src/librustc/infer/error_reporting/nice_region_error/different_lifetimes.rs

   1 //! Error Reporting for Anonymous Region Lifetime Errors
   2 //! where both the regions are anonymous.
   3
   4 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
   5 use crate::infer::error_reporting::nice_region_error::util::AnonymousParamInfo;
   6 use crate::util::common::ErrorReported;
   7
   8 use rustc_error_codes::*;
   9
  10 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
  11     /// Print the error message for lifetime errors when both the concerned regions are anonymous.
  12     ///
  13     /// Consider a case where we have
  14     ///
  15     /// ```no_run
  16     /// fn foo(x: &mut Vec<&u8>, y: &u8) {
  17     ///     x.push(y);
  18     /// }
  19     /// ```
  20     ///
  21     /// The example gives
  22     ///
  23     /// ```text
  24     /// fn foo(x: &mut Vec<&u8>, y: &u8) {
  25     ///                    ---      --- these references are declared with different lifetimes...
  26     ///     x.push(y);
  27     ///     ^ ...but data from `y` flows into `x` here
  28     /// ```
  29     ///
  30     /// It has been extended for the case of structs too.
  31     ///
  32     /// Consider the example
  33     ///
  34     /// ```no_run
  35     /// struct Ref<'a> { x: &'a u32 }
  36     /// ```
  37     ///
  38     /// ```text
  39     /// fn foo(mut x: Vec<Ref>, y: Ref) {
  40     ///                   ---      --- these structs are declared with different lifetimes...
  41     ///     x.push(y);
  42     ///     ^ ...but data from `y` flows into `x` here
  43     /// }
  44     /// ```
  45     ///
  46     /// It will later be extended to trait objects.
  47     pub(super) fn try_report_anon_anon_conflict(&self) -> Option<ErrorReported> {
  48         let (span, sub, sup) = self.regions();
  49
  50         // Determine whether the sub and sup consist of both anonymous (elided) regions.
  51         let anon_reg_sup = self.tcx().is_suitable_region(sup)?;
  52
  53         let anon_reg_sub = self.tcx().is_suitable_region(sub)?;
  54         let scope_def_id_sup = anon_reg_sup.def_id;
  55         let bregion_sup = anon_reg_sup.boundregion;
  56         let scope_def_id_sub = anon_reg_sub.def_id;
  57         let bregion_sub = anon_reg_sub.boundregion;
  58
  59         let ty_sup = self.find_anon_type(sup, &bregion_sup)?;
  60
  61         let ty_sub = self.find_anon_type(sub, &bregion_sub)?;
  62
  63         debug!(
  64             "try_report_anon_anon_conflict: found_param1={:?} sup={:?} br1={:?}",
  65             ty_sub,
  66             sup,
  67             bregion_sup
  68         );
  69         debug!(
  70             "try_report_anon_anon_conflict: found_param2={:?} sub={:?} br2={:?}",
  71             ty_sup,
  72             sub,
  73             bregion_sub
  74         );
  75
  76         let (ty_sup, ty_fndecl_sup) = ty_sup;
  77         let (ty_sub, ty_fndecl_sub) = ty_sub;
  78
  79         let AnonymousParamInfo {
  80             param: anon_param_sup, ..
  81         } = self.find_param_with_region(sup, sup)?;
  82         let AnonymousParamInfo {
  83             param: anon_param_sub, ..
  84         } = self.find_param_with_region(sub, sub)?;
  85
  86         let sup_is_ret_type =
  87             self.is_return_type_anon(scope_def_id_sup, bregion_sup, ty_fndecl_sup);
  88         let sub_is_ret_type =
  89             self.is_return_type_anon(scope_def_id_sub, bregion_sub, ty_fndecl_sub);
  90
  91         let span_label_var1 = match anon_param_sup.pat.simple_ident() {
  92             Some(simple_ident) => format!(" from `{}`", simple_ident),
  93             None => String::new(),
  94         };
  95
  96         let span_label_var2 = match anon_param_sub.pat.simple_ident() {
  97             Some(simple_ident) => format!(" into `{}`", simple_ident),
  98             None => String::new(),
  99         };
 100
 101         let (span_1, span_2, main_label, span_label) = match (sup_is_ret_type, sub_is_ret_type) {
 102             (None, None) => {
 103                 let (main_label_1, span_label_1) = if ty_sup.hir_id == ty_sub.hir_id {
 104                     (
 105                         "this type is declared with multiple lifetimes...".to_owned(),
 106                         "...but data with one lifetime flows into the other here".to_owned()
 107                     )
 108                 } else {
 109                     (
 110                         "these two types are declared with different lifetimes...".to_owned(),
 111                         format!(
 112                             "...but data{} flows{} here",
 113                             span_label_var1,
 114                             span_label_var2
 115                         ),
 116                     )
 117                 };
 118                 (ty_sup.span, ty_sub.span, main_label_1, span_label_1)
 119             }
 120
 121             (Some(ret_span), _) => (
 122                 ty_sub.span,
 123                 ret_span,
 124                 "this parameter and the return type are declared \
 125                  with different lifetimes...".to_owned()
 126                 ,
 127                 format!("...but data{} is returned here", span_label_var1),
 128             ),
 129             (_, Some(ret_span)) => (
 130                 ty_sup.span,
 131                 ret_span,
 132                 "this parameter and the return type are declared \
 133                  with different lifetimes...".to_owned()
 134                 ,
 135                 format!("...but data{} is returned here", span_label_var1),
 136             ),
 137         };
 138
 139
 140         struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch")
 141             .span_label(span_1, main_label)
 142             .span_label(span_2, String::new())
 143             .span_label(span, span_label)
 144             .emit();
 145         return Some(ErrorReported);
 146     }
 147 }