use is_unit() and remove redundant From<Ty<I>> on definition of type Term

Author: Jamesbarford

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1531,7 +1531,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             write!(self, "...")?;
         }
         write!(self, ")")?;
-        if !matches!(output.kind(), ty::Tuple(tys) if tys.is_empty()) {
+        if !output.is_unit() {
             write!(self, " -> ")?;
             output.print(self)?;
         }
@@ -2040,7 +2040,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             }
             write!(p, ")")?;
 
-            if !matches!(sig.output().kind(), ty::Tuple(tys) if tys.is_empty()) {
+            if !sig.output().is_unit() {
                 write!(p, " -> ")?;
                 sig.output().print(p)?;
             }

compiler/rustc_type_ir/src/interner.rs

@@ -61,7 +61,7 @@ pub trait Interner:
     type GenericArgs: GenericArgs<Self>;
     type GenericArgsSlice: Copy + Debug + Hash + Eq + SliceLike<Item = Self::GenericArg>;
     type GenericArg: GenericArg<Self>;
-    type Term: Term<Self> + From<Ty<Self>>;
+    type Term: Term<Self>;
 
     type BoundVarKinds: Copy
         + Debug