Auto merge of #85335 - GuillaumeGomez:rollup-0tvc14g, r=GuillaumeGomez

Rollup of 4 pull requests

Successful merges:

 - #84751 (str::is_char_boundary - slight optimization)
 - #85185 (Generate not more docs than necessary)
 - #85324 (Warn about unused `pub` fields in non-`pub` structs)
 - #85329 (fix version_str comment)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

10 files changed, 126 insertions, 36 deletions

diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index fd29053433e..7b1660b501b 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -922,7 +922,7 @@ impl<'a> MutVisitor for ReplaceBodyWithLoop<'a, '_> {
     }
 }
 
-/// Returns a version string such as "rustc 1.46.0 (04488afe3 2020-08-24)"
+/// Returns a version string such as "1.46.0 (04488afe3 2020-08-24)"
 pub fn version_str() -> Option<&'static str> {
     option_env!("CFG_VERSION")
 }
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index d32180525bf..bd142677cf9 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -44,6 +44,7 @@ struct MarkSymbolVisitor<'tcx> {
     repr_has_repr_c: bool,
     in_pat: bool,
     inherited_pub_visibility: bool,
+    pub_visibility: bool,
     ignore_variant_stack: Vec<DefId>,
     // maps from tuple struct constructors to tuple struct items
     struct_constructors: FxHashMap<hir::HirId, hir::HirId>,
@@ -188,27 +189,33 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
 
     fn visit_node(&mut self, node: Node<'tcx>) {
         let had_repr_c = self.repr_has_repr_c;
-        self.repr_has_repr_c = false;
         let had_inherited_pub_visibility = self.inherited_pub_visibility;
+        let had_pub_visibility = self.pub_visibility;
+        self.repr_has_repr_c = false;
         self.inherited_pub_visibility = false;
+        self.pub_visibility = false;
         match node {
-            Node::Item(item) => match item.kind {
-                hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) => {
-                    let def = self.tcx.adt_def(item.def_id);
-                    self.repr_has_repr_c = def.repr.c();
+            Node::Item(item) => {
+                self.pub_visibility = item.vis.node.is_pub();
 
-                    intravisit::walk_item(self, &item);
-                }
-                hir::ItemKind::Enum(..) => {
-                    self.inherited_pub_visibility = item.vis.node.is_pub();
+                match item.kind {
+                    hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) => {
+                        let def = self.tcx.adt_def(item.def_id);
+                        self.repr_has_repr_c = def.repr.c();
 
-                    intravisit::walk_item(self, &item);
-                }
-                hir::ItemKind::ForeignMod { .. } => {}
-                _ => {
-                    intravisit::walk_item(self, &item);
+                        intravisit::walk_item(self, &item);
+                    }
+                    hir::ItemKind::Enum(..) => {
+                        self.inherited_pub_visibility = self.pub_visibility;
+
+                        intravisit::walk_item(self, &item);
+                    }
+                    hir::ItemKind::ForeignMod { .. } => {}
+                    _ => {
+                        intravisit::walk_item(self, &item);
+                    }
                 }
-            },
+            }
             Node::TraitItem(trait_item) => {
                 intravisit::walk_trait_item(self, trait_item);
             }
@@ -220,8 +227,9 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
             }
             _ => {}
         }
-        self.repr_has_repr_c = had_repr_c;
+        self.pub_visibility = had_pub_visibility;
         self.inherited_pub_visibility = had_inherited_pub_visibility;
+        self.repr_has_repr_c = had_repr_c;
     }
 
     fn mark_as_used_if_union(&mut self, adt: &ty::AdtDef, fields: &[hir::ExprField<'_>]) {
@@ -259,10 +267,10 @@ impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
     ) {
         let has_repr_c = self.repr_has_repr_c;
         let inherited_pub_visibility = self.inherited_pub_visibility;
-        let live_fields = def
-            .fields()
-            .iter()
-            .filter(|f| has_repr_c || inherited_pub_visibility || f.vis.node.is_pub());
+        let pub_visibility = self.pub_visibility;
+        let live_fields = def.fields().iter().filter(|f| {
+            has_repr_c || (pub_visibility && (inherited_pub_visibility || f.vis.node.is_pub()))
+        });
         self.live_symbols.extend(live_fields.map(|f| f.hir_id));
 
         intravisit::walk_struct_def(self, def);
@@ -500,6 +508,7 @@ fn find_live<'tcx>(
         repr_has_repr_c: false,
         in_pat: false,
         inherited_pub_visibility: false,
+        pub_visibility: false,
         ignore_variant_stack: vec![],
         struct_constructors,
     };
diff --git a/library/core/src/str/mod.rs b/library/core/src/str/mod.rs
index 95dd54976b2..065acd3f38b 100644
--- a/library/core/src/str/mod.rs
+++ b/library/core/src/str/mod.rs
@@ -192,14 +192,26 @@ impl str {
     #[stable(feature = "is_char_boundary", since = "1.9.0")]
     #[inline]
     pub fn is_char_boundary(&self, index: usize) -> bool {
-        // 0 and len are always ok.
+        // 0 is always ok.
         // Test for 0 explicitly so that it can optimize out the check
         // easily and skip reading string data for that case.
-        if index == 0 || index == self.len() {
+        // Note that optimizing `self.get(..index)` relies on this.
+        if index == 0 {
             return true;
         }
+
         match self.as_bytes().get(index) {
-            None => false,
+            // For `None` we have two options:
+            //
+            // - index == self.len()
+            //   Empty strings are valid, so return true
+            // - index > self.len()
+            //   In this case return false
+            //
+            // The check is placed exactly here, because it improves generated
+            // code on higher opt-levels. See PR #84751 for more details.
+            None => index == self.len(),
+
             // This is bit magic equivalent to: b < 128 || b >= 192
             Some(&b) => (b as i8) >= -0x40,
         }
diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index 326a6fdaa80..f9972ac7b9d 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -451,6 +451,22 @@ impl Step for Std {
 
             builder.run(&mut cargo.into());
         };
+
+        let paths = builder
+            .paths
+            .iter()
+            .map(components_simplified)
+            .filter_map(|path| {
+                if path.get(0) == Some(&"library") {
+                    Some(path[1].to_owned())
+                } else if !path.is_empty() {
+                    Some(path[0].to_owned())
+                } else {
+                    None
+                }
+            })
+            .collect::<Vec<_>>();
+
         // Only build the following crates. While we could just iterate over the
         // folder structure, that would also build internal crates that we do
         // not want to show in documentation. These crates will later be visited
@@ -464,20 +480,17 @@ impl Step for Std {
         let krates = ["core", "alloc", "std", "proc_macro", "test"];
         for krate in &krates {
             run_cargo_rustdoc_for(krate);
+            if paths.iter().any(|p| p == krate) {
+                // No need to document more of the libraries if we have the one we want.
+                break;
+            }
         }
         builder.cp_r(&out_dir, &out);
 
         // Look for library/std, library/core etc in the `x.py doc` arguments and
         // open the corresponding rendered docs.
-        for path in builder.paths.iter().map(components_simplified) {
-            let requested_crate = if path.get(0) == Some(&"library") {
-                &path[1]
-            } else if !path.is_empty() {
-                &path[0]
-            } else {
-                continue;
-            };
-            if krates.contains(&requested_crate) {
+        for requested_crate in paths {
+            if krates.iter().any(|k| *k == requested_crate.as_str()) {
                 let index = out.join(requested_crate).join("index.html");
                 open(builder, &index);
             }
diff --git a/src/ci/docker/host-x86_64/mingw-check/Dockerfile b/src/ci/docker/host-x86_64/mingw-check/Dockerfile
index a9398649cf0..fd6dc563a0e 100644
--- a/src/ci/docker/host-x86_64/mingw-check/Dockerfile
+++ b/src/ci/docker/host-x86_64/mingw-check/Dockerfile
@@ -34,7 +34,7 @@ ENV SCRIPT python3 ../x.py --stage 2 test src/tools/expand-yaml-anchors && \
            python3 ../x.py build --stage 0 src/tools/build-manifest && \
            python3 ../x.py test --stage 0 src/tools/compiletest && \
            python3 ../x.py test --stage 2 src/tools/tidy && \
-           python3 ../x.py doc --stage 0 library/std && \
+           python3 ../x.py doc --stage 0 library/test && \
            /scripts/validate-toolstate.sh && \
            # Runs checks to ensure that there are no ES5 issues in our JS code.
            es-check es5 ../src/librustdoc/html/static/*.js
diff --git a/src/test/ui/cast/issue-84213.fixed b/src/test/ui/cast/issue-84213.fixed
index e1a60557a20..b5c4a775296 100644
--- a/src/test/ui/cast/issue-84213.fixed
+++ b/src/test/ui/cast/issue-84213.fixed
@@ -6,6 +6,7 @@ struct Something {
 
 fn main() {
     let mut something = Something { field: 1337 };
+    let _ = something.field;
 
     let _pointer_to_something = &something as *const Something;
     //~^ ERROR: non-primitive cast
diff --git a/src/test/ui/cast/issue-84213.rs b/src/test/ui/cast/issue-84213.rs
index 3df264bdffb..6eb81291abc 100644
--- a/src/test/ui/cast/issue-84213.rs
+++ b/src/test/ui/cast/issue-84213.rs
@@ -6,6 +6,7 @@ struct Something {
 
 fn main() {
     let mut something = Something { field: 1337 };
+    let _ = something.field;
 
     let _pointer_to_something = something as *const Something;
     //~^ ERROR: non-primitive cast
diff --git a/src/test/ui/cast/issue-84213.stderr b/src/test/ui/cast/issue-84213.stderr
index a76aac58013..1b71d4db511 100644
--- a/src/test/ui/cast/issue-84213.stderr
+++ b/src/test/ui/cast/issue-84213.stderr
@@ -1,5 +1,5 @@
 error[E0605]: non-primitive cast: `Something` as `*const Something`
-  --> $DIR/issue-84213.rs:10:33
+  --> $DIR/issue-84213.rs:11:33
    |
 LL |     let _pointer_to_something = something as *const Something;
    |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ invalid cast
@@ -10,7 +10,7 @@ LL |     let _pointer_to_something = &something as *const Something;
    |                                 ^
 
 error[E0605]: non-primitive cast: `Something` as `*mut Something`
-  --> $DIR/issue-84213.rs:13:37
+  --> $DIR/issue-84213.rs:14:37
    |
 LL |     let _mut_pointer_to_something = something as *mut Something;
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ invalid cast
diff --git a/src/test/ui/lint/dead-code/issue-85255.rs b/src/test/ui/lint/dead-code/issue-85255.rs
new file mode 100644
index 00000000000..9a4d9fbad35
--- /dev/null
+++ b/src/test/ui/lint/dead-code/issue-85255.rs
@@ -0,0 +1,22 @@
+// Unused `pub` fields in non-`pub` structs should also trigger dead code warnings.
+// check-pass
+
+#![warn(dead_code)]
+
+struct Foo {
+    a: i32, //~ WARNING: field is never read
+    pub b: i32, //~ WARNING: field is never read
+}
+
+struct Bar;
+
+impl Bar {
+    fn a(&self) -> i32 { 5 } //~ WARNING: associated function is never used
+    pub fn b(&self) -> i32 { 6 } //~ WARNING: associated function is never used
+}
+
+
+fn main() {
+    let _ = Foo { a: 1, b: 2 };
+    let _ = Bar;
+}
diff --git a/src/test/ui/lint/dead-code/issue-85255.stderr b/src/test/ui/lint/dead-code/issue-85255.stderr
new file mode 100644
index 00000000000..73646439295
--- /dev/null
+++ b/src/test/ui/lint/dead-code/issue-85255.stderr
@@ -0,0 +1,32 @@
+warning: field is never read: `a`
+  --> $DIR/issue-85255.rs:7:5
+   |
+LL |     a: i32,
+   |     ^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/issue-85255.rs:4:9
+   |
+LL | #![warn(dead_code)]
+   |         ^^^^^^^^^
+
+warning: field is never read: `b`
+  --> $DIR/issue-85255.rs:8:5
+   |
+LL |     pub b: i32,
+   |     ^^^^^^^^^^
+
+warning: associated function is never used: `a`
+  --> $DIR/issue-85255.rs:14:8
+   |
+LL |     fn a(&self) -> i32 { 5 }
+   |        ^
+
+warning: associated function is never used: `b`
+  --> $DIR/issue-85255.rs:15:12
+   |
+LL |     pub fn b(&self) -> i32 { 6 }
+   |            ^
+
+warning: 4 warnings emitted
+