Introduce Diverges::always constructor

Rename the existing Diverges.always method to Diverges.is_always

Author: Aaron1011

src/librustc_typeck/check/_match.rs

@@ -43,10 +43,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // If there are no arms, that is a diverging match; a special case.
         if arms.is_empty() {
-            self.diverges.set(self.diverges.get() | Diverges::Always {
-                span: expr.span,
-                custom_note: None
-            });
+            self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
             return tcx.types.never;
         }
 
@@ -198,7 +195,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// When the previously checked expression (the scrutinee) diverges,
     /// warn the user about the match arms being unreachable.
     fn warn_arms_when_scrutinee_diverges(&self, arms: &'tcx [hir::Arm], source: hir::MatchSource) {
-        if self.diverges.get().always() {
+        if self.diverges.get().is_always() {
             use hir::MatchSource::*;
             let msg = match source {
                 IfDesugar { .. } | IfLetDesugar { .. } => "block in `if` expression",

src/librustc_typeck/check/expr.rs

@@ -170,10 +170,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Any expression that produces a value of type `!` must have diverged
         if ty.is_never() {
-            self.diverges.set(self.diverges.get() | Diverges::Always {
-                span: expr.span,
-                custom_note: None
-            });
+            self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
         }
 
         // Record the type, which applies it effects.

src/librustc_typeck/check/mod.rs

@@ -470,6 +470,16 @@ pub enum Diverges {
     WarnedAlways
 }
 
+impl Diverges {
+    /// Creates a `Diverges::Always` with the provided span and the default note message
+    fn always(span: Span) -> Diverges {
+        Diverges::Always {
+            span,
+            custom_note: None
+        }
+    }
+}
+
 // Convenience impls for combinig `Diverges`.
 
 impl ops::BitAnd for Diverges {
@@ -499,7 +509,7 @@ impl ops::BitOrAssign for Diverges {
 }
 
 impl Diverges {
-    fn always(self) -> bool {
+    fn is_always(self) -> bool {
         // Enum comparison ignores the
         // contents of fields, so we just
         // fill them in with garbage here.
@@ -3852,7 +3862,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 //
                 // #41425 -- label the implicit `()` as being the
                 // "found type" here, rather than the "expected type".
-                if !self.diverges.get().always() {
+                if !self.diverges.get().is_always() {
                     // #50009 -- Do not point at the entire fn block span, point at the return type
                     // span, as it is the cause of the requirement, and
                     // `consider_hint_about_removing_semicolon` will point at the last expression