Auto merge of #55893 - pnkfelix:issue-55810-beta-backport-of-pr-55819, r=estebank

[beta] backport rollup (typeck match arms eagerly; add rustc_promotable to unsigneds)

Backport of 5f91373 from (beta-accepted) PR #55819

Fix #55810
Fix #55806

Author: bors

src/libcore/num/mod.rs

@@ -2152,6 +2152,7 @@ Basic usage:
 ", $Feature, "assert_eq!(", stringify!($SelfT), "::min_value(), 0);", $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
+            #[rustc_promotable]
             #[inline]
             pub const fn min_value() -> Self { 0 }
         }
@@ -2168,6 +2169,7 @@ Basic usage:
 stringify!($MaxV), ");", $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
+            #[rustc_promotable]
             #[inline]
             pub const fn max_value() -> Self { !0 }
         }

src/librustc_typeck/check/_match.rs

@@ -626,9 +626,9 @@ https://doc.rust-lang.org/reference/types.html#trait-objects");
         let discrim_diverges = self.diverges.get();
         self.diverges.set(Diverges::Maybe);
 
-        // Typecheck the patterns first, so that we get types for all the
-        // bindings.
-        let all_arm_pats_diverge = arms.iter().map(|arm| {
+        // rust-lang/rust#55810: Typecheck patterns first (via eager
+        // collection into `Vec`), so we get types for all bindings.
+        let all_arm_pats_diverge: Vec<_> = arms.iter().map(|arm| {
             let mut all_pats_diverge = Diverges::WarnedAlways;
             for p in &arm.pats {
                 self.diverges.set(Diverges::Maybe);
@@ -644,7 +644,7 @@ https://doc.rust-lang.org/reference/types.html#trait-objects");
                 Diverges::Maybe => Diverges::Maybe,
                 Diverges::Always | Diverges::WarnedAlways => Diverges::WarnedAlways,
             }
-        });
+        }).collect();
 
         // Now typecheck the blocks.
         //

src/test/ui/consts/auxiliary/promotable_const_fn_lib.rs

@@ -0,0 +1,31 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Crate that exports a const fn. Used for testing cross-crate.
+
+#![feature(staged_api, rustc_attrs)]
+#![stable(since="1.0.0", feature = "mep")]
+
+#![crate_type="rlib"]
+
+#[rustc_promotable]
+#[stable(since="1.0.0", feature = "mep")]
+#[inline]
+pub const fn foo() -> usize { 22 }
+
+#[stable(since="1.0.0", feature = "mep")]
+pub struct Foo(usize);
+
+impl Foo {
+    #[stable(since="1.0.0", feature = "mep")]
+    #[inline]
+    #[rustc_promotable]
+    pub const fn foo() -> usize { 22 }
+}

src/test/ui/consts/promote_fn_calls.rs

@@ -0,0 +1,13 @@
+// compile-pass
+// aux-build:promotable_const_fn_lib.rs
+
+#![feature(nll)]
+
+extern crate promotable_const_fn_lib;
+
+use promotable_const_fn_lib::{foo, Foo};
+
+fn main() {
+    let x: &'static usize = &foo();
+    let x: &'static usize = &Foo::foo();
+}

src/test/ui/consts/promote_fn_calls_std.rs

@@ -0,0 +1,30 @@
+// compile-pass
+
+#![feature(nll)]
+
+fn main() {
+    let x: &'static u8 = &u8::max_value();
+    let x: &'static u16 = &u16::max_value();
+    let x: &'static u32 = &u32::max_value();
+    let x: &'static u64 = &u64::max_value();
+    let x: &'static u128 = &u128::max_value();
+    let x: &'static usize = &usize::max_value();
+    let x: &'static u8 = &u8::min_value();
+    let x: &'static u16 = &u16::min_value();
+    let x: &'static u32 = &u32::min_value();
+    let x: &'static u64 = &u64::min_value();
+    let x: &'static u128 = &u128::min_value();
+    let x: &'static usize = &usize::min_value();
+    let x: &'static i8 = &i8::max_value();
+    let x: &'static i16 = &i16::max_value();
+    let x: &'static i32 = &i32::max_value();
+    let x: &'static i64 = &i64::max_value();
+    let x: &'static i128 = &i128::max_value();
+    let x: &'static isize = &isize::max_value();
+    let x: &'static i8 = &i8::min_value();
+    let x: &'static i16 = &i16::min_value();
+    let x: &'static i32 = &i32::min_value();
+    let x: &'static i64 = &i64::min_value();
+    let x: &'static i128 = &i128::min_value();
+    let x: &'static isize = &isize::min_value();
+}

src/test/ui/typeck/issue-55810-must-typeck-match-pats-before-guards.rs

@@ -0,0 +1,23 @@
+// compile-pass
+
+// rust-lang/rust#55810: types for a binding in a match arm can be
+// inferred from arms that come later in the match.
+
+struct S;
+
+impl S {
+    fn method(&self) -> bool {
+        unimplemented!()
+    }
+}
+
+fn get<T>() -> T {
+    unimplemented!()
+}
+
+fn main() {
+    match get() {
+        x if x.method() => {}
+        &S => {}
+    }
+}