Remove Clone derive from ImplicitCtxt.

It's unnecessary.

compiler/rustc_interface/src/callbacks.rs

@@ -42,7 +42,7 @@ fn track_diagnostic<R>(diagnostic: DiagInner, f: &mut dyn FnMut(DiagInner) -> R)
             icx.tcx.dep_graph.record_diagnostic(icx.tcx, &diagnostic);
 
             // Diagnostics are tracked, we can ignore the dependency.
-            let icx = tls::ImplicitCtxt { task_deps: TaskDepsRef::Ignore, ..icx.clone() };
+            let icx = tls::ImplicitCtxt { task_deps: TaskDepsRef::Ignore, ..*icx };
             tls::enter_context(&icx, move || (*f)(diagnostic))
         } else {
             // In any other case, invoke diagnostics anyway.

compiler/rustc_middle/src/dep_graph/mod.rs

@@ -63,7 +63,7 @@ fn with_deps<OP, R>(task_deps: TaskDepsRef<'_>, op: OP) -> R
     OP: FnOnce() -> R,
 {
     ty::tls::with_context(|icx| {
-        let icx = ty::tls::ImplicitCtxt { task_deps, ..icx.clone() };
+        let icx = ty::tls::ImplicitCtxt { task_deps, ..*icx };
         ty::tls::enter_context(&icx, op)
     })
 }

compiler/rustc_middle/src/ty/context/tls.rs

@@ -9,7 +9,6 @@
 /// executing a new query. Whenever there's a `TyCtxt` value available
 /// you should also have access to an `ImplicitCtxt` through the functions
 /// in this module.
-#[derive(Clone)]
 pub struct ImplicitCtxt<'a, 'tcx> {
     /// The current `TyCtxt`.
     pub tcx: TyCtxt<'tcx>,

compiler/rustc_query_impl/src/plumbing.rs

@@ -81,7 +81,7 @@ pub(crate) fn start_query<R>(
         let icx = ImplicitCtxt {
             query: Some(job_id),
             query_depth: icx.query_depth + if depth_limit { 1 } else { 0 },
-            ..icx.clone()
+            ..*icx
         };
 
         // Use the `ImplicitCtxt` while we execute the query.