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| 1 | +impl<'tcx> TypeErrCtxt<'_, 'tcx> { |
| 2 | + fn note_error_origin( |
| 3 | + &self, |
| 4 | + err: &mut Diagnostic, |
| 5 | + cause: &ObligationCause<'tcx>, |
| 6 | + exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>, |
| 7 | + terr: TypeError<'tcx>, |
| 8 | + ) { |
| 9 | + match *cause.code() { |
| 10 | + ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => { |
| 11 | + let ty = self.resolve_vars_if_possible(root_ty); |
| 12 | + if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_))) |
| 13 | + { |
| 14 | + // don't show type `_` |
| 15 | + if span.desugaring_kind() == Some(DesugaringKind::ForLoop) |
| 16 | + && let ty::Adt(def, substs) = ty.kind() |
| 17 | + && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option) |
| 18 | + { |
| 19 | + err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0))); |
| 20 | + } else { |
| 21 | + err.span_label(span, format!("this expression has type `{}`", ty)); |
| 22 | + } |
| 23 | + } |
| 24 | + if let Some(ty::error::ExpectedFound { found, .. }) = exp_found |
| 25 | + && ty.is_box() && ty.boxed_ty() == found |
| 26 | + && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) |
| 27 | + { |
| 28 | + err.span_suggestion( |
| 29 | + span, |
| 30 | + "consider dereferencing the boxed value", |
| 31 | + format!("*{}", snippet), |
| 32 | + Applicability::MachineApplicable, |
| 33 | + ); |
| 34 | + } |
| 35 | + } |
| 36 | + ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => { |
| 37 | + err.span_label(span, "expected due to this"); |
| 38 | + } |
| 39 | + ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause { |
| 40 | + arm_block_id, |
| 41 | + arm_span, |
| 42 | + arm_ty, |
| 43 | + prior_arm_block_id, |
| 44 | + prior_arm_span, |
| 45 | + prior_arm_ty, |
| 46 | + source, |
| 47 | + ref prior_arms, |
| 48 | + scrut_hir_id, |
| 49 | + opt_suggest_box_span, |
| 50 | + scrut_span, |
| 51 | + .. |
| 52 | + }) => match source { |
| 53 | + hir::MatchSource::TryDesugar => { |
| 54 | + if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found { |
| 55 | + let scrut_expr = self.tcx.hir().expect_expr(scrut_hir_id); |
| 56 | + let scrut_ty = if let hir::ExprKind::Call(_, args) = &scrut_expr.kind { |
| 57 | + let arg_expr = args.first().expect("try desugaring call w/out arg"); |
| 58 | + self.typeck_results.as_ref().and_then(|typeck_results| { |
| 59 | + typeck_results.expr_ty_opt(arg_expr) |
| 60 | + }) |
| 61 | + } else { |
| 62 | + bug!("try desugaring w/out call expr as scrutinee"); |
| 63 | + }; |
| 64 | + |
| 65 | + match scrut_ty { |
| 66 | + Some(ty) if expected == ty => { |
| 67 | + let source_map = self.tcx.sess.source_map(); |
| 68 | + err.span_suggestion( |
| 69 | + source_map.end_point(cause.span), |
| 70 | + "try removing this `?`", |
| 71 | + "", |
| 72 | + Applicability::MachineApplicable, |
| 73 | + ); |
| 74 | + } |
| 75 | + _ => {} |
| 76 | + } |
| 77 | + } |
| 78 | + } |
| 79 | + _ => { |
| 80 | + // `prior_arm_ty` can be `!`, `expected` will have better info when present. |
| 81 | + let t = self.resolve_vars_if_possible(match exp_found { |
| 82 | + Some(ty::error::ExpectedFound { expected, .. }) => expected, |
| 83 | + _ => prior_arm_ty, |
| 84 | + }); |
| 85 | + let source_map = self.tcx.sess.source_map(); |
| 86 | + let mut any_multiline_arm = source_map.is_multiline(arm_span); |
| 87 | + if prior_arms.len() <= 4 { |
| 88 | + for sp in prior_arms { |
| 89 | + any_multiline_arm |= source_map.is_multiline(*sp); |
| 90 | + err.span_label(*sp, format!("this is found to be of type `{}`", t)); |
| 91 | + } |
| 92 | + } else if let Some(sp) = prior_arms.last() { |
| 93 | + any_multiline_arm |= source_map.is_multiline(*sp); |
| 94 | + err.span_label( |
| 95 | + *sp, |
| 96 | + format!("this and all prior arms are found to be of type `{}`", t), |
| 97 | + ); |
| 98 | + } |
| 99 | + let outer_error_span = if any_multiline_arm { |
| 100 | + // Cover just `match` and the scrutinee expression, not |
| 101 | + // the entire match body, to reduce diagram noise. |
| 102 | + cause.span.shrink_to_lo().to(scrut_span) |
| 103 | + } else { |
| 104 | + cause.span |
| 105 | + }; |
| 106 | + let msg = "`match` arms have incompatible types"; |
| 107 | + err.span_label(outer_error_span, msg); |
| 108 | + self.suggest_remove_semi_or_return_binding( |
| 109 | + err, |
| 110 | + prior_arm_block_id, |
| 111 | + prior_arm_ty, |
| 112 | + prior_arm_span, |
| 113 | + arm_block_id, |
| 114 | + arm_ty, |
| 115 | + arm_span, |
| 116 | + ); |
| 117 | + if let Some(ret_sp) = opt_suggest_box_span { |
| 118 | + // Get return type span and point to it. |
| 119 | + self.suggest_boxing_for_return_impl_trait( |
| 120 | + err, |
| 121 | + ret_sp, |
| 122 | + prior_arms.iter().chain(std::iter::once(&arm_span)).map(|s| *s), |
| 123 | + ); |
| 124 | + } |
| 125 | + } |
| 126 | + }, |
| 127 | + ObligationCauseCode::IfExpression(box IfExpressionCause { |
| 128 | + then_id, |
| 129 | + else_id, |
| 130 | + then_ty, |
| 131 | + else_ty, |
| 132 | + outer_span, |
| 133 | + opt_suggest_box_span, |
| 134 | + }) => { |
| 135 | + let then_span = self.find_block_span_from_hir_id(then_id); |
| 136 | + let else_span = self.find_block_span_from_hir_id(else_id); |
| 137 | + err.span_label(then_span, "expected because of this"); |
| 138 | + if let Some(sp) = outer_span { |
| 139 | + err.span_label(sp, "`if` and `else` have incompatible types"); |
| 140 | + } |
| 141 | + self.suggest_remove_semi_or_return_binding( |
| 142 | + err, |
| 143 | + Some(then_id), |
| 144 | + then_ty, |
| 145 | + then_span, |
| 146 | + Some(else_id), |
| 147 | + else_ty, |
| 148 | + else_span, |
| 149 | + ); |
| 150 | + if let Some(ret_sp) = opt_suggest_box_span { |
| 151 | + self.suggest_boxing_for_return_impl_trait( |
| 152 | + err, |
| 153 | + ret_sp, |
| 154 | + [then_span, else_span].into_iter(), |
| 155 | + ); |
| 156 | + } |
| 157 | + } |
| 158 | + ObligationCauseCode::LetElse => { |
| 159 | + err.help("try adding a diverging expression, such as `return` or `panic!(..)`"); |
| 160 | + err.help("...or use `match` instead of `let...else`"); |
| 161 | + } |
| 162 | + _ => { |
| 163 | + if let ObligationCauseCode::BindingObligation(_, span) |
| 164 | + | ObligationCauseCode::ExprBindingObligation(_, span, ..) |
| 165 | + = cause.code().peel_derives() |
| 166 | + && let TypeError::RegionsPlaceholderMismatch = terr |
| 167 | + { |
| 168 | + err.span_note( * span, |
| 169 | + "the lifetime requirement is introduced here"); |
| 170 | + } |
| 171 | + } |
| 172 | + } |
| 173 | + } |
| 174 | +} |
| 175 | + |
| 176 | +impl<'tcx> InferCtxt<'tcx> { |
| 177 | + /// Given a [`hir::Block`], get the span of its last expression or |
| 178 | + /// statement, peeling off any inner blocks. |
| 179 | + pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span { |
| 180 | + let block = block.innermost_block(); |
| 181 | + if let Some(expr) = &block.expr { |
| 182 | + expr.span |
| 183 | + } else if let Some(stmt) = block.stmts.last() { |
| 184 | + // possibly incorrect trailing `;` in the else arm |
| 185 | + stmt.span |
| 186 | + } else { |
| 187 | + // empty block; point at its entirety |
| 188 | + block.span |
| 189 | + } |
| 190 | + } |
| 191 | + |
| 192 | + /// Given a [`hir::HirId`] for a block, get the span of its last expression |
| 193 | + /// or statement, peeling off any inner blocks. |
| 194 | + pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span { |
| 195 | + match self.tcx.hir().get(hir_id) { |
| 196 | + hir::Node::Block(blk) => self.find_block_span(blk), |
| 197 | + // The parser was in a weird state if either of these happen, but |
| 198 | + // it's better not to panic. |
| 199 | + hir::Node::Expr(e) => e.span, |
| 200 | + _ => rustc_span::DUMMY_SP, |
| 201 | + } |
| 202 | + } |
| 203 | +} |
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