a> {
     //  support pushing "future tokens" (would be also helpful to `break_and_eat`), or
     //  we should break everything including floats into more basic proc-macro style
     //  tokens in the lexer (probably preferable).
-    fn break_up_float(&self, float: Symbol, span: Span) -> DestructuredFloat {
+    pub(super) fn break_up_float(&self, float: Symbol, span: Span) -> DestructuredFloat {
         #[derive(Debug)]
         enum FloatComponent {
             IdentLike(String),

compiler/rustc_parse/src/parser/stmt.rs

@@ -29,6 +29,9 @@ use crate::{errors, maybe_whole};
 impl<'a> Parser<'a> {
     /// Parses a statement. This stops just before trailing semicolons on everything but items.
     /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
+    ///
+    /// If `force_collect` is [`ForceCollect::Yes`], forces collection of tokens regardless of
+    /// whether or not we have attributes.
     // Public for rustfmt usage.
     pub(super) fn parse_stmt(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<Stmt>> {
         Ok(self.parse_stmt_without_recovery(false, force_collect).unwrap_or_else(|e| {
@@ -66,7 +69,7 @@ impl<'a> Parser<'a> {
             });
         }
 
-        Ok(Some(if self.token.is_keyword(kw::Let) {
+        let stmt = if self.token.is_keyword(kw::Let) {
             self.collect_tokens(None, attrs, force_collect, |this, attrs| {
                 this.expect_keyword(kw::Let)?;
                 let local = this.parse_local(attrs)?;
@@ -163,7 +166,10 @@ impl<'a> Parser<'a> {
         } else {
             self.error_outer_attrs(attrs);
             return Ok(None);
-        }))
+        };
+
+        self.maybe_augment_stashed_expr_in_pats_with_suggestions(&stmt);
+        Ok(Some(stmt))
     }
 
     fn parse_stmt_path_start(&mut self, lo: Span, attrs: AttrWrapper) -> PResult<'a, Stmt> {

tests/ui/half-open-range-patterns/range_pat_interactions1.stderr

@@ -3,6 +3,17 @@ error: expected a pattern range bound, found an expression
    |
 LL |             0..5+1 => errors_only.push(x),
    |                ^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +         const VAL: /* Type */ = 5+1;
+LL ~         match x as i32 {
+LL ~             0..VAL => errors_only.push(x),
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |             0..const { 5+1 } => errors_only.push(x),
+   |                +++++++     +
 
 error[E0408]: variable `n` is not bound in all patterns
   --> $DIR/range_pat_interactions1.rs:10:25

tests/ui/half-open-range-patterns/range_pat_interactions2.stderr

@@ -1,9 +1,3 @@
-error: expected a pattern range bound, found an expression
-  --> $DIR/range_pat_interactions2.rs:10:18
-   |
-LL |             0..=(5+1) => errors_only.push(x),
-   |                  ^^^ arbitrary expressions are not allowed in patterns
-
 error: range pattern bounds cannot have parentheses
   --> $DIR/range_pat_interactions2.rs:10:17
    |
@@ -16,6 +10,23 @@ LL -             0..=(5+1) => errors_only.push(x),
 LL +             0..=5+1 => errors_only.push(x),
    |
 
+error: expected a pattern range bound, found an expression
+  --> $DIR/range_pat_interactions2.rs:10:18
+   |
+LL |             0..=(5+1) => errors_only.push(x),
+   |                  ^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +         const VAL: /* Type */ = 5+1;
+LL ~         match x as i32 {
+LL ~             0..=(VAL) => errors_only.push(x),
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |             0..=(const { 5+1 }) => errors_only.push(x),
+   |                  +++++++     +
+
 error[E0658]: inline-const in pattern position is experimental
   --> $DIR/range_pat_interactions2.rs:15:20
    |

tests/ui/parser/bad-name.rs

@@ -1,5 +1,6 @@
-//@ error-pattern: expected
-
 fn main() {
   let x.y::<isize>.z foo;
+  //~^ error: field expressions cannot have generic arguments
+  //~| error: expected a pattern, found an expression
+  //~| error: expected one of `(`, `.`, `::`, `:`, `;`, `=`, `?`, `|`, or an operator, found `foo`
 }

tests/ui/parser/bad-name.stderr

@@ -1,8 +1,20 @@
-error: expected one of `:`, `;`, `=`, `@`, or `|`, found `.`
-  --> $DIR/bad-name.rs:4:8
+error: field expressions cannot have generic arguments
+  --> $DIR/bad-name.rs:2:12
    |
 LL |   let x.y::<isize>.z foo;
-   |        ^ expected one of `:`, `;`, `=`, `@`, or `|`
+   |            ^^^^^^^
 
-error: aborting due to 1 previous error
+error: expected a pattern, found an expression
+  --> $DIR/bad-name.rs:2:7
+   |
+LL |   let x.y::<isize>.z foo;
+   |       ^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+
+error: expected one of `(`, `.`, `::`, `:`, `;`, `=`, `?`, `|`, or an operator, found `foo`
+  --> $DIR/bad-name.rs:2:22
+   |
+LL |   let x.y::<isize>.z foo;
+   |                      ^^^ expected one of 9 possible tokens
+
+error: aborting due to 3 previous errors
 

tests/ui/parser/issues/issue-24375.stderr

@@ -3,6 +3,21 @@ error: expected a pattern, found an expression
    |
 LL |         tmp[0] => {}
    |         ^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider moving the expression to a match arm guard
+   |
+LL |         val if val == tmp[0] => {}
+   |         ~~~ ++++++++++++++++
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = tmp[0];
+LL ~     match z {
+LL ~         VAL => {}
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         const { tmp[0] } => {}
+   |         +++++++        +
 
 error: aborting due to 1 previous error
 

tests/ui/parser/pat-lt-bracket-6.stderr

@@ -1,8 +1,8 @@
 error: expected a pattern, found an expression
-  --> $DIR/pat-lt-bracket-6.rs:5:15
+  --> $DIR/pat-lt-bracket-6.rs:5:14
    |
 LL |     let Test(&desc[..]) = x;
-   |               ^^^^^^^^ arbitrary expressions are not allowed in patterns
+   |              ^^^^^^^^^ arbitrary expressions are not allowed in patterns
 
 error[E0308]: mismatched types
   --> $DIR/pat-lt-bracket-6.rs:10:30

tests/ui/parser/recover/recover-pat-exprs.rs

@@ -0,0 +1,106 @@
+// FieldExpression, TupleIndexingExpression
+fn field_access() {
+    match 0 {
+        x => (),
+        x.y => (), //~ error: expected a pattern, found an expression
+        x.0 => (), //~ error: expected a pattern, found an expression
+        x._0 => (), //~ error: expected a pattern, found an expression
+        x.0.1 => (), //~ error: expected a pattern, found an expression
+        x.4.y.17.__z => (), //~ error: expected a pattern, found an expression
+    }
+
+    { let x.0e0; } //~ error: expected one of `:`, `;`, `=`, `@`, or `|`, found `.`
+    { let x.-0.0; } //~ error: expected one of `:`, `;`, `=`, `@`, or `|`, found `.`
+    { let x.-0; } //~ error: expected one of `:`, `;`, `=`, `@`, or `|`, found `.`
+
+    { let x.0u32; } //~ error: expected one of `:`, `;`, `=`, `@`, or `|`, found `.`
+    { let x.0.0_f64; } //~ error: expected one of `:`, `;`, `=`, `@`, or `|`, found `.`
+}
+
+// IndexExpression, ArrayExpression
+fn array_indexing() {
+    match 0 {
+        x[0] => (), //~ error: expected a pattern, found an expression
+        x[..] => (), //~ error: expected a pattern, found an expression
+    }
+
+    { let x[0, 1, 2]; } //~ error: expected one of `:`, `;`, `=`, `@`, or `|`, found `[`
+    { let x[0; 20]; } //~ error: expected one of `:`, `;`, `=`, `@`, or `|`, found `[`
+    { let x[]; } //~ error: expected one of `:`, `;`, `=`, `@`, or `|`, found `[`
+    { let (x[]); } //~ error: expected one of `)`, `,`, `@`, or `|`, found `[`
+    //~^ missing `,`
+}
+
+// MethodCallExpression, CallExpression, ErrorPropagationExpression
+fn method_call() {
+    match 0 {
+        x.f() => (), //~ error: expected a pattern, found an expression
+        x._f() => (), //~ error: expected a pattern, found an expression
+        x? => (), //~ error: expected a pattern, found an expression
+        ().f() => (), //~ error: expected a pattern, found an expression
+        (0, x)?.f() => (), //~ error: expected a pattern, found an expression
+        x.f().g() => (), //~ error: expected a pattern, found an expression
+        0.f()?.g()?? => (), //~ error: expected a pattern, found an expression
+    }
+}
+
+// TypeCastExpression
+fn type_cast() {
+    match 0 {
+        x as usize => (), //~ error: expected a pattern, found an expression
+        0 as usize => (), //~ error: expected a pattern, found an expression
+        x.f().0.4 as f32 => (), //~ error: expected a pattern, found an expression
+    }
+}
+
+// ArithmeticOrLogicalExpression, also check if parentheses are added as needed
+fn operator() {
+    match 0 {
+        1 + 1 => (), //~ error: expected a pattern, found an expression
+        (1 + 2) * 3 => (),
+        //~^ error: expected a pattern, found an expression
+        //~| error: expected a pattern, found an expression
+        x.0 > 2 => (), //~ error: expected a pattern, found an expression
+        x.0 == 2 => (), //~ error: expected a pattern, found an expression
+    }
+
+    // preexisting match arm guard
+    match (0, 0) {
+        (x, y.0 > 2) if x != 0 => (), //~ error: expected a pattern, found an expression
+        (x, y.0 > 2) if x != 0 || x != 1 => (), //~ error: expected a pattern, found an expression
+    }
+}
+
+const _: u32 = match 12 {
+    1 + 2 * PI.cos() => 2, //~ error: expected a pattern, found an expression
+    _ => 0,
+};
+
+fn main() {
+    match u8::MAX {
+        u8::MAX.abs() => (),
+        //~^ error: expected a pattern, found an expression
+        x.sqrt() @ .. => (),
+        //~^ error: expected a pattern, found an expression
+        //~| error: left-hand side of `@` must be a binding
+        z @ w @ v.u() => (),
+        //~^ error: expected a pattern, found an expression
+        y.ilog(3) => (),
+        //~^ error: expected a pattern, found an expression
+        n + 1 => (),
+        //~^ error: expected a pattern, found an expression
+        ("".f() + 14 * 8) => (),
+        //~^ error: expected a pattern, found an expression
+        0 | ((1) | 2) | 3 => (),
+        f?() => (),
+        //~^ error: expected a pattern, found an expression
+        (_ + 1) => (),
+        //~^ error: expected one of `)`, `,`, or `|`, found `+`
+    }
+
+    let 1 + 1 = 2;
+    //~^ error: expected a pattern, found an expression
+
+    let b = matches!(x, (x * x | x.f()) | x[0]);
+    //~^ error: expected one of `)`, `,`, `@`, or `|`, found `*`
+}

tests/ui/parser/recover/recover-pat-issues.rs

@@ -0,0 +1,46 @@
+struct Foo(String);
+struct Bar { baz: String }
+
+fn foo(foo: Foo) -> bool {
+    match foo {
+        Foo("hi".to_owned()) => true,
+        //~^ error: expected a pattern, found an expression
+        _ => false
+    }
+}
+
+fn bar(bar: Bar) -> bool {
+    match bar {
+        Bar { baz: "hi".to_owned() } => true,
+        //~^ error: expected a pattern, found an expression
+        _ => false
+    }
+}
+
+/// Issue #90121
+fn baz() {
+    let foo = vec!["foo".to_string()];
+
+    match foo.as_slice() {
+        &["foo".to_string()] => {}
+        //~^ error: expected a pattern, found an expression
+        _ => {}
+    };
+}
+
+/// Issue #104996
+fn qux() {
+    struct Magic(pub u16);
+    const MAGIC: Magic = Magic(42);
+
+    if let Some(MAGIC.0 as usize) = None::<usize> {}
+    //~^ error: expected a pattern, found an expression
+}
+
+fn main() {
+    if let (-1.some(4)) = (0, Some(4)) {}
+    //~^ error: expected a pattern, found an expression
+
+    if let (-1.Some(4)) = (0, Some(4)) {}
+    //~^ error: expected a pattern, found an expression
+}

tests/ui/parser/recover/recover-pat-issues.stderr

@@ -0,0 +1,113 @@
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-issues.rs:6:13
+   |
+LL |         Foo("hi".to_owned()) => true,
+   |             ^^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider moving the expression to a match arm guard
+   |
+LL |         Foo(val) if val == "hi".to_owned() => true,
+   |             ~~~  +++++++++++++++++++++++++
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = "hi".to_owned();
+LL ~     match foo {
+LL ~         Foo(VAL) => true,
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         Foo(const { "hi".to_owned() }) => true,
+   |             +++++++                 +
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-issues.rs:14:20
+   |
+LL |         Bar { baz: "hi".to_owned() } => true,
+   |                    ^^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider moving the expression to a match arm guard
+   |
+LL |         Bar { baz } if baz == "hi".to_owned() => true,
+   |               ~~~   +++++++++++++++++++++++++
+help: consider extracting the expression into a `const`
+   |
+LL +     const BAZ: /* Type */ = "hi".to_owned();
+LL ~     match bar {
+LL ~         Bar { baz: BAZ } => true,
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         Bar { baz: const { "hi".to_owned() } } => true,
+   |                    +++++++                 +
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-issues.rs:25:11
+   |
+LL |         &["foo".to_string()] => {}
+   |           ^^^^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider moving the expression to a match arm guard
+   |
+LL |         &[val] if val == "foo".to_string() => {}
+   |           ~~~  +++++++++++++++++++++++++++
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = "foo".to_string();
+LL ~     match foo.as_slice() {
+LL ~         &[VAL] => {}
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         &[const { "foo".to_string() }] => {}
+   |           +++++++                   +
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-issues.rs:36:17
+   |
+LL |     if let Some(MAGIC.0 as usize) = None::<usize> {}
+   |                 ^^^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = MAGIC.0 as usize;
+LL ~     if let Some(VAL) = None::<usize> {}
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |     if let Some(const { MAGIC.0 as usize }) = None::<usize> {}
+   |                 +++++++                  +
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-issues.rs:41:13
+   |
+LL |     if let (-1.some(4)) = (0, Some(4)) {}
+   |             ^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = -1.some(4);
+LL ~     if let (VAL) = (0, Some(4)) {}
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |     if let (const { -1.some(4) }) = (0, Some(4)) {}
+   |             +++++++            +
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-issues.rs:44:13
+   |
+LL |     if let (-1.Some(4)) = (0, Some(4)) {}
+   |             ^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = -1.Some(4);
+LL ~     if let (VAL) = (0, Some(4)) {}
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |     if let (const { -1.Some(4) }) = (0, Some(4)) {}
+   |             +++++++            +
+
+error: aborting due to 6 previous errors
+

tests/ui/parser/recover/recover-pat-lets.rs

@@ -0,0 +1,20 @@
+fn main() {
+    let x = Some(2);
+
+    let x.expect("foo");
+    //~^ error: expected a pattern, found an expression
+
+    let x.unwrap(): u32;
+    //~^ error: expected a pattern, found an expression
+
+    let x[0] = 1;
+    //~^ error: expected a pattern, found an expression
+
+    let Some(1 + 1) = x else { //~ error: expected a pattern, found an expression
+        return;
+    };
+
+    if let Some(1 + 1) = x { //~ error: expected a pattern, found an expression
+        return;
+    }
+}

tests/ui/parser/recover/recover-pat-lets.stderr

@@ -0,0 +1,52 @@
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-lets.rs:4:9
+   |
+LL |     let x.expect("foo");
+   |         ^^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-lets.rs:7:9
+   |
+LL |     let x.unwrap(): u32;
+   |         ^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-lets.rs:10:9
+   |
+LL |     let x[0] = 1;
+   |         ^^^^ arbitrary expressions are not allowed in patterns
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-lets.rs:13:14
+   |
+LL |     let Some(1 + 1) = x else {
+   |              ^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = 1 + 1;
+LL ~     let Some(VAL) = x else {
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |     let Some(const { 1 + 1 }) = x else {
+   |              +++++++       +
+
+error: expected a pattern, found an expression
+  --> $DIR/recover-pat-lets.rs:17:17
+   |
+LL |     if let Some(1 + 1) = x {
+   |                 ^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = 1 + 1;
+LL ~     if let Some(VAL) = x {
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |     if let Some(const { 1 + 1 }) = x {
+   |                 +++++++       +
+
+error: aborting due to 5 previous errors
+

tests/ui/parser/pat-recover-ranges.rs → tests/ui/parser/recover/recover-pat-ranges.rs

@@ -22,8 +22,8 @@ fn main() {
         //~| warning: `...` range patterns are deprecated
         //~| warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
         0.x()..="y".z() => (),
-        //~^ error: expected a pattern range bound, found a method call
-        //~| error: expected a pattern range bound, found a method call
+        //~^ error: expected a pattern range bound, found an expression
+        //~| error: expected a pattern range bound, found an expression
     };
 }
 

tests/ui/parser/recover/recover-pat-ranges.stderr

@@ -0,0 +1,216 @@
+error: range pattern bounds cannot have parentheses
+  --> $DIR/recover-pat-ranges.rs:4:13
+   |
+LL |         0..=(1) => (),
+   |             ^ ^
+   |
+help: remove these parentheses
+   |
+LL -         0..=(1) => (),
+LL +         0..=1 => (),
+   |
+
+error: range pattern bounds cannot have parentheses
+  --> $DIR/recover-pat-ranges.rs:6:9
+   |
+LL |         (-12)..=4 => (),
+   |         ^   ^
+   |
+help: remove these parentheses
+   |
+LL -         (-12)..=4 => (),
+LL +         -12..=4 => (),
+   |
+
+error: range pattern bounds cannot have parentheses
+  --> $DIR/recover-pat-ranges.rs:8:9
+   |
+LL |         (0)..=(-4) => (),
+   |         ^ ^
+   |
+help: remove these parentheses
+   |
+LL -         (0)..=(-4) => (),
+LL +         0..=(-4) => (),
+   |
+
+error: range pattern bounds cannot have parentheses
+  --> $DIR/recover-pat-ranges.rs:8:15
+   |
+LL |         (0)..=(-4) => (),
+   |               ^  ^
+   |
+help: remove these parentheses
+   |
+LL -         (0)..=(-4) => (),
+LL +         (0)..=-4 => (),
+   |
+
+error: range pattern bounds cannot have parentheses
+  --> $DIR/recover-pat-ranges.rs:13:9
+   |
+LL |         (4).. => (),
+   |         ^ ^
+   |
+help: remove these parentheses
+   |
+LL -         (4).. => (),
+LL +         4.. => (),
+   |
+
+error: range pattern bounds cannot have parentheses
+  --> $DIR/recover-pat-ranges.rs:15:9
+   |
+LL |         (-4 + 0).. => (),
+   |         ^      ^
+   |
+help: remove these parentheses
+   |
+LL -         (-4 + 0).. => (),
+LL +         -4 + 0.. => (),
+   |
+
+error: range pattern bounds cannot have parentheses
+  --> $DIR/recover-pat-ranges.rs:18:9
+   |
+LL |         (1 + 4)...1 * 2 => (),
+   |         ^     ^
+   |
+help: remove these parentheses
+   |
+LL -         (1 + 4)...1 * 2 => (),
+LL +         1 + 4...1 * 2 => (),
+   |
+
+error: expected a pattern range bound, found an expression
+  --> $DIR/recover-pat-ranges.rs:11:12
+   |
+LL |         ..=1 + 2 => (),
+   |            ^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = 1 + 2;
+LL ~     match -1 {
+LL |         0..=1 => (),
+...
+LL |
+LL ~         ..=VAL => (),
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         ..=const { 1 + 2 } => (),
+   |            +++++++       +
+
+error: expected a pattern range bound, found an expression
+  --> $DIR/recover-pat-ranges.rs:15:10
+   |
+LL |         (-4 + 0).. => (),
+   |          ^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = -4 + 0;
+LL ~     match -1 {
+LL |         0..=1 => (),
+...
+LL |
+LL ~         (VAL).. => (),
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         (const { -4 + 0 }).. => (),
+   |          +++++++        +
+
+error: expected a pattern range bound, found an expression
+  --> $DIR/recover-pat-ranges.rs:18:10
+   |
+LL |         (1 + 4)...1 * 2 => (),
+   |          ^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = 1 + 4;
+LL ~     match -1 {
+LL |         0..=1 => (),
+...
+LL |
+LL ~         (VAL)...1 * 2 => (),
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         (const { 1 + 4 })...1 * 2 => (),
+   |          +++++++       +
+
+error: expected a pattern range bound, found an expression
+  --> $DIR/recover-pat-ranges.rs:18:19
+   |
+LL |         (1 + 4)...1 * 2 => (),
+   |                   ^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = 1 * 2;
+LL ~     match -1 {
+LL |         0..=1 => (),
+...
+LL |
+LL ~         (1 + 4)...VAL => (),
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         (1 + 4)...const { 1 * 2 } => (),
+   |                   +++++++       +
+
+error: expected a pattern range bound, found an expression
+  --> $DIR/recover-pat-ranges.rs:24:9
+   |
+LL |         0.x()..="y".z() => (),
+   |         ^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = 0.x();
+LL ~     match -1 {
+LL |         0..=1 => (),
+...
+LL |
+LL ~         VAL..="y".z() => (),
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         const { 0.x() }..="y".z() => (),
+   |         +++++++       +
+
+error: expected a pattern range bound, found an expression
+  --> $DIR/recover-pat-ranges.rs:24:17
+   |
+LL |         0.x()..="y".z() => (),
+   |                 ^^^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = "y".z();
+LL ~     match -1 {
+LL |         0..=1 => (),
+...
+LL |
+LL ~         0.x()..=VAL => (),
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         0.x()..=const { "y".z() } => (),
+   |                 +++++++         +
+
+warning: `...` range patterns are deprecated
+  --> $DIR/recover-pat-ranges.rs:18:16
+   |
+LL |         (1 + 4)...1 * 2 => (),
+   |                ^^^ help: use `..=` for an inclusive range
+   |
+   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
+   = note: `#[warn(ellipsis_inclusive_range_patterns)]` on by default
+
+error: aborting due to 13 previous errors; 1 warning emitted
+

tests/ui/parser/pat-recover-wildcards.stderr → tests/ui/parser/recover/recover-pat-wildcards.stderr

@@ -1,35 +1,35 @@
 error: expected one of `=>`, `if`, or `|`, found `+`
-  --> $DIR/pat-recover-wildcards.rs:5:11
+  --> $DIR/recover-pat-wildcards.rs:5:11
    |
 LL |         _ + 1 => ()
    |           ^ expected one of `=>`, `if`, or `|`
 
 error: expected one of `)`, `,`, or `|`, found `%`
-  --> $DIR/pat-recover-wildcards.rs:11:12
+  --> $DIR/recover-pat-wildcards.rs:11:12
    |
 LL |         (_ % 4) => ()
    |            ^ expected one of `)`, `,`, or `|`
 
 error: expected one of `=>`, `if`, or `|`, found `.`
-  --> $DIR/pat-recover-wildcards.rs:17:10
+  --> $DIR/recover-pat-wildcards.rs:17:10
    |
 LL |         _.x() => ()
    |          ^ expected one of `=>`, `if`, or `|`
 
 error: expected one of `=>`, `if`, or `|`, found `..=`
-  --> $DIR/pat-recover-wildcards.rs:23:10
+  --> $DIR/recover-pat-wildcards.rs:23:10
    |
 LL |         _..=4 => ()
    |          ^^^ expected one of `=>`, `if`, or `|`
 
 error: expected one of `=>`, `if`, or `|`, found reserved identifier `_`
-  --> $DIR/pat-recover-wildcards.rs:29:11
+  --> $DIR/recover-pat-wildcards.rs:29:11
    |
 LL |         .._ => ()
    |           ^ expected one of `=>`, `if`, or `|`
 
 error[E0586]: inclusive range with no end
-  --> $DIR/pat-recover-wildcards.rs:35:10
+  --> $DIR/recover-pat-wildcards.rs:35:10
    |
 LL |         0..._ => ()
    |          ^^^
@@ -42,31 +42,25 @@ LL +         0.._ => ()
    |
 
 error: expected one of `=>`, `if`, or `|`, found reserved identifier `_`
-  --> $DIR/pat-recover-wildcards.rs:35:13
+  --> $DIR/recover-pat-wildcards.rs:35:13
    |
 LL |         0..._ => ()
    |             ^ expected one of `=>`, `if`, or `|`
 
 error: expected one of `)`, `,`, or `|`, found `*`
-  --> $DIR/pat-recover-wildcards.rs:43:12
+  --> $DIR/recover-pat-wildcards.rs:43:12
    |
 LL |         (_ * 0)..5 => ()
    |            ^ expected one of `)`, `,`, or `|`
 
 error: expected one of `=>`, `if`, or `|`, found `(`
-  --> $DIR/pat-recover-wildcards.rs:49:11
+  --> $DIR/recover-pat-wildcards.rs:49:11
    |
 LL |         ..(_) => ()
    |           ^ expected one of `=>`, `if`, or `|`
 
-error: expected a pattern range bound, found an expression
-  --> $DIR/pat-recover-wildcards.rs:55:14
-   |
-LL |         4..=(2 + _) => ()
-   |              ^^^^^ arbitrary expressions are not allowed in patterns
-
 error: range pattern bounds cannot have parentheses
-  --> $DIR/pat-recover-wildcards.rs:55:13
+  --> $DIR/recover-pat-wildcards.rs:55:13
    |
 LL |         4..=(2 + _) => ()
    |             ^     ^
@@ -77,6 +71,23 @@ LL -         4..=(2 + _) => ()
 LL +         4..=2 + _ => ()
    |
 
+error: expected a pattern range bound, found an expression
+  --> $DIR/recover-pat-wildcards.rs:55:14
+   |
+LL |         4..=(2 + _) => ()
+   |              ^^^^^ arbitrary expressions are not allowed in patterns
+   |
+help: consider extracting the expression into a `const`
+   |
+LL +     const VAL: /* Type */ = 2 + _;
+LL ~     match 9 {
+LL ~         4..=(VAL) => ()
+   |
+help: consider wrapping the expression in an inline `const` (requires `#![feature(inline_const_pat)]`)
+   |
+LL |         4..=(const { 2 + _ }) => ()
+   |              +++++++       +
+
 error: aborting due to 11 previous errors
 
 For more information about this error, try `rustc --explain E0586`.