Don't store thir::Pat in error structs

In several cases this avoids the need to clone the underlying pattern, and then
print the clone later.

Author: Zalathar

compiler/rustc_middle/src/thir.rs

@@ -9,7 +9,6 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/thir.html
 
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
-use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{BindingMode, ByRef, HirId, MatchSource, RangeEnd};
@@ -702,12 +701,6 @@ impl<'tcx> Pat<'tcx> {
     }
 }
 
-impl<'tcx> IntoDiagArg for Pat<'tcx> {
-    fn into_diag_arg(self) -> DiagArgValue {
-        format!("{self}").into_diag_arg()
-    }
-}
-
 #[derive(Clone, Debug, HashStable, TypeVisitable)]
 pub struct Ascription<'tcx> {
     pub annotation: CanonicalUserTypeAnnotation<'tcx>,

compiler/rustc_mir_build/src/errors.rs

@@ -856,7 +856,7 @@ pub(crate) struct PatternNotCovered<'s, 'tcx> {
     pub(crate) span: Span,
     pub(crate) origin: &'s str,
     #[subdiagnostic]
-    pub(crate) uncovered: Uncovered<'tcx>,
+    pub(crate) uncovered: Uncovered,
     #[subdiagnostic]
     pub(crate) inform: Option<Inform>,
     #[subdiagnostic]

compiler/rustc_pattern_analysis/src/errors.rs

@@ -1,45 +1,44 @@
 use rustc_errors::{Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic};
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
-use rustc_middle::thir::Pat;
 use rustc_middle::ty::Ty;
 use rustc_span::Span;
 
 use crate::rustc::{RustcPatCtxt, WitnessPat};
 
 #[derive(Subdiagnostic)]
 #[label(pattern_analysis_uncovered)]
-pub struct Uncovered<'tcx> {
+pub struct Uncovered {
     #[primary_span]
     span: Span,
     count: usize,
-    witness_1: Pat<'tcx>,
-    witness_2: Pat<'tcx>,
-    witness_3: Pat<'tcx>,
+    witness_1: String, // a printed pattern
+    witness_2: String, // a printed pattern
+    witness_3: String, // a printed pattern
     remainder: usize,
 }
 
-impl<'tcx> Uncovered<'tcx> {
-    pub fn new<'p>(
+impl Uncovered {
+    pub fn new<'p, 'tcx>(
         span: Span,
         cx: &RustcPatCtxt<'p, 'tcx>,
         witnesses: Vec<WitnessPat<'p, 'tcx>>,
     ) -> Self
     where
         'tcx: 'p,
     {
-        let witness_1 = cx.hoist_witness_pat(witnesses.get(0).unwrap());
+        let witness_1 = cx.hoist_witness_pat(witnesses.get(0).unwrap()).to_string();
         Self {
             span,
             count: witnesses.len(),
             // Substitute dummy values if witnesses is smaller than 3. These will never be read.
             witness_2: witnesses
                 .get(1)
-                .map(|w| cx.hoist_witness_pat(w))
-                .unwrap_or_else(|| witness_1.clone()),
+                .map(|w| cx.hoist_witness_pat(w).to_string())
+                .unwrap_or_default(),
             witness_3: witnesses
                 .get(2)
-                .map(|w| cx.hoist_witness_pat(w))
-                .unwrap_or_else(|| witness_1.clone()),
+                .map(|w| cx.hoist_witness_pat(w).to_string())
+                .unwrap_or_default(),
             witness_1,
             remainder: witnesses.len().saturating_sub(3),
         }
@@ -49,19 +48,19 @@ impl<'tcx> Uncovered<'tcx> {
 #[derive(LintDiagnostic)]
 #[diag(pattern_analysis_overlapping_range_endpoints)]
 #[note]
-pub struct OverlappingRangeEndpoints<'tcx> {
+pub struct OverlappingRangeEndpoints {
     #[label]
     pub range: Span,
     #[subdiagnostic]
-    pub overlap: Vec<Overlap<'tcx>>,
+    pub overlap: Vec<Overlap>,
 }
 
-pub struct Overlap<'tcx> {
+pub struct Overlap {
     pub span: Span,
-    pub range: Pat<'tcx>,
+    pub range: String, // a printed pattern
 }
 
-impl<'tcx> Subdiagnostic for Overlap<'tcx> {
+impl Subdiagnostic for Overlap {
     fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
@@ -78,38 +77,38 @@ impl<'tcx> Subdiagnostic for Overlap<'tcx> {
 
 #[derive(LintDiagnostic)]
 #[diag(pattern_analysis_excluside_range_missing_max)]
-pub struct ExclusiveRangeMissingMax<'tcx> {
+pub struct ExclusiveRangeMissingMax {
     #[label]
     #[suggestion(code = "{suggestion}", applicability = "maybe-incorrect")]
     /// This is an exclusive range that looks like `lo..max` (i.e. doesn't match `max`).
     pub first_range: Span,
     /// Suggest `lo..=max` instead.
     pub suggestion: String,
-    pub max: Pat<'tcx>,
+    pub max: String, // a printed pattern
 }
 
 #[derive(LintDiagnostic)]
 #[diag(pattern_analysis_excluside_range_missing_gap)]
-pub struct ExclusiveRangeMissingGap<'tcx> {
+pub struct ExclusiveRangeMissingGap {
     #[label]
     #[suggestion(code = "{suggestion}", applicability = "maybe-incorrect")]
     /// This is an exclusive range that looks like `lo..gap` (i.e. doesn't match `gap`).
     pub first_range: Span,
-    pub gap: Pat<'tcx>,
+    pub gap: String, // a printed pattern
     /// Suggest `lo..=gap` instead.
     pub suggestion: String,
     #[subdiagnostic]
     /// All these ranges skipped over `gap` which we think is probably a mistake.
-    pub gap_with: Vec<GappedRange<'tcx>>,
+    pub gap_with: Vec<GappedRange>,
 }
 
-pub struct GappedRange<'tcx> {
+pub struct GappedRange {
     pub span: Span,
-    pub gap: Pat<'tcx>,
-    pub first_range: Pat<'tcx>,
+    pub gap: String,         // a printed pattern
+    pub first_range: String, // a printed pattern
 }
 
-impl<'tcx> Subdiagnostic for GappedRange<'tcx> {
+impl Subdiagnostic for GappedRange {
     fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
@@ -134,7 +133,7 @@ impl<'tcx> Subdiagnostic for GappedRange<'tcx> {
 pub(crate) struct NonExhaustiveOmittedPattern<'tcx> {
     pub scrut_ty: Ty<'tcx>,
     #[subdiagnostic]
-    pub uncovered: Uncovered<'tcx>,
+    pub uncovered: Uncovered,
 }
 
 #[derive(LintDiagnostic)]

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -966,7 +966,7 @@ impl<'p, 'tcx: 'p> PatCx for RustcPatCtxt<'p, 'tcx> {
         let overlaps: Vec<_> = overlaps_with
             .iter()
             .map(|pat| pat.data().span)
-            .map(|span| errors::Overlap { range: overlap_as_pat.clone(), span })
+            .map(|span| errors::Overlap { range: overlap_as_pat.to_string(), span })
             .collect();
         let pat_span = pat.data().span;
         self.tcx.emit_node_span_lint(
@@ -1014,7 +1014,7 @@ impl<'p, 'tcx: 'p> PatCx for RustcPatCtxt<'p, 'tcx> {
                     // Point at this range.
                     first_range: thir_pat.span,
                     // That's the gap that isn't covered.
-                    max: gap_as_pat.clone(),
+                    max: gap_as_pat.to_string(),
                     // Suggest `lo..=max` instead.
                     suggestion: suggested_range.to_string(),
                 },
@@ -1028,7 +1028,7 @@ impl<'p, 'tcx: 'p> PatCx for RustcPatCtxt<'p, 'tcx> {
                     // Point at this range.
                     first_range: thir_pat.span,
                     // That's the gap that isn't covered.
-                    gap: gap_as_pat.clone(),
+                    gap: gap_as_pat.to_string(),
                     // Suggest `lo..=gap` instead.
                     suggestion: suggested_range.to_string(),
                     // All these ranges skipped over `gap` which we think is probably a
@@ -1037,8 +1037,8 @@ impl<'p, 'tcx: 'p> PatCx for RustcPatCtxt<'p, 'tcx> {
                         .iter()
                         .map(|pat| errors::GappedRange {
                             span: pat.data().span,
-                            gap: gap_as_pat.clone(),
-                            first_range: thir_pat.clone(),
+                            gap: gap_as_pat.to_string(),
+                            first_range: thir_pat.to_string(),
                         })
                         .collect(),
                 },