Rollup merge of #79877 - bstrie:depinfut, r=oli-obk

Allow `since="TBD"` for rustc_deprecated

Closes #78381.

This PR only affects `#[rustc_deprecated]`, not `#[deprecated]`, so there is no effect on any stable language feature.

Likewise this PR only implements `since="TBD"`, it does not actually tag any library functions with it, so there is no effect on any stable API.

Overview of changes:

* `rustc_middle/stability.rs`:
    * change `deprecation_in_effect` function to return `false` when `since="TBD"`
    * tidy up the compiler output when a deprecated item has `since="TBD"`
* `rustc_passes/stability.rs`:
    * allow `since="TBD"` to pass the sanity check for stable_version < deprecated_version
    * refactor the "invalid stability version" and "invalid deprecation version" error into separate errors
* rustdoc: make `since="TBD"` message on a deprecated item's page match the command-line deprecation output
* tests:
    * test rustdoc output
    * test that the `deprecated_in_future` lint fires when `since="TBD"`
    * test the new "invalid deprecation version" error message

compiler/rustc_middle/src/middle/stability.rs

@@ -132,37 +132,37 @@ pub fn report_unstable(
 /// Checks whether an item marked with `deprecated(since="X")` is currently
 /// deprecated (i.e., whether X is not greater than the current rustc version).
 pub fn deprecation_in_effect(is_since_rustc_version: bool, since: Option<&str>) -> bool {
-    let since = if let Some(since) = since {
-        if is_since_rustc_version {
-            since
-        } else {
-            // We assume that the deprecation is in effect if it's not a
-            // rustc version.
-            return true;
-        }
-    } else {
-        // If since attribute is not set, then we're definitely in effect.
-        return true;
-    };
     fn parse_version(ver: &str) -> Vec<u32> {
         // We ignore non-integer components of the version (e.g., "nightly").
         ver.split(|c| c == '.' || c == '-').flat_map(|s| s.parse()).collect()
     }
 
-    if let Some(rustc) = option_env!("CFG_RELEASE") {
-        let since: Vec<u32> = parse_version(&since);
-        let rustc: Vec<u32> = parse_version(rustc);
-        // We simply treat invalid `since` attributes as relating to a previous
-        // Rust version, thus always displaying the warning.
-        if since.len() != 3 {
-            return true;
-        }
-        since <= rustc
-    } else {
-        // By default, a deprecation warning applies to
-        // the current version of the compiler.
-        true
+    if !is_since_rustc_version {
+        // The `since` field doesn't have semantic purpose in the stable `deprecated`
+        // attribute, only in `rustc_deprecated`.
+        return true;
     }
+
+    if let Some(since) = since {
+        if since == "TBD" {
+            return false;
+        }
+
+        if let Some(rustc) = option_env!("CFG_RELEASE") {
+            let since: Vec<u32> = parse_version(&since);
+            let rustc: Vec<u32> = parse_version(rustc);
+            // We simply treat invalid `since` attributes as relating to a previous
+            // Rust version, thus always displaying the warning.
+            if since.len() != 3 {
+                return true;
+            }
+            return since <= rustc;
+        }
+    };
+
+    // Assume deprecation is in effect if "since" field is missing
+    // or if we can't determine the current Rust version.
+    true
 }
 
 pub fn deprecation_suggestion(
@@ -182,19 +182,24 @@ pub fn deprecation_suggestion(
 }
 
 pub fn deprecation_message(depr: &Deprecation, kind: &str, path: &str) -> (String, &'static Lint) {
-    let (message, lint) = if deprecation_in_effect(
-        depr.is_since_rustc_version,
-        depr.since.map(Symbol::as_str).as_deref(),
-    ) {
+    let since = depr.since.map(Symbol::as_str);
+    let (message, lint) = if deprecation_in_effect(depr.is_since_rustc_version, since.as_deref()) {
         (format!("use of deprecated {} `{}`", kind, path), DEPRECATED)
     } else {
         (
-            format!(
-                "use of {} `{}` that will be deprecated in future version {}",
-                kind,
-                path,
-                depr.since.unwrap()
-            ),
+            if since.as_deref() == Some("TBD") {
+                format!(
+                    "use of {} `{}` that will be deprecated in a future Rust version",
+                    kind, path
+                )
+            } else {
+                format!(
+                    "use of {} `{}` that will be deprecated in future version {}",
+                    kind,
+                    path,
+                    since.unwrap()
+                )
+            },
             DEPRECATED_IN_FUTURE,
         )
     };

compiler/rustc_passes/src/stability.rs

@@ -182,28 +182,32 @@ fn annotate<F>(
                 for (dep_v, stab_v) in
                     dep_since.as_str().split('.').zip(stab_since.as_str().split('.'))
                 {
-                    if let (Ok(dep_v), Ok(stab_v)) = (dep_v.parse::<u64>(), stab_v.parse()) {
-                        match dep_v.cmp(&stab_v) {
-                            Ordering::Less => {
-                                self.tcx.sess.span_err(
-                                    item_sp,
-                                    "An API can't be stabilized \
-                                                                 after it is deprecated",
-                                );
+                    match stab_v.parse::<u64>() {
+                        Err(_) => {
+                            self.tcx.sess.span_err(item_sp, "Invalid stability version found");
+                            break;
+                        }
+                        Ok(stab_vp) => match dep_v.parse::<u64>() {
+                            Ok(dep_vp) => match dep_vp.cmp(&stab_vp) {
+                                Ordering::Less => {
+                                    self.tcx.sess.span_err(
+                                        item_sp,
+                                        "An API can't be stabilized after it is deprecated",
+                                    );
+                                    break;
+                                }
+                                Ordering::Equal => continue,
+                                Ordering::Greater => break,
+                            },
+                            Err(_) => {
+                                if dep_v != "TBD" {
+                                    self.tcx
+                                        .sess
+                                        .span_err(item_sp, "Invalid deprecation version found");
+                                }
                                 break;
                             }
-                            Ordering::Equal => continue,
-                            Ordering::Greater => break,
-                        }
-                    } else {
-                        // Act like it isn't less because the question is now nonsensical,
-                        // and this makes us not do anything else interesting.
-                        self.tcx.sess.span_err(
-                            item_sp,
-                            "Invalid stability or deprecation \
-                                                         version found",
-                        );
-                        break;
+                        },
                     }
                 }
             }

src/librustdoc/html/render/mod.rs

@@ -2279,7 +2279,11 @@ fn short_item_info(item: &clean::Item, cx: &Context, parent: Option<&clean::Item
         let mut message = if let Some(since) = since {
             let since = &since.as_str();
             if !stability::deprecation_in_effect(is_since_rustc_version, Some(since)) {
-                format!("Deprecating in {}", Escape(since))
+                if *since == "TBD" {
+                    format!("Deprecating in a future Rust version")
+                } else {
+                    format!("Deprecating in {}", Escape(since))
+                }
             } else {
                 format!("Deprecated since {}", Escape(since))
             }

src/test/rustdoc/rustc_deprecated-future.rs

@@ -4,8 +4,16 @@
 
 // @has rustc_deprecated_future/index.html '//*[@class="stab deprecated"]' \
 //      'Deprecation planned'
-// @has rustc_deprecated_future/struct.S.html '//*[@class="stab deprecated"]' \
+// @has rustc_deprecated_future/struct.S1.html '//*[@class="stab deprecated"]' \
 //      'Deprecating in 99.99.99: effectively never'
 #[rustc_deprecated(since = "99.99.99", reason = "effectively never")]
 #[stable(feature = "rustc_deprecated-future-test", since = "1.0.0")]
-pub struct S;
+pub struct S1;
+
+// @has rustc_deprecated_future/index.html '//*[@class="stab deprecated"]' \
+//      'Deprecation planned'
+// @has rustc_deprecated_future/struct.S2.html '//*[@class="stab deprecated"]' \
+//      'Deprecating in a future Rust version: literally never'
+#[rustc_deprecated(since = "TBD", reason = "literally never")]
+#[stable(feature = "rustc_deprecated-future-test", since = "1.0.0")]
+pub struct S2;

src/test/ui/deprecation/rustc_deprecation-in-future.rs

@@ -8,8 +8,13 @@
 
 #[rustc_deprecated(since = "99.99.99", reason = "effectively never")]
 #[stable(feature = "rustc_deprecation-in-future-test", since = "1.0.0")]
-pub struct S;
+pub struct S1;
+
+#[rustc_deprecated(since = "TBD", reason = "literally never")]
+#[stable(feature = "rustc_deprecation-in-future-test", since = "1.0.0")]
+pub struct S2;
 
 fn main() {
-    let _ = S; //~ ERROR use of unit struct `S` that will be deprecated in future version 99.99.99: effectively never
+    let _ = S1; //~ ERROR use of unit struct `S1` that will be deprecated in future version 99.99.99: effectively never
+    let _ = S2; //~ ERROR use of unit struct `S2` that will be deprecated in a future Rust version: literally never
 }

src/test/ui/deprecation/rustc_deprecation-in-future.stderr

@@ -1,8 +1,8 @@
-error: use of unit struct `S` that will be deprecated in future version 99.99.99: effectively never
-  --> $DIR/rustc_deprecation-in-future.rs:14:13
+error: use of unit struct `S1` that will be deprecated in future version 99.99.99: effectively never
+  --> $DIR/rustc_deprecation-in-future.rs:18:13
    |
-LL |     let _ = S;
-   |             ^
+LL |     let _ = S1;
+   |             ^^
    |
 note: the lint level is defined here
   --> $DIR/rustc_deprecation-in-future.rs:3:9
@@ -10,5 +10,11 @@ note: the lint level is defined here
 LL | #![deny(deprecated_in_future)]
    |         ^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error: use of unit struct `S2` that will be deprecated in a future Rust version: literally never
+  --> $DIR/rustc_deprecation-in-future.rs:19:13
+   |
+LL |     let _ = S2;
+   |             ^^
+
+error: aborting due to 2 previous errors
 

src/test/ui/stability-attribute/stability-attribute-sanity.rs

@@ -63,7 +63,11 @@ fn multiple3() { }
 #[rustc_const_unstable(feature = "c", issue = "none")]
 #[rustc_const_unstable(feature = "d", issue = "none")] //~ ERROR multiple stability levels
 pub const fn multiple4() { }
-//~^ ERROR Invalid stability or deprecation version found
+//~^ ERROR Invalid stability version found
+
+#[stable(feature = "a", since = "1.0.0")]
+#[rustc_deprecated(since = "invalid", reason = "text")]
+fn invalid_deprecation_version() {} //~ ERROR Invalid deprecation version found
 
 #[rustc_deprecated(since = "a", reason = "text")]
 fn deprecated_without_unstable_or_stable() { }

src/test/ui/stability-attribute/stability-attribute-sanity.stderr

@@ -96,19 +96,25 @@ error[E0544]: multiple stability levels
 LL | #[rustc_const_unstable(feature = "d", issue = "none")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: Invalid stability or deprecation version found
+error: Invalid stability version found
   --> $DIR/stability-attribute-sanity.rs:65:1
    |
 LL | pub const fn multiple4() { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+error: Invalid deprecation version found
+  --> $DIR/stability-attribute-sanity.rs:70:1
+   |
+LL | fn invalid_deprecation_version() {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0549]: rustc_deprecated attribute must be paired with either stable or unstable attribute
-  --> $DIR/stability-attribute-sanity.rs:68:1
+  --> $DIR/stability-attribute-sanity.rs:72:1
    |
 LL | #[rustc_deprecated(since = "a", reason = "text")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 18 previous errors
+error: aborting due to 19 previous errors
 
 Some errors have detailed explanations: E0539, E0541, E0546, E0550.
 For more information about an error, try `rustc --explain E0539`.