Auto merge of #52332 - zackmdavis:dead_code_lint_should_say_2_electric_boogaloo, r=pnkfelix

dead-code lint: say "constructed" for structs

Respectively.

This is a sequel to November 2017's #46103 / 1a9dc2e9. It had been
reported (more than once—at least #19140, #44083, and #44565) that the
"never used" language was confusing for enum variants that were "used"
as match patterns, so the wording was changed to say never "constructed"
specifically for enum variants. More recently, the same issue was raised
for structs (#52325). It seems consistent to say "constructed" here,
too, for the same reasons.

~~While we're here, we can also use more specific word "called" for unused
functions and methods. (We declined to do this in #46103, but the
rationale given in the commit message doesn't actually make sense.)~~

This resolves #52325.

7 files changed, 14 insertions, 10 deletions

diff --git a/src/librustc/middle/dead.rs b/src/librustc/middle/dead.rs
index e4fc1b09fce..0f889549b58 100644
--- a/src/librustc/middle/dead.rs
+++ b/src/librustc/middle/dead.rs
@@ -554,12 +554,16 @@ impl<'a, 'tcx> Visitor<'tcx> for DeadVisitor<'a, 'tcx> {
                 hir::ItemKind::Impl(..) => self.tcx.sess.codemap().def_span(item.span),
                 _ => item.span,
             };
+            let participle = match item.node {
+                hir::ItemKind::Struct(..) => "constructed", // Issue #52325
+                _ => "used"
+            };
             self.warn_dead_code(
                 item.id,
                 span,
                 item.name,
                 item.node.descriptive_variant(),
-                "used",
+                participle,
             );
         } else {
             // Only continue if we didn't warn
diff --git a/src/test/compile-fail/lint-dead-code-1.rs b/src/test/compile-fail/lint-dead-code-1.rs
index d6ca5e6b1d9..2fe72365bab 100644
--- a/src/test/compile-fail/lint-dead-code-1.rs
+++ b/src/test/compile-fail/lint-dead-code-1.rs
@@ -19,7 +19,7 @@
 pub use foo2::Bar2;
 
 mod foo {
-    pub struct Bar; //~ ERROR: struct is never used
+    pub struct Bar; //~ ERROR: struct is never constructed
 }
 
 mod foo2 {
@@ -42,7 +42,7 @@ const CONST_USED_IN_ENUM_DISCRIMINANT: isize = 11;
 
 pub type typ = *const UsedStruct4;
 pub struct PubStruct;
-struct PrivStruct; //~ ERROR: struct is never used
+struct PrivStruct; //~ ERROR: struct is never constructed
 struct UsedStruct1 {
     #[allow(dead_code)]
     x: isize
diff --git a/src/test/compile-fail/lint-dead-code-3.rs b/src/test/compile-fail/lint-dead-code-3.rs
index f680e395449..112d3630952 100644
--- a/src/test/compile-fail/lint-dead-code-3.rs
+++ b/src/test/compile-fail/lint-dead-code-3.rs
@@ -20,7 +20,7 @@ extern {
     pub fn extern_foo();
 }
 
-struct Foo; //~ ERROR: struct is never used
+struct Foo; //~ ERROR: struct is never constructed
 impl Foo {
     fn foo(&self) { //~ ERROR: method is never used
         bar()
diff --git a/src/test/ui/span/macro-span-replacement.rs b/src/test/ui/span/macro-span-replacement.rs
index 4fe35042300..7374f157468 100644
--- a/src/test/ui/span/macro-span-replacement.rs
+++ b/src/test/ui/span/macro-span-replacement.rs
@@ -14,7 +14,7 @@
 
 macro_rules! m {
     ($a:tt $b:tt) => {
-        $b $a; //~ WARN struct is never used
+        $b $a; //~ WARN struct is never constructed
     }
 }
 
diff --git a/src/test/ui/span/macro-span-replacement.stderr b/src/test/ui/span/macro-span-replacement.stderr
index bb59fa206df..b12ca86d3c9 100644
--- a/src/test/ui/span/macro-span-replacement.stderr
+++ b/src/test/ui/span/macro-span-replacement.stderr
@@ -1,7 +1,7 @@
-warning: struct is never used: `S`
+warning: struct is never constructed: `S`
   --> $DIR/macro-span-replacement.rs:17:14
    |
-LL |         $b $a; //~ WARN struct is never used
+LL |         $b $a; //~ WARN struct is never constructed
    |              ^
 ...
 LL |     m!(S struct);
diff --git a/src/test/ui/span/unused-warning-point-at-signature.rs b/src/test/ui/span/unused-warning-point-at-signature.rs
index 6a7071d49ae..c074f03db46 100644
--- a/src/test/ui/span/unused-warning-point-at-signature.rs
+++ b/src/test/ui/span/unused-warning-point-at-signature.rs
@@ -19,7 +19,7 @@ enum Enum { //~ WARN enum is never used
     D,
 }
 
-struct Struct { //~ WARN struct is never used
+struct Struct { //~ WARN struct is never constructed
     a: usize,
     b: usize,
     c: usize,
diff --git a/src/test/ui/span/unused-warning-point-at-signature.stderr b/src/test/ui/span/unused-warning-point-at-signature.stderr
index de234344d84..8344853d6de 100644
--- a/src/test/ui/span/unused-warning-point-at-signature.stderr
+++ b/src/test/ui/span/unused-warning-point-at-signature.stderr
@@ -11,10 +11,10 @@ LL | #![warn(unused)]
    |         ^^^^^^
    = note: #[warn(dead_code)] implied by #[warn(unused)]
 
-warning: struct is never used: `Struct`
+warning: struct is never constructed: `Struct`
   --> $DIR/unused-warning-point-at-signature.rs:22:1
    |
-LL | struct Struct { //~ WARN struct is never used
+LL | struct Struct { //~ WARN struct is never constructed
    | ^^^^^^^^^^^^^
 
 warning: function is never used: `func`