diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs index 14e5d2ae62337..0520c9ac60cf0 100644 --- a/compiler/rustc_ast_passes/src/ast_validation.rs +++ b/compiler/rustc_ast_passes/src/ast_validation.rs @@ -1463,10 +1463,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> { if let GenericBound::Trait(ref poly, modify) = *bound { match (ctxt, modify) { (BoundKind::SuperTraits, TraitBoundModifier::Maybe) => { - let mut err = self.err_handler().struct_span_err( - poly.span, - &format!("`?Trait` is not permitted in supertraits"), - ); + let mut err = self + .err_handler() + .struct_span_err(poly.span, "`?Trait` is not permitted in supertraits"); let path_str = pprust::path_to_string(&poly.trait_ref.path); err.note(&format!("traits are `?{}` by default", path_str)); err.emit(); @@ -1474,7 +1473,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> { (BoundKind::TraitObject, TraitBoundModifier::Maybe) => { let mut err = self.err_handler().struct_span_err( poly.span, - &format!("`?Trait` is not permitted in trait object types"), + "`?Trait` is not permitted in trait object types", ); err.emit(); } diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs index f2b5c83c5c1d0..6478a104815b6 100644 --- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs +++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs @@ -450,10 +450,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> { _ => None, }; - if defined_hir.is_some() { + if let Some(def_hir) = defined_hir { let upvars_map = self.infcx.tcx.upvars_mentioned(def_id).unwrap(); - let upvar_def_span = self.infcx.tcx.hir().span(defined_hir.unwrap()); - let upvar_span = upvars_map.get(&defined_hir.unwrap()).unwrap().span; + let upvar_def_span = self.infcx.tcx.hir().span(def_hir); + let upvar_span = upvars_map.get(&def_hir).unwrap().span; diag.span_label(upvar_def_span, "variable defined here"); diag.span_label(upvar_span, "variable captured here"); } diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs index b6a7bcae93284..3185b952ab886 100644 --- a/compiler/rustc_codegen_ssa/src/mir/place.rs +++ b/compiler/rustc_codegen_ssa/src/mir/place.rs @@ -462,7 +462,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { } }; for elem in place_ref.projection[base..].iter() { - cg_base = match elem.clone() { + cg_base = match *elem { mir::ProjectionElem::Deref => { // a box with a non-zst allocator should not be directly dereferenced if cg_base.layout.ty.is_box() && !cg_base.layout.field(cx, 1).is_zst() { diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs index 4c84bd090cb50..0c954ac6e5f6e 100644 --- a/compiler/rustc_const_eval/src/interpret/eval_context.rs +++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs @@ -520,13 +520,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { frame .instance .try_subst_mir_and_normalize_erasing_regions(*self.tcx, self.param_env, value) - .or_else(|e| { + .map_err(|e| { self.tcx.sess.delay_span_bug( self.cur_span(), format!("failed to normalize {}", e.get_type_for_failure()).as_str(), ); - Err(InterpError::InvalidProgram(InvalidProgramInfo::TooGeneric)) + InterpError::InvalidProgram(InvalidProgramInfo::TooGeneric) }) } @@ -1009,11 +1009,7 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> std::fmt::Debug } } - write!( - fmt, - ": {:?}", - self.ecx.dump_allocs(allocs.into_iter().filter_map(|x| x).collect()) - ) + write!(fmt, ": {:?}", self.ecx.dump_allocs(allocs.into_iter().flatten().collect())) } Place::Ptr(mplace) => match mplace.ptr.provenance.and_then(Provenance::get_alloc_id) { Some(alloc_id) => write!( diff --git a/compiler/rustc_log/src/lib.rs b/compiler/rustc_log/src/lib.rs index c152815eeca68..f2ec80b0c1b63 100644 --- a/compiler/rustc_log/src/lib.rs +++ b/compiler/rustc_log/src/lib.rs @@ -69,13 +69,7 @@ pub fn init_env_logger(env: &str) -> Result<(), Error> { let verbose_entry_exit = match env::var_os(String::from(env) + "_ENTRY_EXIT") { None => false, - Some(v) => { - if &v == "0" { - false - } else { - true - } - } + Some(v) => &v != "0", }; let layer = tracing_tree::HierarchicalLayer::default() diff --git a/compiler/rustc_middle/src/mir/patch.rs b/compiler/rustc_middle/src/mir/patch.rs index 1bc53d3c9f1c5..c1e1cfef9f89d 100644 --- a/compiler/rustc_middle/src/mir/patch.rs +++ b/compiler/rustc_middle/src/mir/patch.rs @@ -167,8 +167,7 @@ impl<'tcx> MirPatch<'tcx> { if loc.statement_index > body[loc.block].statements.len() { let term = body[loc.block].terminator(); for i in term.successors() { - stmts_and_targets - .push((Statement { source_info, kind: stmt.clone() }, i.clone())); + stmts_and_targets.push((Statement { source_info, kind: stmt.clone() }, i)); } delta += 1; continue; diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/build/expr/into.rs index 569012e152b30..ccbb518e72d08 100644 --- a/compiler/rustc_mir_build/src/build/expr/into.rs +++ b/compiler/rustc_mir_build/src/build/expr/into.rs @@ -435,11 +435,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> { } thir::InlineAsmOperand::SymFn { value, span } => { mir::InlineAsmOperand::SymFn { - value: Box::new(Constant { - span, - user_ty: None, - literal: value.into(), - }), + value: Box::new(Constant { span, user_ty: None, literal: value }), } } thir::InlineAsmOperand::SymStatic { def_id } => { diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs index c15b3db1caae3..3774a39503521 100644 --- a/compiler/rustc_mir_build/src/build/matches/test.rs +++ b/compiler/rustc_mir_build/src/build/matches/test.rs @@ -264,7 +264,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> { ); } else if let [success, fail] = *make_target_blocks(self) { assert_eq!(value.ty(), ty); - let expect = self.literal_operand(test.span, value.into()); + let expect = self.literal_operand(test.span, value); let val = Operand::Copy(place); self.compare(block, success, fail, source_info, BinOp::Eq, expect, val); } else { @@ -277,8 +277,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> { let target_blocks = make_target_blocks(self); // Test `val` by computing `lo <= val && val <= hi`, using primitive comparisons. - let lo = self.literal_operand(test.span, lo.into()); - let hi = self.literal_operand(test.span, hi.into()); + let lo = self.literal_operand(test.span, lo); + let hi = self.literal_operand(test.span, hi); let val = Operand::Copy(place); let [success, fail] = *target_blocks else { @@ -370,7 +370,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> { place: Place<'tcx>, mut ty: Ty<'tcx>, ) { - let mut expect = self.literal_operand(source_info.span, value.into()); + let mut expect = self.literal_operand(source_info.span, value); let mut val = Operand::Copy(place); // If we're using `b"..."` as a pattern, we need to insert an diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs b/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs index a02d8c89772a2..82e1ae9d274c0 100644 --- a/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs +++ b/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs @@ -845,7 +845,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { let first_provided_ty = if let Some((ty, _)) = final_arg_types[input_idx] { format!(",found `{}`", ty) } else { - "".into() + String::new() }; labels.push(( first_span, @@ -857,7 +857,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { if let Some((ty, _)) = final_arg_types[other_input_idx] { format!(",found `{}`", ty) } else { - "".into() + String::new() }; labels.push(( second_span, @@ -875,7 +875,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { let provided_ty = if let Some((ty, _)) = final_arg_types[dst_arg] { format!(",found `{}`", ty) } else { - "".into() + String::new() }; labels.push(( provided_args[dst_arg].span, @@ -1744,8 +1744,7 @@ fn label_fn_like<'tcx>( .get_if_local(def_id) .and_then(|node| node.body_id()) .into_iter() - .map(|id| tcx.hir().body(id).params) - .flatten(); + .flat_map(|id| tcx.hir().body(id).params); for param in params { spans.push_span_label(param.span, String::new()); diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs index f9c0ea82e02f1..4e54d554c6ec2 100644 --- a/compiler/rustc_typeck/src/check/method/suggest.rs +++ b/compiler/rustc_typeck/src/check/method/suggest.rs @@ -492,7 +492,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { Obligation { cause: cause.clone(), param_env: self.param_env, - predicate: predicate.clone(), + predicate: *predicate, recursion_depth: 0, }, )); @@ -676,7 +676,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { let span = self_ty.span.ctxt().outer_expn_data().call_site; let mut spans: MultiSpan = span.into(); spans.push_span_label(span, derive_msg.to_string()); - let entry = spanned_predicates.entry(spans.into()); + let entry = spanned_predicates.entry(spans); entry.or_insert_with(|| (path, tr_self_ty, Vec::new())).2.push(p); } @@ -704,7 +704,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { ident.span.into() }; spans.push_span_label(ident.span, "in this trait".to_string()); - let entry = spanned_predicates.entry(spans.into()); + let entry = spanned_predicates.entry(spans); entry.or_insert_with(|| (path, tr_self_ty, Vec::new())).2.push(p); } @@ -748,7 +748,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } spans.push_span_label(self_ty.span, String::new()); - let entry = spanned_predicates.entry(spans.into()); + let entry = spanned_predicates.entry(spans); entry.or_insert_with(|| (path, tr_self_ty, Vec::new())).2.push(p); } _ => {} @@ -1460,7 +1460,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { { derives.push(( self_name.clone(), - self_span.clone(), + self_span, parent_diagnostic_name.to_string(), )); } diff --git a/compiler/rustc_typeck/src/check/op.rs b/compiler/rustc_typeck/src/check/op.rs index c99d9d8f9230d..637f6459525a2 100644 --- a/compiler/rustc_typeck/src/check/op.rs +++ b/compiler/rustc_typeck/src/check/op.rs @@ -705,7 +705,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { let predicates = errors .iter() .filter_map(|error| { - error.obligation.predicate.clone().to_opt_poly_trait_pred() + error.obligation.predicate.to_opt_poly_trait_pred() }); for pred in predicates { self.infcx.suggest_restricting_param_bound( diff --git a/library/core/src/option.rs b/library/core/src/option.rs index d0746698f4013..28ea45ed235dc 100644 --- a/library/core/src/option.rs +++ b/library/core/src/option.rs @@ -708,6 +708,26 @@ impl Option { /// let x: Option<&str> = None; /// x.expect("fruits are healthy"); // panics with `fruits are healthy` /// ``` + /// + /// # Recommended Message Style + /// + /// We recommend that `expect` messages are used to describe the reason you + /// _expect_ the `Option` should be `Some`. + /// + /// ```should_panic + /// # let slice: &[u8] = &[]; + /// let item = slice.get(0) + /// .expect("slice should not be empty"); + /// ``` + /// + /// **Hint**: If you're having trouble remembering how to phrase expect + /// error messages remember to focus on the word "should" as in "env + /// variable should be set by blah" or "the given binary should be available + /// and executable by the current user". + /// + /// For more detail on expect message styles and the reasoning behind our + /// recommendation please refer to the section on ["Common Message + /// Styles"](../../std/error/index.html#common-message-styles) in the [`std::error`](../../std/error/index.html) module docs. #[inline] #[track_caller] #[stable(feature = "rust1", since = "1.0.0")] diff --git a/library/core/src/result.rs b/library/core/src/result.rs index 5e5f8a5ab9543..c4dc34fff97fa 100644 --- a/library/core/src/result.rs +++ b/library/core/src/result.rs @@ -1023,6 +1023,26 @@ impl Result { /// let x: Result = Err("emergency failure"); /// x.expect("Testing expect"); // panics with `Testing expect: emergency failure` /// ``` + /// + /// # Recommended Message Style + /// + /// We recommend that `expect` messages are used to describe the reason you + /// _expect_ the `Result` should be `Ok`. + /// + /// ```should_panic + /// let path = std::env::var("IMPORTANT_PATH") + /// .expect("env variable `IMPORTANT_PATH` should be set by `wrapper_script.sh`"); + /// ``` + /// + /// **Hint**: If you're having trouble remembering how to phrase expect + /// error messages remember to focus on the word "should" as in "env + /// variable should be set by blah" or "the given binary should be available + /// and executable by the current user". + /// + /// For more detail on expect message styles and the reasoning behind our recommendation please + /// refer to the section on ["Common Message + /// Styles"](../../std/error/index.html#common-message-styles) in the + /// [`std::error`](../../std/error/index.html) module docs. #[inline] #[track_caller] #[stable(feature = "result_expect", since = "1.4.0")] diff --git a/library/std/src/error.rs b/library/std/src/error.rs index 438304e1664cb..c2d30616019c7 100644 --- a/library/std/src/error.rs +++ b/library/std/src/error.rs @@ -1,4 +1,140 @@ -//! Traits for working with Errors. +//! Interfaces for working with Errors. +//! +//! # Error Handling In Rust +//! +//! The Rust language provides two complementary systems for constructing / +//! representing, reporting, propagating, reacting to, and discarding errors. +//! These responsibilities are collectively known as "error handling." The +//! components of the first system, the panic runtime and interfaces, are most +//! commonly used to represent bugs that have been detected in your program. The +//! components of the second system, `Result`, the error traits, and user +//! defined types, are used to represent anticipated runtime failure modes of +//! your program. +//! +//! ## The Panic Interfaces +//! +//! The following are the primary interfaces of the panic system and the +//! responsibilities they cover: +//! +//! * [`panic!`] and [`panic_any`] (Constructing, Propagated automatically) +//! * [`PanicInfo`] (Reporting) +//! * [`set_hook`], [`take_hook`], and [`#[panic_handler]`][panic-handler] (Reporting) +//! * [`catch_unwind`] and [`resume_unwind`] (Discarding, Propagating) +//! +//! The following are the primary interfaces of the error system and the +//! responsibilities they cover: +//! +//! * [`Result`] (Propagating, Reacting) +//! * The [`Error`] trait (Reporting) +//! * User defined types (Constructing / Representing) +//! * [`match`] and [`downcast`] (Reacting) +//! * The question mark operator ([`?`]) (Propagating) +//! * The partially stable [`Try`] traits (Propagating, Constructing) +//! * [`Termination`] (Reporting) +//! +//! ## Converting Errors into Panics +//! +//! The panic and error systems are not entirely distinct. Often times errors +//! that are anticipated runtime failures in an API might instead represent bugs +//! to a caller. For these situations the standard library provides APIs for +//! constructing panics with an `Error` as it's source. +//! +//! * [`Result::unwrap`] +//! * [`Result::expect`] +//! +//! These functions are equivalent, they either return the inner value if the +//! `Result` is `Ok` or panic if the `Result` is `Err` printing the inner error +//! as the source. The only difference between them is that with `expect` you +//! provide a panic error message to be printed alongside the source, whereas +//! `unwrap` has a default message indicating only that you unwraped an `Err`. +//! +//! Of the two, `expect` is generally preferred since its `msg` field allows you +//! to convey your intent and assumptions which makes tracking down the source +//! of a panic easier. `unwrap` on the other hand can still be a good fit in +//! situations where you can trivially show that a piece of code will never +//! panick, such as `"127.0.0.1".parse::().unwrap()` or early +//! prototyping. +//! +//! # Common Message Styles +//! +//! There are two common styles for how people word `expect` messages. Using +//! the message to present information to users encountering a panic +//! ("expect as error message") or using the message to present information +//! to developers debugging the panic ("expect as precondition"). +//! +//! In the former case the expect message is used to describe the error that +//! has occurred which is considered a bug. Consider the following example: +//! +//! ```should_panic +//! // Read environment variable, panic if it is not present +//! let path = std::env::var("IMPORTANT_PATH").unwrap(); +//! ``` +//! +//! In the "expect as error message" style we would use expect to describe +//! that the environment variable was not set when it should have been: +//! +//! ```should_panic +//! let path = std::env::var("IMPORTANT_PATH") +//! .expect("env variable `IMPORTANT_PATH` is not set"); +//! ``` +//! +//! In the "expect as precondition" style, we would instead describe the +//! reason we _expect_ the `Result` should be `Ok`. With this style we would +//! prefer to write: +//! +//! ```should_panic +//! let path = std::env::var("IMPORTANT_PATH") +//! .expect("env variable `IMPORTANT_PATH` should be set by `wrapper_script.sh`"); +//! ``` +//! +//! The "expect as error message" style does not work as well with the +//! default output of the std panic hooks, and often ends up repeating +//! information that is already communicated by the source error being +//! unwrapped: +//! +//! ```text +//! thread 'main' panicked at 'env variable `IMPORTANT_PATH` is not set: NotPresent', src/main.rs:4:6 +//! ``` +//! +//! In this example we end up mentioning that an env variable is not set, +//! followed by our source message that says the env is not present, the +//! only additional information we're communicating is the name of the +//! environment variable being checked. +//! +//! The "expect as precondition" style instead focuses on source code +//! readability, making it easier to understand what must have gone wrong in +//! situations where panics are being used to represent bugs exclusively. +//! Also, by framing our expect in terms of what "SHOULD" have happened to +//! prevent the source error, we end up introducing new information that is +//! independent from our source error. +//! +//! ```text +//! thread 'main' panicked at 'env variable `IMPORTANT_PATH` should be set by `wrapper_script.sh`: NotPresent', src/main.rs:4:6 +//! ``` +//! +//! In this example we are communicating not only the name of the +//! environment variable that should have been set, but also an explanation +//! for why it should have been set, and we let the source error display as +//! a clear contradiction to our expectation. +//! +//! **Hint**: If you're having trouble remembering how to phrase +//! expect-as-precondition style error messages remember to focus on the word +//! "should" as in "env variable should be set by blah" or "the given binary +//! should be available and executable by the current user". +//! +//! [`panic_any`]: crate::panic::panic_any +//! [`PanicInfo`]: crate::panic::PanicInfo +//! [`catch_unwind`]: crate::panic::catch_unwind +//! [`resume_unwind`]: crate::panic::resume_unwind +//! [`downcast`]: crate::error::Error +//! [`Termination`]: crate::process::Termination +//! [`Try`]: crate::ops::Try +//! [panic hook]: crate::panic::set_hook +//! [`set_hook`]: crate::panic::set_hook +//! [`take_hook`]: crate::panic::take_hook +//! [panic-handler]: +//! [`match`]: ../../std/keyword.match.html +//! [`?`]: ../../std/result/index.html#the-question-mark-operator- #![stable(feature = "rust1", since = "1.0.0")]