Fix some comments

compiler/rustc_abi/src/lib.rs

@@ -1806,7 +1806,7 @@ pub struct PointeeInfo {
     pub safe: Option<PointerKind>,
     /// If `safe` is `Some`, then the pointer is either null or dereferenceable for this many bytes.
     /// On a function argument, "dereferenceable" here means "dereferenceable for the entire duration
-    /// of this function call", i.e. it is UB for the memory that this pointer points to to be freed
+    /// of this function call", i.e. it is UB for the memory that this pointer points to be freed
     /// while this function is still running.
     /// The size can be zero if the pointer is not dereferenceable.
     pub size: Size,

compiler/rustc_hir_typeck/src/pat.rs

@@ -2640,7 +2640,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         detailed_label: &str,
     ) {
         // Try to trim the span we're labeling to just the `&` or binding mode that's an issue.
-        // If the subpattern's span is is from an expansion, the emitted label will not be trimmed.
+        // If the subpattern's span is from an expansion, the emitted label will not be trimmed.
         let source_map = self.tcx.sess.source_map();
         let cutoff_span = source_map
             .span_extend_prev_while(cutoff_span, char::is_whitespace)

compiler/rustc_middle/src/mir/syntax.rs

@@ -74,7 +74,7 @@ pub enum MirPhase {
     ///  - Unwinding: in analysis MIR, unwinding from a function which may not unwind aborts. In runtime
     ///    MIR, this is UB.
     ///  - Retags: If `-Zmir-emit-retag` is enabled, analysis MIR has "implicit" retags in the same way
-    ///    that Rust itself has them. Where exactly these are is generally subject to change, and so we
+    ///    that Rust itself has them. Where exactly these are generally subject to change, and so we
     ///    don't document this here. Runtime MIR has most retags explicit (though implicit retags
     ///    can still occur at `Rvalue::{Ref,AddrOf}`).
     ///  - Coroutine bodies: In analysis MIR, locals may actually be behind a pointer that user code has

src/doc/rustc-dev-guide/src/solve/opaque-types.md

@@ -33,7 +33,7 @@ For opaque types in the defining scope and in the implicit-negative coherence mo
 always done in two steps. Outside of the defining scope `normalizes-to` for opaques always
 returns `Err(NoSolution)`.
 
-We start by trying to to assign the expected type as a hidden type.
+We start by trying to assign the expected type as a hidden type.
 
 In the implicit-negative coherence mode, this currently always results in ambiguity without
 interacting with the opaque types storage. We could instead add allow 'defining' all opaque types,