Auto merge of #45050 - petrochenkov:ambind, r=nikomatsakis
resolve: Use same rules for disambiguating fresh bindings in `match` and `let` Resolve `Unit` as a unit struct pattern in ```rust struct Unit; let Unit = x; ``` consistently with ```rust match x { Unit => {} } ``` It was previously an error. (The change also applies to unit variants and constants.) Fixes https://users.rust-lang.org/t/e0530-cannot-shadow-unit-structs-what-in-the-earthly-what/13054 (This particular change doesn't depend on a fix for the issue mentioned in https://users.rust-lang.org/t/e0530-cannot-shadow-unit-structs-what-in-the-earthly-what/13054/4) cc @rust-lang/lang r? @nikomatsakis
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commit
a35a3abcda
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@ -260,7 +260,14 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
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"refutable pattern in {}: `{}` not covered",
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origin, pattern_string
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);
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diag.span_label(pat.span, format!("pattern `{}` not covered", pattern_string));
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let label_msg = match pat.node {
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PatKind::Path(hir::QPath::Resolved(None, ref path))
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if path.segments.len() == 1 && path.segments[0].parameters.is_none() => {
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format!("interpreted as a {} pattern, not new variable", path.def.kind_name())
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}
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_ => format!("pattern `{}` not covered", pattern_string),
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};
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diag.span_label(pat.span, label_msg);
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diag.emit();
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});
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}
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@ -377,12 +377,6 @@ enum PatternSource {
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}
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impl PatternSource {
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fn is_refutable(self) -> bool {
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match self {
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PatternSource::Match | PatternSource::IfLet | PatternSource::WhileLet => true,
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PatternSource::Let | PatternSource::For | PatternSource::FnParam => false,
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}
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}
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fn descr(self) -> &'static str {
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match self {
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PatternSource::Match => "match binding",
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@ -2388,20 +2382,24 @@ impl<'a> Resolver<'a> {
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false, pat.span)
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.and_then(LexicalScopeBinding::item);
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let resolution = binding.map(NameBinding::def).and_then(|def| {
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let ivmode = BindingMode::ByValue(Mutability::Immutable);
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let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
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bmode != ivmode;
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let is_syntactic_ambiguity = opt_pat.is_none() &&
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bmode == BindingMode::ByValue(Mutability::Immutable);
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match def {
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Def::StructCtor(_, CtorKind::Const) |
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Def::VariantCtor(_, CtorKind::Const) |
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Def::Const(..) if !always_binding => {
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// A unit struct/variant or constant pattern.
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Def::Const(..) if is_syntactic_ambiguity => {
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// Disambiguate in favor of a unit struct/variant
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// or constant pattern.
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self.record_use(ident.node, ValueNS, binding.unwrap(), ident.span);
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Some(PathResolution::new(def))
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}
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Def::StructCtor(..) | Def::VariantCtor(..) |
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Def::Const(..) | Def::Static(..) => {
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// A fresh binding that shadows something unacceptable.
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// This is unambiguously a fresh binding, either syntactically
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// (e.g. `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves
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// to something unusable as a pattern (e.g. constructor function),
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// but we still conservatively report an error, see
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// issues/33118#issuecomment-233962221 for one reason why.
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resolve_error(
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self,
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ident.span,
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@ -2410,7 +2408,7 @@ impl<'a> Resolver<'a> {
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);
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None
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}
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Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
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Def::Fn(..) | Def::Err => {
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// These entities are explicitly allowed
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// to be shadowed by fresh bindings.
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None
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@ -12,6 +12,6 @@ mod foo { pub struct bar; }
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fn main() {
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let bar = 5;
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//~^ ERROR let bindings cannot shadow unit structs
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//~^ ERROR mismatched types
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use foo::bar;
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}
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@ -14,6 +14,6 @@ struct Test;
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fn main() {
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|| {
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let Test = 1; //~ ERROR let bindings cannot shadow unit structs
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let Test = 1; //~ ERROR mismatched types
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};
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}
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@ -0,0 +1,67 @@
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// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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struct UnitStruct;
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struct TupleStruct();
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struct BracedStruct{}
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enum E {
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UnitVariant,
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TupleVariant(),
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BracedVariant{},
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}
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use E::*;
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const CONST: () = ();
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static STATIC: () = ();
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fn function() {}
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fn main() {
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let doesnt_matter = 0;
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match UnitStruct {
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UnitStruct => {} // OK, `UnitStruct` is a unit struct pattern
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}
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match doesnt_matter {
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TupleStruct => {} //~ ERROR match bindings cannot shadow tuple structs
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}
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match doesnt_matter {
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BracedStruct => {} // OK, `BracedStruct` is a fresh binding
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}
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match UnitVariant {
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UnitVariant => {} // OK, `UnitVariant` is a unit variant pattern
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}
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match doesnt_matter {
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TupleVariant => {} //~ ERROR match bindings cannot shadow tuple variants
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}
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match doesnt_matter {
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BracedVariant => {} //~ ERROR match bindings cannot shadow struct variants
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}
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match CONST {
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CONST => {} // OK, `CONST` is a const pattern
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}
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match doesnt_matter {
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STATIC => {} //~ ERROR match bindings cannot shadow statics
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}
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match doesnt_matter {
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function => {} // OK, `function` is a fresh binding
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}
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let UnitStruct = UnitStruct; // OK, `UnitStruct` is a unit struct pattern
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let TupleStruct = doesnt_matter; //~ ERROR let bindings cannot shadow tuple structs
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let BracedStruct = doesnt_matter; // OK, `BracedStruct` is a fresh binding
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let UnitVariant = UnitVariant; // OK, `UnitVariant` is a unit variant pattern
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let TupleVariant = doesnt_matter; //~ ERROR let bindings cannot shadow tuple variants
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let BracedVariant = doesnt_matter; //~ ERROR let bindings cannot shadow struct variants
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let CONST = CONST; // OK, `CONST` is a const pattern
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let STATIC = doesnt_matter; //~ ERROR let bindings cannot shadow statics
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let function = doesnt_matter; // OK, `function` is a fresh binding
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}
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@ -13,17 +13,14 @@ mod foo {
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pub const d: u8 = 2;
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}
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use foo::b as c; //~ NOTE is imported here
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use foo::d; //~ NOTE is imported here
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use foo::b as c;
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use foo::d;
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const a: u8 = 2; //~ NOTE is defined here
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const a: u8 = 2;
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fn main() {
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let a = 4; //~ ERROR let bindings cannot shadow constants
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//~^ NOTE cannot be named the same as a constant
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let c = 4; //~ ERROR let bindings cannot shadow constants
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//~^ NOTE cannot be named the same as a constant
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let d = 4; //~ ERROR let bindings cannot shadow constants
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//~^ NOTE cannot be named the same as a constant
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let a = 4; //~ ERROR refutable pattern in local binding: `_` not covered
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let c = 4; //~ ERROR refutable pattern in local binding: `_` not covered
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let d = 4; //~ ERROR refutable pattern in local binding: `_` not covered
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fn f() {} // Check that the `NOTE`s still work with an item here (c.f. issue #35115).
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}
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@ -0,0 +1,20 @@
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error[E0005]: refutable pattern in local binding: `_` not covered
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--> $DIR/const-pattern-irrefutable.rs:22:9
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22 | let a = 4; //~ ERROR refutable pattern in local binding: `_` not covered
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| ^ interpreted as a constant pattern, not new variable
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error[E0005]: refutable pattern in local binding: `_` not covered
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--> $DIR/const-pattern-irrefutable.rs:23:9
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23 | let c = 4; //~ ERROR refutable pattern in local binding: `_` not covered
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| ^ interpreted as a constant pattern, not new variable
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error[E0005]: refutable pattern in local binding: `_` not covered
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--> $DIR/const-pattern-irrefutable.rs:24:9
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24 | let d = 4; //~ ERROR refutable pattern in local binding: `_` not covered
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| ^ interpreted as a constant pattern, not new variable
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error: aborting due to 3 previous errors
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@ -8,11 +8,6 @@
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::option::*;
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fn main() {
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let None: isize = 42; //~ ERROR let bindings cannot shadow unit variants
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log(debug, None);
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//~^ ERROR cannot find function `log` in this scope
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//~| ERROR cannot find value `debug` in this scope
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let None: isize = 42; //~ ERROR mismatched types
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}
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@ -0,0 +1,11 @@
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error[E0308]: mismatched types
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--> $DIR/name-clash-nullary.rs:12:7
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12 | let None: isize = 42; //~ ERROR mismatched types
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| ^^^^ expected isize, found enum `std::option::Option`
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= note: expected type `isize`
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found type `std::option::Option<_>`
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error: aborting due to previous error
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