diff options
| -rw-r--r-- | src/librustc_typeck/check/coercion.rs | 7 | ||||
| -rw-r--r-- | src/librustc_typeck/check/demand.rs | 83 | ||||
| -rw-r--r-- | src/librustc_typeck/check/mod.rs | 106 |
3 files changed, 111 insertions, 85 deletions
diff --git a/src/librustc_typeck/check/coercion.rs b/src/librustc_typeck/check/coercion.rs index 6f3cd56c7bf..ac8b639edbf 100644 --- a/src/librustc_typeck/check/coercion.rs +++ b/src/librustc_typeck/check/coercion.rs @@ -1233,7 +1233,12 @@ impl<'gcx, 'tcx, 'exprs, E> CoerceMany<'gcx, 'tcx, 'exprs, E> augment_error(&mut db); } - db.emit(); + if expression.filter(|e| fcx.is_assign_to_bool(e, expected)).is_some() { + // Error reported in `check_assign` so avoid emitting error again. + db.delay_as_bug(); + } else { + db.emit(); + } self.final_ty = Some(fcx.tcx.types.err); } diff --git a/src/librustc_typeck/check/demand.rs b/src/librustc_typeck/check/demand.rs index b1a249d821b..60fa266f0bb 100644 --- a/src/librustc_typeck/check/demand.rs +++ b/src/librustc_typeck/check/demand.rs @@ -119,44 +119,65 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { let expr_ty = self.resolve_type_vars_with_obligations(checked_ty); let mut err = self.report_mismatched_types(&cause, expected, expr_ty, e); - // 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) - if let ty::Adt(expected_adt, substs) = expected.sty { - if expected_adt.is_enum() { - let mut compatible_variants = expected_adt.variants - .iter() - .filter(|variant| variant.fields.len() == 1) - .filter_map(|variant| { - let sole_field = &variant.fields[0]; - let sole_field_ty = sole_field.ty(self.tcx, substs); - if self.can_coerce(expr_ty, sole_field_ty) { - let variant_path = self.tcx.def_path_str(variant.def_id); - // FIXME #56861: DRYer prelude filtering - Some(variant_path.trim_start_matches("std::prelude::v1::").to_string()) - } else { - None - } - }).peekable(); - - if compatible_variants.peek().is_some() { - let expr_text = print::to_string(print::NO_ANN, |s| s.print_expr(expr)); - let suggestions = compatible_variants - .map(|v| format!("{}({})", v, expr_text)); - err.span_suggestions( - expr.span, - "try using a variant of the expected type", - suggestions, - Applicability::MaybeIncorrect, - ); - } - } + if self.is_assign_to_bool(expr, expected) { + // Error reported in `check_assign` so avoid emitting error again. + err.delay_as_bug(); + return (expected, None) } + self.suggest_compatible_variants(&mut err, expr, expected, expr_ty); self.suggest_ref_or_into(&mut err, expr, expected, expr_ty); (expected, Some(err)) } + /// Returns whether the expected type is `bool` and the expression is `x = y`. + pub fn is_assign_to_bool(&self, expr: &hir::Expr, expected: Ty<'tcx>) -> bool { + if let hir::ExprKind::Assign(..) = expr.node { + return expected == self.tcx.types.bool; + } + 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) + fn suggest_compatible_variants( + &self, + err: &mut DiagnosticBuilder<'_>, + expr: &hir::Expr, + expected: Ty<'tcx>, + expr_ty: Ty<'tcx>, + ) { + if let ty::Adt(expected_adt, substs) = expected.sty { + if !expected_adt.is_enum() { + return; + } + + let mut compatible_variants = expected_adt.variants + .iter() + .filter(|variant| variant.fields.len() == 1) + .filter_map(|variant| { + let sole_field = &variant.fields[0]; + let sole_field_ty = sole_field.ty(self.tcx, substs); + if self.can_coerce(expr_ty, sole_field_ty) { + let variant_path = self.tcx.def_path_str(variant.def_id); + // FIXME #56861: DRYer prelude filtering + Some(variant_path.trim_start_matches("std::prelude::v1::").to_string()) + } else { + None + } + }).peekable(); + + if compatible_variants.peek().is_some() { + let expr_text = print::to_string(print::NO_ANN, |s| s.print_expr(expr)); + let suggestions = compatible_variants + .map(|v| format!("{}({})", v, expr_text)); + let msg = "try using a variant of the expected type"; + err.span_suggestions(expr.span, msg, suggestions, Applicability::MaybeIncorrect); + } + } + } + pub fn get_conversion_methods(&self, span: Span, expected: Ty<'tcx>, checked_ty: Ty<'tcx>) -> Vec<AssociatedItem> { let mut methods = self.probe_for_return_type(span, diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs index b11bd9c2408..804fe9c5b5d 100644 --- a/src/librustc_typeck/check/mod.rs +++ b/src/librustc_typeck/check/mod.rs @@ -246,9 +246,6 @@ pub enum Expectation<'tcx> { /// We know nothing about what type this expression should have. NoExpectation, - /// This expression is an `if` condition, it must resolve to `bool`. - ExpectIfCondition, - /// This expression should have the type given (or some subtype). ExpectHasType(Ty<'tcx>), @@ -328,7 +325,6 @@ impl<'a, 'gcx, 'tcx> Expectation<'tcx> { fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> { match self { NoExpectation => NoExpectation, - ExpectIfCondition => ExpectIfCondition, ExpectCastableToType(t) => { ExpectCastableToType(fcx.resolve_type_vars_if_possible(&t)) } @@ -344,7 +340,6 @@ impl<'a, 'gcx, 'tcx> Expectation<'tcx> { fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> { match self.resolve(fcx) { NoExpectation => None, - ExpectIfCondition => Some(fcx.tcx.types.bool), ExpectCastableToType(ty) | ExpectHasType(ty) | ExpectRvalueLikeUnsized(ty) => Some(ty), @@ -358,7 +353,6 @@ impl<'a, 'gcx, 'tcx> Expectation<'tcx> { fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> { match self.resolve(fcx) { ExpectHasType(ty) => Some(ty), - ExpectIfCondition => Some(fcx.tcx.types.bool), NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None, } } @@ -3150,25 +3144,13 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { } if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) { - // Add help to type error if this is an `if` condition with an assignment. - if let (ExpectIfCondition, &ExprKind::Assign(ref lhs, ref rhs)) - = (expected, &expr.node) - { - let msg = "try comparing for equality"; - if let (Ok(left), Ok(right)) = ( - self.tcx.sess.source_map().span_to_snippet(lhs.span), - self.tcx.sess.source_map().span_to_snippet(rhs.span)) - { - err.span_suggestion( - expr.span, - msg, - format!("{} == {}", left, right), - Applicability::MaybeIncorrect); - } else { - err.help(msg); - } + if self.is_assign_to_bool(expr, expected_ty) { + // Error reported in `check_assign` so avoid emitting error again. + // FIXME(centril): Consider removing if/when `if` desugars to `match`. + err.delay_as_bug(); + } else { + err.emit(); } - err.emit(); } ty } @@ -3339,7 +3321,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { opt_else_expr: Option<&'gcx hir::Expr>, sp: Span, expected: Expectation<'tcx>) -> Ty<'tcx> { - let cond_ty = self.check_expr_meets_expectation_or_error(cond_expr, ExpectIfCondition); + let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool); let cond_diverges = self.diverges.get(); self.diverges.set(Diverges::Maybe); @@ -4424,34 +4406,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { tcx.types.never } ExprKind::Assign(ref lhs, ref rhs) => { - let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace); - - let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty); - - match expected { - ExpectIfCondition => { - self.tcx.sess.delay_span_bug(lhs.span, "invalid lhs expression in if;\ - expected error elsehwere"); - } - _ => { - // Only check this if not in an `if` condition, as the - // mistyped comparison help is more appropriate. - if !lhs.is_place_expr() { - struct_span_err!(self.tcx.sess, expr.span, E0070, - "invalid left-hand side expression") - .span_label(expr.span, "left-hand of expression not valid") - .emit(); - } - } - } - - self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized); - - if lhs_ty.references_error() || rhs_ty.references_error() { - tcx.types.err - } else { - tcx.mk_unit() - } + self.check_assign(expr, expected, lhs, rhs) } ExprKind::If(ref cond, ref then_expr, ref opt_else_expr) => { self.check_then_else(&cond, then_expr, opt_else_expr.as_ref().map(|e| &**e), @@ -4752,6 +4707,51 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { } } + /// Type check assignment expression `expr` of form `lhs = rhs`. + /// The expected type is `()` and is passsed to the function for the purposes of diagnostics. + fn check_assign( + &self, + expr: &'gcx hir::Expr, + expected: Expectation<'tcx>, + lhs: &'gcx hir::Expr, + rhs: &'gcx hir::Expr, + ) -> Ty<'tcx> { + let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace); + let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty); + + let expected_ty = expected.coercion_target_type(self, expr.span); + if expected_ty == self.tcx.types.bool { + // The expected type is `bool` but this will result in `()` so we can reasonably + // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`. + // The likely cause of this is `if foo = bar { .. }`. + let actual_ty = self.tcx.mk_unit(); + let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap(); + let msg = "try comparing for equality"; + let left = self.tcx.sess.source_map().span_to_snippet(lhs.span); + let right = self.tcx.sess.source_map().span_to_snippet(rhs.span); + if let (Ok(left), Ok(right)) = (left, right) { + let help = format!("{} == {}", left, right); + err.span_suggestion(expr.span, msg, help, Applicability::MaybeIncorrect); + } else { + err.help(msg); + } + err.emit(); + } else if !lhs.is_place_expr() { + struct_span_err!(self.tcx.sess, expr.span, E0070, + "invalid left-hand side expression") + .span_label(expr.span, "left-hand of expression not valid") + .emit(); + } + + self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized); + + if lhs_ty.references_error() || rhs_ty.references_error() { + self.tcx.types.err + } else { + self.tcx.mk_unit() + } + } + // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary. // The newly resolved definition is written into `type_dependent_defs`. fn finish_resolving_struct_path(&self, |