Auto merge of #91555 - matthiaskrgr:rollup-pq0iaq7, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - #90529 (Skip reborrows in AbstractConstBuilder)
 - #91437 (Pretty print empty blocks as {})
 - #91450 (Don't suggest types whose inner type is erroneous)
 - #91535 (Stabilize `-Z emit-future-incompat` as `--json future-incompat`)

Failed merges:

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

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -263,14 +263,17 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         self.strsep(",", false, b, elts, op)
     }
 
-    fn maybe_print_comment(&mut self, pos: BytePos) {
+    fn maybe_print_comment(&mut self, pos: BytePos) -> bool {
+        let mut has_comment = false;
         while let Some(ref cmnt) = self.next_comment() {
             if cmnt.pos < pos {
+                has_comment = true;
                 self.print_comment(cmnt);
             } else {
                 break;
             }
         }
+        has_comment
     }
 
     fn print_comment(&mut self, cmnt: &Comment) {
@@ -570,7 +573,10 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         self.print_tts(tts, convert_dollar_crate);
         self.end();
         match delim {
-            DelimToken::Brace => self.bclose(span),
+            DelimToken::Brace => {
+                let empty = tts.is_empty();
+                self.bclose(span, empty);
+            }
             _ => {
                 let token_str = self.token_kind_to_string(&token::CloseDelim(delim));
                 self.word(token_str)
@@ -642,17 +648,20 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         self.end(); // Close the head-box.
     }
 
-    fn bclose_maybe_open(&mut self, span: rustc_span::Span, close_box: bool) {
-        self.maybe_print_comment(span.hi());
+    fn bclose_maybe_open(&mut self, span: rustc_span::Span, empty: bool, close_box: bool) {
+        let has_comment = self.maybe_print_comment(span.hi());
+        if !empty || has_comment {
             self.break_offset_if_not_bol(1, -(INDENT_UNIT as isize));
+        }
         self.word("}");
         if close_box {
             self.end(); // Close the outer-box.
         }
     }
 
-    fn bclose(&mut self, span: rustc_span::Span) {
-        self.bclose_maybe_open(span, true)
+    fn bclose(&mut self, span: rustc_span::Span, empty: bool) {
+        let close_box = true;
+        self.bclose_maybe_open(span, empty, close_box)
     }
 
     fn break_offset_if_not_bol(&mut self, n: usize, off: isize) {
@@ -1196,7 +1205,8 @@ impl<'a> State<'a> {
                         for item in items {
                             self.print_item(item);
                         }
-                        self.bclose(item.span);
+                        let empty = item.attrs.is_empty() && items.is_empty();
+                        self.bclose(item.span, empty);
                     }
                     ModKind::Unloaded => {
                         self.s.word(";");
@@ -1216,7 +1226,8 @@ impl<'a> State<'a> {
                 }
                 self.bopen();
                 self.print_foreign_mod(nmod, &item.attrs);
-                self.bclose(item.span);
+                let empty = item.attrs.is_empty() && nmod.items.is_empty();
+                self.bclose(item.span, empty);
             }
             ast::ItemKind::GlobalAsm(ref asm) => {
                 self.head(visibility_qualified(&item.vis, "global_asm!"));
@@ -1291,7 +1302,8 @@ impl<'a> State<'a> {
                 for impl_item in items {
                     self.print_assoc_item(impl_item);
                 }
-                self.bclose(item.span);
+                let empty = item.attrs.is_empty() && items.is_empty();
+                self.bclose(item.span, empty);
             }
             ast::ItemKind::Trait(box ast::Trait {
                 is_auto,
@@ -1326,7 +1338,8 @@ impl<'a> State<'a> {
                 for trait_item in items {
                     self.print_assoc_item(trait_item);
                 }
-                self.bclose(item.span);
+                let empty = item.attrs.is_empty() && items.is_empty();
+                self.bclose(item.span, empty);
             }
             ast::ItemKind::TraitAlias(ref generics, ref bounds) => {
                 self.head("");
@@ -1410,7 +1423,8 @@ impl<'a> State<'a> {
             self.end();
             self.maybe_print_trailing_comment(v.span, None);
         }
-        self.bclose(span)
+        let empty = variants.is_empty();
+        self.bclose(span, empty)
     }
 
     crate fn print_visibility(&mut self, vis: &ast::Visibility) {
@@ -1441,6 +1455,9 @@ impl<'a> State<'a> {
     crate fn print_record_struct_body(&mut self, fields: &[ast::FieldDef], span: rustc_span::Span) {
         self.nbsp();
         self.bopen();
+
+        let empty = fields.is_empty();
+        if !empty {
             self.hardbreak_if_not_bol();
 
             for field in fields {
@@ -1453,8 +1470,9 @@ impl<'a> State<'a> {
                 self.print_type(&field.ty);
                 self.s.word(",");
             }
+        }
 
-        self.bclose(span)
+        self.bclose(span, empty);
     }
 
     crate fn print_struct(
@@ -1633,7 +1651,8 @@ impl<'a> State<'a> {
             }
         }
 
-        self.bclose_maybe_open(blk.span, close_box);
+        let empty = attrs.is_empty() && blk.stmts.is_empty();
+        self.bclose_maybe_open(blk.span, empty, close_box);
         self.ann.post(self, AnnNode::Block(blk))
     }
 
@@ -2010,7 +2029,8 @@ impl<'a> State<'a> {
                 for arm in arms {
                     self.print_arm(arm);
                 }
-                self.bclose(expr.span);
+                let empty = attrs.is_empty() && arms.is_empty();
+                self.bclose(expr.span, empty);
             }
             ast::ExprKind::Closure(
                 capture_clause,

compiler/rustc_hir_pretty/src/lib.rs

@@ -2174,7 +2174,7 @@ impl<'a> State<'a> {
         match decl.output {
             hir::FnRetTy::Return(ref ty) => {
                 self.print_type(&ty);
-                self.maybe_print_comment(ty.span.lo())
+                self.maybe_print_comment(ty.span.lo());
             }
             hir::FnRetTy::DefaultReturn(..) => unreachable!(),
         }
@@ -2368,7 +2368,7 @@ impl<'a> State<'a> {
         self.end();
 
         if let hir::FnRetTy::Return(ref output) = decl.output {
-            self.maybe_print_comment(output.span.lo())
+            self.maybe_print_comment(output.span.lo());
         }
     }
 

compiler/rustc_interface/src/tests.rs

@@ -651,7 +651,6 @@ fn test_debugging_options_tracking_hash() {
     untracked!(dump_mir_dir, String::from("abc"));
     untracked!(dump_mir_exclude_pass_number, true);
     untracked!(dump_mir_graphviz, true);
-    untracked!(emit_future_incompat_report, true);
     untracked!(emit_stack_sizes, true);
     untracked!(future_incompat_test, true);
     untracked!(hir_stats, true);

compiler/rustc_session/src/config.rs

@@ -746,6 +746,7 @@ impl Default for Options {
             edition: DEFAULT_EDITION,
             json_artifact_notifications: false,
             json_unused_externs: false,
+            json_future_incompat: false,
             pretty: None,
             working_dir: RealFileName::LocalPath(std::env::current_dir().unwrap()),
         }
@@ -1257,6 +1258,7 @@ pub struct JsonConfig {
     pub json_rendered: HumanReadableErrorType,
     pub json_artifact_notifications: bool,
     pub json_unused_externs: bool,
+    pub json_future_incompat: bool,
 }
 
 /// Parse the `--json` flag.
@@ -1269,6 +1271,7 @@ pub fn parse_json(matches: &getopts::Matches) -> JsonConfig {
     let mut json_color = ColorConfig::Never;
     let mut json_artifact_notifications = false;
     let mut json_unused_externs = false;
+    let mut json_future_incompat = false;
     for option in matches.opt_strs("json") {
         // For now conservatively forbid `--color` with `--json` since `--json`
         // won't actually be emitting any colors and anything colorized is
@@ -1286,6 +1289,7 @@ pub fn parse_json(matches: &getopts::Matches) -> JsonConfig {
                 "diagnostic-rendered-ansi" => json_color = ColorConfig::Always,
                 "artifacts" => json_artifact_notifications = true,
                 "unused-externs" => json_unused_externs = true,
+                "future-incompat" => json_future_incompat = true,
                 s => early_error(
                     ErrorOutputType::default(),
                     &format!("unknown `--json` option `{}`", s),
@@ -1298,6 +1302,7 @@ pub fn parse_json(matches: &getopts::Matches) -> JsonConfig {
         json_rendered: json_rendered(json_color),
         json_artifact_notifications,
         json_unused_externs,
+        json_future_incompat,
     }
 }
 
@@ -2011,8 +2016,12 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
 
     let edition = parse_crate_edition(matches);
 
-    let JsonConfig { json_rendered, json_artifact_notifications, json_unused_externs } =
-        parse_json(matches);
+    let JsonConfig {
+        json_rendered,
+        json_artifact_notifications,
+        json_unused_externs,
+        json_future_incompat,
+    } = parse_json(matches);
 
     let error_format = parse_error_format(matches, color, json_rendered);
 
@@ -2248,6 +2257,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         edition,
         json_artifact_notifications,
         json_unused_externs,
+        json_future_incompat,
         pretty,
         working_dir,
     }

compiler/rustc_session/src/options.rs

@@ -228,6 +228,9 @@ top_level_options!(
         /// `true` if we're emitting a JSON blob containing the unused externs
         json_unused_externs: bool [UNTRACKED],
 
+        /// `true` if we're emitting a JSON job containg a future-incompat report for lints
+        json_future_incompat: bool [TRACKED],
+
         pretty: Option<PpMode> [UNTRACKED],
 
         /// The (potentially remapped) working directory
@@ -1147,8 +1150,6 @@ options! {
         computed `block` spans (one span encompassing a block's terminator and \
         all statements). If `-Z instrument-coverage` is also enabled, create \
         an additional `.html` file showing the computed coverage spans."),
-    emit_future_incompat_report: bool = (false, parse_bool, [UNTRACKED],
-        "emits a future-incompatibility report for lints (RFC 2834)"),
     emit_stack_sizes: bool = (false, parse_bool, [UNTRACKED],
         "emit a section containing stack size metadata (default: no)"),
     fewer_names: Option<bool> = (None, parse_opt_bool, [TRACKED],

compiler/rustc_session/src/session.rs

@@ -280,7 +280,7 @@ impl Session {
     }
 
     fn emit_future_breakage(&self) {
-        if !self.opts.debugging_opts.emit_future_incompat_report {
+        if !self.opts.json_future_incompat {
             return;
         }
 

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

@@ -399,13 +399,25 @@ impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
                 let arg = self.recurse_build(source)?;
                 self.nodes.push(Node::Cast(abstract_const::CastKind::As, arg, node.ty))
             }
+            ExprKind::Borrow{ arg, ..} => {
+                let arg_node = &self.body.exprs[*arg];
 
-            // FIXME(generic_const_exprs): We may want to support these.
-            ExprKind::AddressOf { .. }
-            | ExprKind::Borrow { .. }
-            | ExprKind::Deref { .. } => self.maybe_supported_error(
+                // Skip reborrows for now until we allow Deref/Borrow/AddressOf
+                // expressions.
+                // FIXME(generic_const_exprs): Verify/explain why this is sound
+                if let ExprKind::Deref {arg} = arg_node.kind {
+                    self.recurse_build(arg)?
+                } else {
+                    self.maybe_supported_error(
                         node.span,
-                "dereferencing is not supported in generic constants",
+                        "borrowing is not supported in generic constants",
+                    )?
+                }
+            }
+            // FIXME(generic_const_exprs): We may want to support these.
+            ExprKind::AddressOf { .. } | ExprKind::Deref {..}=> self.maybe_supported_error(
+                node.span,
+                "dereferencing or taking the address is not supported in generic constants",
             )?,
             ExprKind::Repeat { .. } | ExprKind::Array { .. } =>  self.maybe_supported_error(
                 node.span,

compiler/rustc_typeck/src/collect.rs

@@ -41,7 +41,7 @@ use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::util::Discr;
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
-use rustc_middle::ty::{ReprOptions, ToPredicate, WithConstness};
+use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable, WithConstness};
 use rustc_session::lint;
 use rustc_session::parse::feature_err;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
@@ -1777,7 +1777,7 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
                     visitor.visit_ty(ty);
                     let mut diag = bad_placeholder_type(tcx, visitor.0, "return type");
                     let ret_ty = fn_sig.skip_binder().output();
-                    if ret_ty != tcx.ty_error() {
+                    if !ret_ty.references_error() {
                         if !ret_ty.is_closure() {
                             let ret_ty_str = match ret_ty.kind() {
                                 // Suggest a function pointer return type instead of a unique function definition

src/test/pretty/block-comment-trailing-whitespace2.rs

@@ -1,8 +1,7 @@
 // compile-flags: --crate-type=lib
 
 // pp-exact
-fn f() {
-} /*
+fn f() {} /*
           The next line should not be indented.
 
           That one. It shouldn't have been indented.

src/test/ui/const-generics/generic_const_exprs/closures.stderr

@@ -4,7 +4,7 @@ error: overly complex generic constant
 LL | fn test<const N: usize>() -> [u8; N + (|| 42)()] {}
    |                                   ^^^^-------^^
    |                                       |
-   |                                       dereferencing is not supported in generic constants
+   |                                       borrowing is not supported in generic constants
    |
    = help: consider moving this anonymous constant into a `const` function
    = note: this operation may be supported in the future

src/test/ui/const-generics/issues/issue-90455.rs

@@ -0,0 +1,12 @@
+#![feature(generic_const_exprs, adt_const_params)]
+#![allow(incomplete_features)]
+
+struct FieldElement<const N: &'static str> {
+    n: [u64; num_limbs(N)],
+    //~^ ERROR unconstrained generic constant
+}
+const fn num_limbs(_: &str) -> usize {
+    0
+}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-90455.stderr

@@ -0,0 +1,10 @@
+error: unconstrained generic constant
+  --> $DIR/issue-90455.rs:5:8
+   |
+LL |     n: [u64; num_limbs(N)],
+   |        ^^^^^^^^^^^^^^^^^^^
+   |
+   = help: try adding a `where` bound using this expression: `where [(); num_limbs(N)]:`
+
+error: aborting due to previous error
+

src/test/ui/lint/future-incompat-test.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Zfuture-incompat-test -Zemit-future-incompat-report
+// compile-flags: -Zfuture-incompat-test
 // check-pass
 
 // The `-Zfuture-incompat-test flag causes any normal warning to be included

src/test/ui/repr/issue-83921-pretty.pretty.stdout

@@ -13,7 +13,6 @@ extern crate std;
 // [pretty]compile-flags: -Zunpretty=everybody_loops
 // [pretty]check-pass
 #[repr("C")]
-struct A {
-}
+struct A {}
 
 fn main() { loop {} }

src/test/ui/typeck/issue-91450-inner-ty-error.rs

@@ -0,0 +1,7 @@
+// Regression test for #91450.
+// This test ensures that the compiler does not suggest `Foo<[type error]>` in diagnostic messages.
+
+fn foo() -> Option<_> {} //~ ERROR: [E0308]
+//~^ ERROR: the type placeholder `_` is not allowed
+
+fn main() {}

src/test/ui/typeck/issue-91450-inner-ty-error.stderr

@@ -0,0 +1,21 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-91450-inner-ty-error.rs:4:13
+   |
+LL | fn foo() -> Option<_> {}
+   |    ---      ^^^^^^^^^ expected enum `Option`, found `()`
+   |    |
+   |    implicitly returns `()` as its body has no tail or `return` expression
+   |
+   = note:   expected enum `Option<_>`
+           found unit type `()`
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures for return types
+  --> $DIR/issue-91450-inner-ty-error.rs:4:20
+   |
+LL | fn foo() -> Option<_> {}
+   |                    ^ not allowed in type signatures
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0121, E0308.
+For more information about an error, try `rustc --explain E0121`.

src/tools/compiletest/src/runtest.rs

@@ -1802,6 +1802,7 @@ impl<'test> TestCx<'test> {
                 // patterns still match the raw compiler output.
                 if self.props.error_patterns.is_empty() {
                     rustc.args(&["--error-format", "json"]);
+                    rustc.args(&["--json", "future-incompat"]);
                 }
                 rustc.arg("-Zui-testing");
                 rustc.arg("-Zdeduplicate-diagnostics=no");
@@ -1809,11 +1810,11 @@ impl<'test> TestCx<'test> {
             Ui => {
                 if !self.props.compile_flags.iter().any(|s| s.starts_with("--error-format")) {
                     rustc.args(&["--error-format", "json"]);
+                    rustc.args(&["--json", "future-incompat"]);
                 }
                 rustc.arg("-Ccodegen-units=1");
                 rustc.arg("-Zui-testing");
                 rustc.arg("-Zdeduplicate-diagnostics=no");
-                rustc.arg("-Zemit-future-incompat-report");
             }
             MirOpt => {
                 rustc.args(&[