Auto merge of rust-lang#87980 - Manishearth:rollup-vkuix3y, r=Manishearth

Rollup of 4 pull requests

Successful merges:

 - rust-lang#87916 (Implement `black_box` using intrinsic)
 - rust-lang#87922 (Add c_enum_min_bits target spec field, use for arm-none and thumb-none targets)
 - rust-lang#87953 (Improve formatting of closure capture migration suggestion for multi-line closures.)
 - rust-lang#87965 (Silence non_fmt_panic from external macros.)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_lint/src/non_fmt_panic.rs

@@ -2,6 +2,7 @@ use crate::{LateContext, LateLintPass, LintContext};
 use rustc_ast as ast;
 use rustc_errors::{pluralize, Applicability};
 use rustc_hir as hir;
+use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty;
 use rustc_parse_format::{ParseMode, Parser, Piece};
 use rustc_session::lint::FutureIncompatibilityReason;
@@ -75,6 +76,11 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
 
     let (span, panic, symbol_str) = panic_call(cx, f);
 
+    if in_external_macro(cx.sess(), span) {
+        // Nothing that can be done about it in the current crate.
+        return;
+    }
+
     // Find the span of the argument to `panic!()`, before expansion in the
     // case of `panic!(some_macro!())`.
     // We don't use source_callsite(), because this `panic!(..)` might itself
@@ -152,6 +158,13 @@ fn check_panic_str<'tcx>(
         return;
     }
 
+    let (span, _, _) = panic_call(cx, f);
+
+    if in_external_macro(cx.sess(), span) && in_external_macro(cx.sess(), arg.span) {
+        // Nothing that can be done about it in the current crate.
+        return;
+    }
+
     let fmt_span = arg.span.source_callsite();
 
     let (snippet, style) = match cx.sess().parse_sess.source_map().span_to_snippet(fmt_span) {
@@ -167,8 +180,6 @@ fn check_panic_str<'tcx>(
         Parser::new(fmt.as_ref(), style, snippet.clone(), false, ParseMode::Format);
     let n_arguments = (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
 
-    let (span, _, _) = panic_call(cx, f);
-
     if n_arguments > 0 && fmt_parser.errors.is_empty() {
         let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] {
             [] => vec![fmt_span],

compiler/rustc_middle/src/ty/layout.rs

@@ -112,9 +112,6 @@ impl IntegerExt for Integer {
         let unsigned_fit = Integer::fit_unsigned(cmp::max(min as u128, max as u128));
         let signed_fit = cmp::max(Integer::fit_signed(min), Integer::fit_signed(max));
 
-        let mut min_from_extern = None;
-        let min_default = I8;
-
         if let Some(ity) = repr.int {
             let discr = Integer::from_attr(&tcx, ity);
             let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
@@ -128,19 +125,14 @@ impl IntegerExt for Integer {
             return (discr, ity.is_signed());
         }
 
-        if repr.c() {
-            match &tcx.sess.target.arch[..] {
-                "hexagon" => min_from_extern = Some(I8),
-                // WARNING: the ARM EABI has two variants; the one corresponding
-                // to `at_least == I32` appears to be used on Linux and NetBSD,
-                // but some systems may use the variant corresponding to no
-                // lower bound. However, we don't run on those yet...?
-                "arm" => min_from_extern = Some(I32),
-                _ => min_from_extern = Some(I32),
-            }
-        }
-
-        let at_least = min_from_extern.unwrap_or(min_default);
+        let at_least = if repr.c() {
+            // This is usually I32, however it can be different on some platforms,
+            // notably hexagon and arm-none/thumb-none
+            tcx.data_layout().c_enum_min_size
+        } else {
+            // repr(Rust) enums try to be as small as possible
+            I8
+        };
 
         // If there are no negative values, we can use the unsigned fit.
         if min >= 0 {

compiler/rustc_target/src/abi/mod.rs

@@ -36,6 +36,9 @@ pub struct TargetDataLayout {
     pub vector_align: Vec<(Size, AbiAndPrefAlign)>,
 
     pub instruction_address_space: AddressSpace,
+
+    /// Minimum size of #[repr(C)] enums (default I32 bits)
+    pub c_enum_min_size: Integer,
 }
 
 impl Default for TargetDataLayout {
@@ -60,6 +63,7 @@ impl Default for TargetDataLayout {
                 (Size::from_bits(128), AbiAndPrefAlign::new(align(128))),
             ],
             instruction_address_space: AddressSpace::DATA,
+            c_enum_min_size: Integer::I32,
         }
     }
 }
@@ -173,6 +177,8 @@ impl TargetDataLayout {
             ));
         }
 
+        dl.c_enum_min_size = Integer::from_size(Size::from_bits(target.c_enum_min_bits))?;
+
         Ok(dl)
     }
 
@@ -610,6 +616,17 @@ impl Integer {
         }
         I8
     }
+
+    fn from_size(size: Size) -> Result<Self, String> {
+        match size.bits() {
+            8 => Ok(Integer::I8),
+            16 => Ok(Integer::I16),
+            32 => Ok(Integer::I32),
+            64 => Ok(Integer::I64),
+            128 => Ok(Integer::I128),
+            _ => Err(format!("rust does not support integers with {} bits", size.bits())),
+        }
+    }
 }
 
 /// Fundamental unit of memory access and layout.

compiler/rustc_target/src/spec/armebv7r_none_eabi.rs

@@ -20,6 +20,8 @@ pub fn target() -> Target {
             panic_strategy: PanicStrategy::Abort,
             max_atomic_width: Some(32),
             emit_debug_gdb_scripts: false,
+            // GCC and Clang default to 8 for arm-none here
+            c_enum_min_bits: 8,
             ..Default::default()
         },
     }

compiler/rustc_target/src/spec/armebv7r_none_eabihf.rs

@@ -21,6 +21,8 @@ pub fn target() -> Target {
             features: "+vfp3,-d32,-fp16".to_string(),
             max_atomic_width: Some(32),
             emit_debug_gdb_scripts: false,
+            // GCC and Clang default to 8 for arm-none here
+            c_enum_min_bits: 8,
             ..Default::default()
         },
     }

compiler/rustc_target/src/spec/armv7a_none_eabi.rs

@@ -28,6 +28,7 @@ pub fn target() -> Target {
         max_atomic_width: Some(64),
         panic_strategy: PanicStrategy::Abort,
         emit_debug_gdb_scripts: false,
+        c_enum_min_bits: 8,
         ..Default::default()
     };
     Target {

compiler/rustc_target/src/spec/armv7a_none_eabihf.rs

@@ -19,6 +19,8 @@ pub fn target() -> Target {
         max_atomic_width: Some(64),
         panic_strategy: PanicStrategy::Abort,
         emit_debug_gdb_scripts: false,
+        // GCC and Clang default to 8 for arm-none here
+        c_enum_min_bits: 8,
         ..Default::default()
     };
     Target {

compiler/rustc_target/src/spec/armv7r_none_eabi.rs

@@ -19,6 +19,8 @@ pub fn target() -> Target {
             panic_strategy: PanicStrategy::Abort,
             max_atomic_width: Some(32),
             emit_debug_gdb_scripts: false,
+            // GCC and Clang default to 8 for arm-none here
+            c_enum_min_bits: 8,
             ..Default::default()
         },
     }

compiler/rustc_target/src/spec/armv7r_none_eabihf.rs

@@ -20,6 +20,8 @@ pub fn target() -> Target {
             features: "+vfp3,-d32,-fp16".to_string(),
             max_atomic_width: Some(32),
             emit_debug_gdb_scripts: false,
+            // GCC and Clang default to 8 for arm-none here
+            c_enum_min_bits: 8,
             ..Default::default()
         },
     }

compiler/rustc_target/src/spec/hexagon_unknown_linux_musl.rs

@@ -13,6 +13,8 @@ pub fn target() -> Target {
     base.dynamic_linking = true;
     base.executables = true;
 
+    base.c_enum_min_bits = 8;
+
     Target {
         llvm_target: "hexagon-unknown-linux-musl".to_string(),
         pointer_width: 32,

compiler/rustc_target/src/spec/mod.rs

@@ -1336,6 +1336,9 @@ pub struct TargetOptions {
 
     /// If present it's a default value to use for adjusting the C ABI.
     pub default_adjusted_cabi: Option<Abi>,
+
+    /// Minimum number of bits in #[repr(C)] enum. Defaults to 32.
+    pub c_enum_min_bits: u64,
 }
 
 impl Default for TargetOptions {
@@ -1440,6 +1443,7 @@ impl Default for TargetOptions {
             split_debuginfo: SplitDebuginfo::Off,
             supported_sanitizers: SanitizerSet::empty(),
             default_adjusted_cabi: None,
+            c_enum_min_bits: 32,
         }
     }
 }
@@ -1604,6 +1608,12 @@ impl Target {
                     base.$key_name = s;
                 }
             } );
+            ($key_name:ident, u64) => ( {
+                let name = (stringify!($key_name)).replace("_", "-");
+                if let Some(s) = obj.remove_key(&name).and_then(|j| Json::as_u64(&j)) {
+                    base.$key_name = s;
+                }
+            } );
             ($key_name:ident, Option<u32>) => ( {
                 let name = (stringify!($key_name)).replace("_", "-");
                 if let Some(s) = obj.remove_key(&name).and_then(|j| Json::as_u64(&j)) {
@@ -2017,6 +2027,7 @@ impl Target {
         key!(split_debuginfo, SplitDebuginfo)?;
         key!(supported_sanitizers, SanitizerSet)?;
         key!(default_adjusted_cabi, Option<Abi>)?;
+        key!(c_enum_min_bits, u64);
 
         if base.is_builtin {
             // This can cause unfortunate ICEs later down the line.
@@ -2255,6 +2266,7 @@ impl ToJson for Target {
         target_option_val!(has_thumb_interworking);
         target_option_val!(split_debuginfo);
         target_option_val!(supported_sanitizers);
+        target_option_val!(c_enum_min_bits);
 
         if let Some(abi) = self.default_adjusted_cabi {
             d.insert("default-adjusted-cabi".to_string(), Abi::name(abi).to_json());

compiler/rustc_target/src/spec/thumb_base.rs

@@ -53,6 +53,9 @@ pub fn opts() -> TargetOptions {
         // LLVM is eager to trash the link register when calling `noreturn` functions, which
         // breaks debugging. Preserve LR by default to prevent that from happening.
         frame_pointer: FramePointer::Always,
+        // ARM supports multiple ABIs for enums, the linux one matches the default of 32 here
+        // but any arm-none or thumb-none target will be defaulted to 8 on GCC and clang
+        c_enum_min_bits: 8,
         ..Default::default()
     }
 }

compiler/rustc_typeck/src/check/upvar.rs

@@ -649,11 +649,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         match self.tcx.sess.source_map().span_to_snippet(closure_body_span) {
                             Ok(s) => {
                                 let trimmed = s.trim_start();
+                                let mut lines = trimmed.lines();
+                                let line1 = lines.next().unwrap_or_default();
 
                                 // If the closure contains a block then replace the opening brace
                                 // with "{ let _ = (..); "
-                                let sugg = if let Some('{') = trimmed.chars().next() {
-                                    format!("{{ {}; {}", migration_string, &trimmed[1..])
+                                let sugg = if line1.trim_end() == "{" {
+                                    // This is a multi-line closure with just a `{` on the first line,
+                                    // so we put the `let` on its own line.
+                                    // We take the indentation from the next non-empty line.
+                                    let line2 = lines.filter(|line| !line.is_empty()).next().unwrap_or_default();
+                                    let indent = line2.split_once(|c: char| !c.is_whitespace()).unwrap_or_default().0;
+                                    format!("{{\n{}{};{}", indent, migration_string, &trimmed[line1.len()..])
+                                } else if line1.starts_with('{') {
+                                    format!("{{ {}; {}", migration_string, &trimmed[1..].trim_start())
                                 } else {
                                     format!("{{ {}; {} }}", migration_string, s)
                                 };

src/test/ui/auxiliary/fancy-panic.rs

@@ -1,5 +1,8 @@
 #[macro_export]
 macro_rules! fancy_panic {
+    () => {
+        panic!("{}");
+    };
     ($msg:expr) => {
         panic!($msg)
     };

src/test/ui/closures/2229_closure_analysis/migrations/auto_traits.fixed

@@ -55,7 +55,8 @@ impl Clone for U {
 
 fn test_clone_trait() {
     let f = U(S(String::from("Hello World")), T(0));
-    let c = || { let _ = &f; 
+    let c = || {
+        let _ = &f;
         //~^ ERROR: `Clone` trait implementation for closure and drop order
         //~| NOTE: in Rust 2018, this closure would implement `Clone` as `f` implements `Clone`, but in Rust 2021, this closure would no longer implement `Clone` as `f.1` does not implement `Clone`
         //~| NOTE: for more information, see

src/test/ui/closures/2229_closure_analysis/migrations/auto_traits.stderr

@@ -58,12 +58,12 @@ LL | }
    = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/disjoint-capture-in-closures.html>
 help: add a dummy let to cause `f` to be fully captured
    |
-LL ~     let c = || { let _ = &f; 
+LL ~     let c = || {
+LL +         let _ = &f;
 LL +
 LL +
 LL +
 LL +
-LL +         let f_1 = f.1;
  ...
 
 error: aborting due to 3 previous errors

src/test/ui/closures/2229_closure_analysis/migrations/insignificant_drop.fixed

@@ -12,7 +12,8 @@ fn test1_all_need_migration() {
     let t1 = (String::new(), String::new());
     let t2 = (String::new(), String::new());
 
-    let c = || { let _ = (&t, &t1, &t2); 
+    let c = || {
+        let _ = (&t, &t1, &t2);
         //~^ ERROR: drop order
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t`, `t1`, `t2` to be fully captured
@@ -38,7 +39,8 @@ fn test2_only_precise_paths_need_migration() {
     let t1 = (String::new(), String::new());
     let t2 = (String::new(), String::new());
 
-    let c = || { let _ = (&t, &t1); 
+    let c = || {
+        let _ = (&t, &t1);
         //~^ ERROR: drop order
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t`, `t1` to be fully captured
@@ -59,7 +61,8 @@ fn test2_only_precise_paths_need_migration() {
 fn test3_only_by_value_need_migration() {
     let t = (String::new(), String::new());
     let t1 = (String::new(), String::new());
-    let c = || { let _ = &t; 
+    let c = || {
+        let _ = &t;
         //~^ ERROR: drop order
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t` to be fully captured
@@ -80,7 +83,8 @@ fn test4_only_non_copy_types_need_migration() {
     // `t1` is Copy because all of its elements are Copy
     let t1 = (0i32, 0i32);
 
-    let c = || { let _ = &t; 
+    let c = || {
+        let _ = &t;
         //~^ ERROR: drop order
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t` to be fully captured
@@ -101,7 +105,8 @@ fn test5_only_drop_types_need_migration() {
     // `s` doesn't implement Drop or any elements within it, and doesn't need migration
     let s = S(0i32, 0i32);
 
-    let c = || { let _ = &t; 
+    let c = || {
+        let _ = &t;
         //~^ ERROR: drop order
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t` to be fully captured
@@ -119,7 +124,8 @@ fn test5_only_drop_types_need_migration() {
 fn test6_move_closures_non_copy_types_might_need_migration() {
     let t = (String::new(), String::new());
     let t1 = (String::new(), String::new());
-    let c = move || { let _ = (&t1, &t); 
+    let c = move || {
+        let _ = (&t1, &t);
         //~^ ERROR: drop order
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t1`, `t` to be fully captured
@@ -139,7 +145,8 @@ fn test6_move_closures_non_copy_types_might_need_migration() {
 fn test7_drop_non_drop_aggregate_need_migration() {
     let t = (String::new(), String::new(), 0i32);
 
-    let c = || { let _ = &t; 
+    let c = || {
+        let _ = &t;
         //~^ ERROR: drop order
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t` to be fully captured