Auto merge of #57580 - Centril:rollup, r=Centril

Rollup of 4 pull requests

Successful merges:

 - #56874 (Simplify foreign type rendering.)
 - #57113 (Move diagnostics out from QueryJob and optimize for the case with no diagnostics)
 - #57366 (Point at match discriminant on type error in match arm pattern)
 - #57538 (librustc_mir: Fix ICE with slice patterns)

Failed merges:

 - #57381 (Tweak output of type mismatch between "then" and `else` `if` arms)

r? @ghost

Author: bors

src/librustc/dep_graph/graph.rs

@@ -696,7 +696,7 @@ impl DepGraph {
 
                 // Promote the previous diagnostics to the current session.
                 tcx.queries.on_disk_cache
-                   .store_diagnostics(dep_node_index, diagnostics.clone());
+                   .store_diagnostics(dep_node_index, diagnostics.clone().into());
 
                 for diagnostic in diagnostics {
                     DiagnosticBuilder::new_diagnostic(handle, diagnostic).emit();

src/librustc/infer/error_reporting/mod.rs

@@ -487,6 +487,11 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
     fn note_error_origin(&self, err: &mut DiagnosticBuilder<'tcx>, cause: &ObligationCause<'tcx>) {
         match cause.code {
+            ObligationCauseCode::MatchExpressionArmPattern { span, ty } => {
+                if ty.is_suggestable() {  // don't show type `_`
+                    err.span_label(span, format!("this match expression has type `{}`", ty));
+                }
+            }
             ObligationCauseCode::MatchExpressionArm { arm_span, source } => match source {
                 hir::MatchSource::IfLetDesugar { .. } => {
                     let msg = "`if let` arm with an incompatible type";