if $c:expr { Some($r:expr) } else { None } =>> $c.then(|| $r)

compiler/rustc_mir_build/src/build/expr/into.rs

@@ -319,7 +319,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 // See the notes for `ExprKind::Array` in `as_rvalue` and for
                 // `ExprKind::Borrow` above.
                 let is_union = adt_def.is_union();
-                let active_field_index = if is_union { Some(fields[0].name.index()) } else { None };
+                let active_field_index = is_union.then(|| fields[0].name.index());
 
                 let scope = this.local_scope();
 

compiler/rustc_mir_build/src/build/matches/test.rs

@@ -563,14 +563,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let not_contained =
                     self.values_not_contained_in_range(&*range, options).unwrap_or(false);
 
-                if not_contained {
+                not_contained.then(|| {
                     // No switch values are contained in the pattern range,
                     // so the pattern can be matched only if this test fails.
-                    let otherwise = options.len();
-                    Some(otherwise)
-                } else {
-                    None
-                }
+                    options.len()
+                })
             }
 
             (&TestKind::SwitchInt { .. }, _) => None,

compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs

@@ -172,7 +172,7 @@ impl IntRange {
         ty: Ty<'tcx>,
         end: &RangeEnd,
     ) -> Option<IntRange> {
-        if Self::is_integral(ty) {
+        Self::is_integral(ty).then(|| {
             // Perform a shift if the underlying types are signed,
             // which makes the interval arithmetic simpler.
             let bias = IntRange::signed_bias(tcx, ty);
@@ -182,10 +182,8 @@ impl IntRange {
                 // This should have been caught earlier by E0030.
                 bug!("malformed range pattern: {}..={}", lo, (hi - offset));
             }
-            Some(IntRange { range: lo..=(hi - offset), bias })
-        } else {
-            None
-        }
+            IntRange { range: lo..=(hi - offset), bias }
+        })
     }
 
     // The return value of `signed_bias` should be XORed with an endpoint to encode/decode it.

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -203,11 +203,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                 if !lower_overflow && !higher_overflow {
                     self.tcx.sess.emit_err(LowerRangeBoundMustBeLessThanOrEqualToUpper {
                         span,
-                        teach: if self.tcx.sess.teach(&error_code!(E0030)) {
-                            Some(())
-                        } else {
-                            None
-                        },
+                        teach: self.tcx.sess.teach(&error_code!(E0030)).then(|| ()),
                     });
                 }
                 PatKind::Wild