From 6289ed842897f75f7b1f06aee44f9f123f57077d Mon Sep 17 00:00:00 2001 From: Gurinder Singh Date: Fri, 19 Apr 2024 18:30:28 +0530 Subject: [PATCH] Remove note about iteration count in coerce and replace it with a simple note suggesting returning a value. The type mismatch error was never due to how many times the loop iterates. It is more because of the peculiar structure of what the for loop desugars to. So the note talking about iteration count didn't make sense --- compiler/rustc_hir_typeck/src/coercion.rs | 155 +-------- compiler/rustc_hir_typeck/src/demand.rs | 3 +- .../src/fn_ctxt/suggestions.rs | 89 +++++- tests/ui/coercion/coerce-loop-issue-122561.rs | 110 +++++++ .../coercion/coerce-loop-issue-122561.stderr | 299 ++++++++++++++++++ .../did_you_mean/compatible-variants.stderr | 3 + .../break-while-condition.stderr | 18 +- tests/ui/issues/issue-27042.stderr | 2 + tests/ui/issues/issue-50585.stderr | 6 + tests/ui/typeck/issue-100285.rs | 4 +- tests/ui/typeck/issue-100285.stderr | 39 +-- tests/ui/typeck/issue-98982.rs | 4 +- tests/ui/typeck/issue-98982.stderr | 18 +- 13 files changed, 545 insertions(+), 205 deletions(-) create mode 100644 tests/ui/coercion/coerce-loop-issue-122561.rs create mode 100644 tests/ui/coercion/coerce-loop-issue-122561.stderr diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs index 4165fa7f07d10..8de9402af2044 100644 --- a/compiler/rustc_hir_typeck/src/coercion.rs +++ b/compiler/rustc_hir_typeck/src/coercion.rs @@ -37,11 +37,9 @@ use crate::errors::SuggestBoxingForReturnImplTrait; use crate::FnCtxt; -use rustc_errors::{codes::*, struct_span_code_err, Applicability, Diag, MultiSpan}; +use rustc_errors::{codes::*, struct_span_code_err, Applicability, Diag}; use rustc_hir as hir; use rustc_hir::def_id::{DefId, LocalDefId}; -use rustc_hir::intravisit::{self, Visitor}; -use rustc_hir::Expr; use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer; use rustc_infer::infer::type_variable::TypeVariableOrigin; use rustc_infer::infer::{Coercion, DefineOpaqueTypes, InferOk, InferResult}; @@ -95,22 +93,6 @@ impl<'a, 'tcx> Deref for Coerce<'a, 'tcx> { type CoerceResult<'tcx> = InferResult<'tcx, (Vec>, Ty<'tcx>)>; -struct CollectRetsVisitor<'tcx> { - ret_exprs: Vec<&'tcx hir::Expr<'tcx>>, -} - -impl<'tcx> Visitor<'tcx> for CollectRetsVisitor<'tcx> { - fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { - match expr.kind { - hir::ExprKind::Ret(_) => self.ret_exprs.push(expr), - // `return` in closures does not return from the outer function - hir::ExprKind::Closure(_) => return, - _ => {} - } - intravisit::walk_expr(self, expr); - } -} - /// Coercing a mutable reference to an immutable works, while /// coercing `&T` to `&mut T` should be forbidden. fn coerce_mutbls<'tcx>( @@ -1601,7 +1583,6 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> { let mut err; let mut unsized_return = false; - let mut visitor = CollectRetsVisitor { ret_exprs: vec![] }; match *cause.code() { ObligationCauseCode::ReturnNoExpression => { err = struct_span_code_err!( @@ -1636,11 +1617,6 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> { if !fcx.tcx.features().unsized_locals { unsized_return = self.is_return_ty_definitely_unsized(fcx); } - if let Some(expression) = expression - && let hir::ExprKind::Loop(loop_blk, ..) = expression.kind - { - intravisit::walk_block(&mut visitor, loop_blk); - } } ObligationCauseCode::ReturnValue(id) => { err = self.report_return_mismatched_types( @@ -1741,6 +1717,22 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> { augment_error(&mut err); if let Some(expr) = expression { + if let hir::ExprKind::Loop( + _, + _, + loop_src @ (hir::LoopSource::While | hir::LoopSource::ForLoop), + _, + ) = expr.kind + { + let loop_type = if loop_src == hir::LoopSource::While { + "`while` loops" + } else { + "`for` loops" + }; + + err.note(format!("{loop_type} evaluate to unit type `()`")); + } + fcx.emit_coerce_suggestions( &mut err, expr, @@ -1749,15 +1741,6 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> { None, Some(coercion_error), ); - if visitor.ret_exprs.len() > 0 { - self.note_unreachable_loop_return( - &mut err, - fcx.tcx, - &expr, - &visitor.ret_exprs, - expected, - ); - } } let reported = err.emit_unless(unsized_return); @@ -1831,110 +1814,6 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> { ); } - fn note_unreachable_loop_return( - &self, - err: &mut Diag<'_>, - tcx: TyCtxt<'tcx>, - expr: &hir::Expr<'tcx>, - ret_exprs: &Vec<&'tcx hir::Expr<'tcx>>, - ty: Ty<'tcx>, - ) { - let hir::ExprKind::Loop(_, _, _, loop_span) = expr.kind else { - return; - }; - let mut span: MultiSpan = vec![loop_span].into(); - span.push_span_label(loop_span, "this might have zero elements to iterate on"); - const MAXITER: usize = 3; - let iter = ret_exprs.iter().take(MAXITER); - for ret_expr in iter { - span.push_span_label( - ret_expr.span, - "if the loop doesn't execute, this value would never get returned", - ); - } - err.span_note( - span, - "the function expects a value to always be returned, but loops might run zero times", - ); - if MAXITER < ret_exprs.len() { - err.note(format!( - "if the loop doesn't execute, {} other values would never get returned", - ret_exprs.len() - MAXITER - )); - } - let hir = tcx.hir(); - let item = hir.get_parent_item(expr.hir_id); - let ret_msg = "return a value for the case when the loop has zero elements to iterate on"; - let ret_ty_msg = - "otherwise consider changing the return type to account for that possibility"; - let node = tcx.hir_node(item.into()); - if let Some(body_id) = node.body_id() - && let Some(sig) = node.fn_sig() - && let hir::ExprKind::Block(block, _) = hir.body(body_id).value.kind - && !ty.is_never() - { - let indentation = if let None = block.expr - && let [.., last] = &block.stmts - { - tcx.sess.source_map().indentation_before(last.span).unwrap_or_else(String::new) - } else if let Some(expr) = block.expr { - tcx.sess.source_map().indentation_before(expr.span).unwrap_or_else(String::new) - } else { - String::new() - }; - if let None = block.expr - && let [.., last] = &block.stmts - { - err.span_suggestion_verbose( - last.span.shrink_to_hi(), - ret_msg, - format!("\n{indentation}/* `{ty}` value */"), - Applicability::MaybeIncorrect, - ); - } else if let Some(expr) = block.expr { - err.span_suggestion_verbose( - expr.span.shrink_to_hi(), - ret_msg, - format!("\n{indentation}/* `{ty}` value */"), - Applicability::MaybeIncorrect, - ); - } - let mut sugg = match sig.decl.output { - hir::FnRetTy::DefaultReturn(span) => { - vec![(span, " -> Option<()>".to_string())] - } - hir::FnRetTy::Return(ty) => { - vec![ - (ty.span.shrink_to_lo(), "Option<".to_string()), - (ty.span.shrink_to_hi(), ">".to_string()), - ] - } - }; - for ret_expr in ret_exprs { - match ret_expr.kind { - hir::ExprKind::Ret(Some(expr)) => { - sugg.push((expr.span.shrink_to_lo(), "Some(".to_string())); - sugg.push((expr.span.shrink_to_hi(), ")".to_string())); - } - hir::ExprKind::Ret(None) => { - sugg.push((ret_expr.span.shrink_to_hi(), " Some(())".to_string())); - } - _ => {} - } - } - if let None = block.expr - && let [.., last] = &block.stmts - { - sugg.push((last.span.shrink_to_hi(), format!("\n{indentation}None"))); - } else if let Some(expr) = block.expr { - sugg.push((expr.span.shrink_to_hi(), format!("\n{indentation}None"))); - } - err.multipart_suggestion(ret_ty_msg, sugg, Applicability::MaybeIncorrect); - } else { - err.help(format!("{ret_msg}, {ret_ty_msg}")); - } - } - fn report_return_mismatched_types<'a>( &self, cause: &ObligationCause<'tcx>, diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs index 618d90a07ec29..60c0b1872fa03 100644 --- a/compiler/rustc_hir_typeck/src/demand.rs +++ b/compiler/rustc_hir_typeck/src/demand.rs @@ -57,7 +57,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { || self.suggest_into(err, expr, expr_ty, expected) || self.suggest_floating_point_literal(err, expr, expected) || self.suggest_null_ptr_for_literal_zero_given_to_ptr_arg(err, expr, expected) - || self.suggest_coercing_result_via_try_operator(err, expr, expected, expr_ty); + || self.suggest_coercing_result_via_try_operator(err, expr, expected, expr_ty) + || self.suggest_returning_value_after_loop(err, expr, expected); if !suggested { self.note_source_of_type_mismatch_constraint( diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs index 133778a416cc2..d00fea4fae498 100644 --- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs +++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs @@ -18,8 +18,8 @@ use rustc_hir::def::Res; use rustc_hir::def::{CtorKind, CtorOf, DefKind}; use rustc_hir::lang_items::LangItem; use rustc_hir::{ - CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind, GenericBound, HirId, Node, - Path, QPath, Stmt, StmtKind, TyKind, WherePredicate, + Arm, CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind, GenericBound, HirId, + Node, Path, QPath, Stmt, StmtKind, TyKind, WherePredicate, }; use rustc_hir_analysis::collect::suggest_impl_trait; use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer; @@ -1942,6 +1942,91 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { false } + // If the expr is a while or for loop and is the tail expr of its + // enclosing body suggest returning a value right after it + pub fn suggest_returning_value_after_loop( + &self, + err: &mut Diag<'_>, + expr: &hir::Expr<'tcx>, + expected: Ty<'tcx>, + ) -> bool { + let hir = self.tcx.hir(); + let enclosing_scope = + hir.get_enclosing_scope(expr.hir_id).map(|hir_id| self.tcx.hir_node(hir_id)); + + // Get tail expr of the enclosing block or body + let tail_expr = if let Some(Node::Block(hir::Block { expr, .. })) = enclosing_scope + && expr.is_some() + { + *expr + } else { + let body_def_id = hir.enclosing_body_owner(expr.hir_id); + let body_id = hir.body_owned_by(body_def_id); + let body = hir.body(body_id); + + // Get tail expr of the body + match body.value.kind { + // Regular function body etc. + hir::ExprKind::Block(block, _) => block.expr, + // Anon const body (there's no block in this case) + hir::ExprKind::DropTemps(expr) => Some(expr), + _ => None, + } + }; + + let Some(tail_expr) = tail_expr else { + return false; // Body doesn't have a tail expr we can compare with + }; + + // Get the loop expr within the tail expr + let loop_expr_in_tail = match expr.kind { + hir::ExprKind::Loop(_, _, hir::LoopSource::While, _) => tail_expr, + hir::ExprKind::Loop(_, _, hir::LoopSource::ForLoop, _) => { + match tail_expr.peel_drop_temps() { + Expr { kind: ExprKind::Match(_, [Arm { body, .. }], _), .. } => body, + _ => return false, // Not really a for loop + } + } + _ => return false, // Not a while or a for loop + }; + + // If the expr is the loop expr in the tail + // then make the suggestion + if expr.hir_id == loop_expr_in_tail.hir_id { + let span = expr.span; + + let (msg, suggestion) = if expected.is_never() { + ( + "consider adding a diverging expression here", + "`loop {}` or `panic!(\"...\")`".to_string(), + ) + } else { + ("consider returning a value here", format!("`{expected}` value")) + }; + + let src_map = self.tcx.sess.source_map(); + let suggestion = if src_map.is_multiline(expr.span) { + let indentation = src_map.indentation_before(span).unwrap_or_else(String::new); + format!("\n{indentation}/* {suggestion} */") + } else { + // If the entire expr is on a single line + // put the suggestion also on the same line + format!(" /* {suggestion} */") + }; + + err.span_suggestion_verbose( + span.shrink_to_hi(), + msg, + suggestion, + Applicability::MaybeIncorrect, + ); + + true + } else { + false + } + } + /// If the expected type is an enum (Issue #55250) with any variants whose /// sole field is of the found type, suggest such variants. (Issue #42764) pub(crate) fn suggest_compatible_variants( diff --git a/tests/ui/coercion/coerce-loop-issue-122561.rs b/tests/ui/coercion/coerce-loop-issue-122561.rs new file mode 100644 index 0000000000000..e08884ad6a4a2 --- /dev/null +++ b/tests/ui/coercion/coerce-loop-issue-122561.rs @@ -0,0 +1,110 @@ +// Regression test for #122561 + +fn for_infinite() -> bool { + for i in 0.. { + //~^ ERROR mismatched types + return false; + } +} + +fn for_finite() -> String { + for i in 0..5 { + //~^ ERROR mismatched types + return String::from("test"); + } +} + +fn for_zero_times() -> bool { + for i in 0..0 { + //~^ ERROR mismatched types + return true; + } +} + +fn for_never_type() -> ! { + for i in 0..5 { + //~^ ERROR mismatched types + } +} + +// Entire function on a single line. +// Tests that we format the suggestion +// correctly in this case +fn for_single_line() -> bool { for i in 0.. { return false; } } +//~^ ERROR mismatched types + +// Loop in an anon const in function args +// Tests that we: +// a. deal properly with this complex case +// b. format the suggestion correctly so +// that it's readable +fn for_in_arg(a: &[(); for x in 0..2 {}]) -> bool { +//~^ ERROR `for` is not allowed in a `const` +//~| ERROR mismatched types + true +} + +fn while_inifinite() -> bool { + while true { + //~^ ERROR mismatched types + //~| WARN denote infinite loops with `loop { ... }` [while_true] + return true; + } +} + +fn while_finite() -> bool { + let mut i = 0; + while i < 3 { + //~^ ERROR mismatched types + i += 1; + return true; + } +} + +fn while_zero_times() -> bool { + while false { + //~^ ERROR mismatched types + return true; + } +} + +fn while_never_type() -> ! { + while true { + //~^ ERROR mismatched types + //~| WARN denote infinite loops with `loop { ... }` [while_true] + } +} + +// No type mismatch error in this case +fn loop_() -> bool { + loop { + return true; + } +} + +const C: i32 = { + for i in 0.. { + //~^ ERROR `for` is not allowed in a `const` + //~| ERROR mismatched types + } +}; + +fn main() { + let _ = [10; { + for i in 0..5 { + //~^ ERROR `for` is not allowed in a `const` + //~| ERROR mismatched types + } + }]; + + let _ = [10; { + while false { + //~^ ERROR mismatched types + } + }]; + + + let _ = |a: &[(); for x in 0..2 {}]| {}; + //~^ ERROR `for` is not allowed in a `const` + //~| ERROR mismatched types +} diff --git a/tests/ui/coercion/coerce-loop-issue-122561.stderr b/tests/ui/coercion/coerce-loop-issue-122561.stderr new file mode 100644 index 0000000000000..0f77fd1364d6b --- /dev/null +++ b/tests/ui/coercion/coerce-loop-issue-122561.stderr @@ -0,0 +1,299 @@ +warning: denote infinite loops with `loop { ... }` + --> $DIR/coerce-loop-issue-122561.rs:48:5 + | +LL | while true { + | ^^^^^^^^^^ help: use `loop` + | + = note: `#[warn(while_true)]` on by default + +warning: denote infinite loops with `loop { ... }` + --> $DIR/coerce-loop-issue-122561.rs:72:5 + | +LL | while true { + | ^^^^^^^^^^ help: use `loop` + +error[E0658]: `for` is not allowed in a `const` + --> $DIR/coerce-loop-issue-122561.rs:41:24 + | +LL | fn for_in_arg(a: &[(); for x in 0..2 {}]) -> bool { + | ^^^^^^^^^^^^^^^^ + | + = note: see issue #87575 for more information + = help: add `#![feature(const_for)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: `for` is not allowed in a `const` + --> $DIR/coerce-loop-issue-122561.rs:86:5 + | +LL | / for i in 0.. { +LL | | +LL | | +LL | | } + | |_____^ + | + = note: see issue #87575 for more information + = help: add `#![feature(const_for)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: `for` is not allowed in a `const` + --> $DIR/coerce-loop-issue-122561.rs:94:9 + | +LL | / for i in 0..5 { +LL | | +LL | | +LL | | } + | |_________^ + | + = note: see issue #87575 for more information + = help: add `#![feature(const_for)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: `for` is not allowed in a `const` + --> $DIR/coerce-loop-issue-122561.rs:107:23 + | +LL | let _ = |a: &[(); for x in 0..2 {}]| {}; + | ^^^^^^^^^^^^^^^^ + | + = note: see issue #87575 for more information + = help: add `#![feature(const_for)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:41:24 + | +LL | fn for_in_arg(a: &[(); for x in 0..2 {}]) -> bool { + | ^^^^^^^^^^^^^^^^ expected `usize`, found `()` + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL | fn for_in_arg(a: &[(); for x in 0..2 {} /* `usize` value */]) -> bool { + | +++++++++++++++++++ + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:86:5 + | +LL | / for i in 0.. { +LL | | +LL | | +LL | | } + | |_____^ expected `i32`, found `()` + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `i32` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:4:5 + | +LL | fn for_infinite() -> bool { + | ---- expected `bool` because of return type +LL | / for i in 0.. { +LL | | +LL | | return false; +LL | | } + | |_____^ expected `bool`, found `()` + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `bool` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:11:5 + | +LL | fn for_finite() -> String { + | ------ expected `String` because of return type +LL | / for i in 0..5 { +LL | | +LL | | return String::from("test"); +LL | | } + | |_____^ expected `String`, found `()` + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `String` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:18:5 + | +LL | fn for_zero_times() -> bool { + | ---- expected `bool` because of return type +LL | / for i in 0..0 { +LL | | +LL | | return true; +LL | | } + | |_____^ expected `bool`, found `()` + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `bool` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:25:5 + | +LL | fn for_never_type() -> ! { + | - expected `!` because of return type +LL | / for i in 0..5 { +LL | | +LL | | } + | |_____^ expected `!`, found `()` + | + = note: expected type `!` + found unit type `()` + = note: `for` loops evaluate to unit type `()` +help: consider adding a diverging expression here + | +LL ~ } +LL + /* `loop {}` or `panic!("...")` */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:33:32 + | +LL | fn for_single_line() -> bool { for i in 0.. { return false; } } + | ---- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `bool`, found `()` + | | + | expected `bool` because of return type + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL | fn for_single_line() -> bool { for i in 0.. { return false; } /* `bool` value */ } + | ++++++++++++++++++ + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:48:5 + | +LL | fn while_inifinite() -> bool { + | ---- expected `bool` because of return type +LL | / while true { +LL | | +LL | | +LL | | return true; +LL | | } + | |_____^ expected `bool`, found `()` + | + = note: `while` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `bool` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:57:5 + | +LL | fn while_finite() -> bool { + | ---- expected `bool` because of return type +LL | let mut i = 0; +LL | / while i < 3 { +LL | | +LL | | i += 1; +LL | | return true; +LL | | } + | |_____^ expected `bool`, found `()` + | + = note: `while` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `bool` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:65:5 + | +LL | fn while_zero_times() -> bool { + | ---- expected `bool` because of return type +LL | / while false { +LL | | +LL | | return true; +LL | | } + | |_____^ expected `bool`, found `()` + | + = note: `while` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `bool` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:72:5 + | +LL | fn while_never_type() -> ! { + | - expected `!` because of return type +LL | / while true { +LL | | +LL | | +LL | | } + | |_____^ expected `!`, found `()` + | + = note: expected type `!` + found unit type `()` + = note: `while` loops evaluate to unit type `()` +help: consider adding a diverging expression here + | +LL ~ } +LL + /* `loop {}` or `panic!("...")` */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:94:9 + | +LL | / for i in 0..5 { +LL | | +LL | | +LL | | } + | |_________^ expected `usize`, found `()` + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `usize` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:101:9 + | +LL | / while false { +LL | | +LL | | } + | |_________^ expected `usize`, found `()` + | + = note: `while` loops evaluate to unit type `()` +help: consider returning a value here + | +LL ~ } +LL + /* `usize` value */ + | + +error[E0308]: mismatched types + --> $DIR/coerce-loop-issue-122561.rs:107:23 + | +LL | let _ = |a: &[(); for x in 0..2 {}]| {}; + | ^^^^^^^^^^^^^^^^ expected `usize`, found `()` + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL | let _ = |a: &[(); for x in 0..2 {} /* `usize` value */]| {}; + | +++++++++++++++++++ + +error: aborting due to 18 previous errors; 2 warnings emitted + +Some errors have detailed explanations: E0308, E0658. +For more information about an error, try `rustc --explain E0308`. diff --git a/tests/ui/did_you_mean/compatible-variants.stderr b/tests/ui/did_you_mean/compatible-variants.stderr index f2bbd8ced8f24..2c75537ca194f 100644 --- a/tests/ui/did_you_mean/compatible-variants.stderr +++ b/tests/ui/did_you_mean/compatible-variants.stderr @@ -11,6 +11,7 @@ LL | | } | = note: expected enum `Option<()>` found unit type `()` + = note: `while` loops evaluate to unit type `()` help: try adding an expression at the end of the block | LL ~ } @@ -49,6 +50,7 @@ LL | | } | = note: expected enum `Option<()>` found unit type `()` + = note: `for` loops evaluate to unit type `()` help: try adding an expression at the end of the block | LL ~ } @@ -106,6 +108,7 @@ LL | while false {} | = note: expected enum `Option<()>` found unit type `()` + = note: `while` loops evaluate to unit type `()` help: try adding an expression at the end of the block | LL ~ while false {} diff --git a/tests/ui/for-loop-while/break-while-condition.stderr b/tests/ui/for-loop-while/break-while-condition.stderr index 48b29f44fa106..07a57424575fd 100644 --- a/tests/ui/for-loop-while/break-while-condition.stderr +++ b/tests/ui/for-loop-while/break-while-condition.stderr @@ -20,6 +20,12 @@ LL | | } | = note: expected type `!` found unit type `()` + = note: `while` loops evaluate to unit type `()` +help: consider adding a diverging expression here + | +LL ~ } +LL + /* `loop {}` or `panic!("...")` */ + | error[E0308]: mismatched types --> $DIR/break-while-condition.rs:24:13 @@ -31,14 +37,12 @@ LL | | } | = note: expected type `!` found unit type `()` -note: the function expects a value to always be returned, but loops might run zero times - --> $DIR/break-while-condition.rs:24:13 + = note: `while` loops evaluate to unit type `()` +help: consider adding a diverging expression here + | +LL ~ } +LL + /* `loop {}` or `panic!("...")` */ | -LL | while false { - | ^^^^^^^^^^^ this might have zero elements to iterate on -LL | return - | ------ if the loop doesn't execute, this value would never get returned - = help: return a value for the case when the loop has zero elements to iterate on, otherwise consider changing the return type to account for that possibility error: aborting due to 3 previous errors diff --git a/tests/ui/issues/issue-27042.stderr b/tests/ui/issues/issue-27042.stderr index ba39399e46eda..6586e61f2f644 100644 --- a/tests/ui/issues/issue-27042.stderr +++ b/tests/ui/issues/issue-27042.stderr @@ -40,6 +40,8 @@ error[E0308]: mismatched types LL | / 'c: LL | | for _ in None { break }; // but here we cite the whole loop | |_______________________________^ expected `i32`, found `()` + | + = note: `for` loops evaluate to unit type `()` error[E0308]: mismatched types --> $DIR/issue-27042.rs:15:9 diff --git a/tests/ui/issues/issue-50585.stderr b/tests/ui/issues/issue-50585.stderr index 13181f1cf7fe4..e7f13e634750c 100644 --- a/tests/ui/issues/issue-50585.stderr +++ b/tests/ui/issues/issue-50585.stderr @@ -13,6 +13,12 @@ error[E0308]: mismatched types | LL | |y: Vec<[(); for x in 0..2 {}]>| {}; | ^^^^^^^^^^^^^^^^ expected `usize`, found `()` + | + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here + | +LL | |y: Vec<[(); for x in 0..2 {} /* `usize` value */]>| {}; + | +++++++++++++++++++ error: aborting due to 2 previous errors diff --git a/tests/ui/typeck/issue-100285.rs b/tests/ui/typeck/issue-100285.rs index 460e0457105f5..bea4b2bc2bbe7 100644 --- a/tests/ui/typeck/issue-100285.rs +++ b/tests/ui/typeck/issue-100285.rs @@ -1,4 +1,4 @@ -fn foo(n: i32) -> i32 { //~ HELP otherwise consider changing the return type to account for that possibility +fn foo(n: i32) -> i32 { for i in 0..0 { //~ ERROR mismatched types [E0308] if n < 0 { return i; @@ -14,7 +14,7 @@ fn foo(n: i32) -> i32 { //~ HELP otherwise consider changing the return type to return 5; } - } //~ HELP return a value for the case when the loop has zero elements to iterate on + } //~ HELP consider returning a value here } fn main() {} diff --git a/tests/ui/typeck/issue-100285.stderr b/tests/ui/typeck/issue-100285.stderr index c0deb63af59ac..6f86fd18e0f68 100644 --- a/tests/ui/typeck/issue-100285.stderr +++ b/tests/ui/typeck/issue-100285.stderr @@ -12,47 +12,12 @@ LL | | LL | | } | |_____^ expected `i32`, found `()` | -note: the function expects a value to always be returned, but loops might run zero times - --> $DIR/issue-100285.rs:2:5 - | -LL | for i in 0..0 { - | ^^^^^^^^^^^^^ this might have zero elements to iterate on -LL | if n < 0 { -LL | return i; - | -------- if the loop doesn't execute, this value would never get returned -LL | } else if n < 10 { -LL | return 1; - | -------- if the loop doesn't execute, this value would never get returned -LL | } else if n < 20 { -LL | return 2; - | -------- if the loop doesn't execute, this value would never get returned - = note: if the loop doesn't execute, 3 other values would never get returned -help: return a value for the case when the loop has zero elements to iterate on + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here | LL ~ } LL ~ /* `i32` value */ | -help: otherwise consider changing the return type to account for that possibility - | -LL ~ fn foo(n: i32) -> Option { -LL | for i in 0..0 { -LL | if n < 0 { -LL ~ return Some(i); -LL | } else if n < 10 { -LL ~ return Some(1); -LL | } else if n < 20 { -LL ~ return Some(2); -LL | } else if n < 30 { -LL ~ return Some(3); -LL | } else if n < 40 { -LL ~ return Some(4); -LL | } else { -LL ~ return Some(5); -LL | } -LL | -LL ~ } -LL ~ None - | error: aborting due to 1 previous error diff --git a/tests/ui/typeck/issue-98982.rs b/tests/ui/typeck/issue-98982.rs index f875d20fa4c53..3eff9fbe360b7 100644 --- a/tests/ui/typeck/issue-98982.rs +++ b/tests/ui/typeck/issue-98982.rs @@ -1,7 +1,7 @@ -fn foo() -> i32 { //~ HELP otherwise consider changing the return type to account for that possibility +fn foo() -> i32 { for i in 0..0 { //~ ERROR mismatched types [E0308] return i; - } //~ HELP return a value for the case when the loop has zero elements to iterate on + } //~ HELP consider returning a value here } fn main() {} diff --git a/tests/ui/typeck/issue-98982.stderr b/tests/ui/typeck/issue-98982.stderr index d8d5a86b157f2..3d40ff4d5afbe 100644 --- a/tests/ui/typeck/issue-98982.stderr +++ b/tests/ui/typeck/issue-98982.stderr @@ -8,26 +8,12 @@ LL | | return i; LL | | } | |_____^ expected `i32`, found `()` | -note: the function expects a value to always be returned, but loops might run zero times - --> $DIR/issue-98982.rs:2:5 - | -LL | for i in 0..0 { - | ^^^^^^^^^^^^^ this might have zero elements to iterate on -LL | return i; - | -------- if the loop doesn't execute, this value would never get returned -help: return a value for the case when the loop has zero elements to iterate on + = note: `for` loops evaluate to unit type `()` +help: consider returning a value here | LL ~ } LL ~ /* `i32` value */ | -help: otherwise consider changing the return type to account for that possibility - | -LL ~ fn foo() -> Option { -LL | for i in 0..0 { -LL ~ return Some(i); -LL ~ } -LL ~ None - | error: aborting due to 1 previous error