Rollup merge of #96913 - Urgau:rfc3239-part2, r=petrochenkov

RFC3239: Implement `cfg(target)` - Part 2

This pull-request implements the compact `cfg(target(..))` part of [RFC 3239](https://github.com/rust-lang/rust/issues/96901).

I recommend reviewing this PR on a per commit basics, because of some moving parts.

cc `@GuillaumeGomez`
r? `@petrochenkov`

compiler/rustc_attr/src/builtin.rs

@@ -454,6 +454,15 @@ pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 }
 
+#[derive(Clone, Debug)]
+pub struct Condition {
+    pub name: Symbol,
+    pub name_span: Span,
+    pub value: Option<Symbol>,
+    pub value_span: Option<Span>,
+    pub span: Span,
+}
+
 /// Tests if a cfg-pattern matches the cfg set
 pub fn cfg_matches(
     cfg: &ast::MetaItem,
@@ -462,70 +471,42 @@ pub fn cfg_matches(
     features: Option<&Features>,
 ) -> bool {
     eval_condition(cfg, sess, features, &mut |cfg| {
-        try_gate_cfg(cfg, sess, features);
-        let error = |span, msg| {
-            sess.span_diagnostic.span_err(span, msg);
-            true
-        };
-        if cfg.path.segments.len() != 1 {
-            return error(cfg.path.span, "`cfg` predicate key must be an identifier");
-        }
-        match &cfg.kind {
-            MetaItemKind::List(..) => {
-                error(cfg.span, "unexpected parentheses after `cfg` predicate key")
-            }
-            MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
-                handle_errors(
-                    sess,
-                    lit.span,
-                    AttrError::UnsupportedLiteral(
-                        "literal in `cfg` predicate value must be a string",
-                        lit.kind.is_bytestr(),
-                    ),
+        try_gate_cfg(cfg.name, cfg.span, sess, features);
+        if let Some(names_valid) = &sess.check_config.names_valid {
+            if !names_valid.contains(&cfg.name) {
+                sess.buffer_lint_with_diagnostic(
+                    UNEXPECTED_CFGS,
+                    cfg.span,
+                    lint_node_id,
+                    "unexpected `cfg` condition name",
+                    BuiltinLintDiagnostics::UnexpectedCfg((cfg.name, cfg.name_span), None),
                 );
-                true
-            }
-            MetaItemKind::NameValue(..) | MetaItemKind::Word => {
-                let ident = cfg.ident().expect("multi-segment cfg predicate");
-                let name = ident.name;
-                let value = cfg.value_str();
-                if let Some(names_valid) = &sess.check_config.names_valid {
-                    if !names_valid.contains(&name) {
-                        sess.buffer_lint_with_diagnostic(
-                            UNEXPECTED_CFGS,
-                            cfg.span,
-                            lint_node_id,
-                            "unexpected `cfg` condition name",
-                            BuiltinLintDiagnostics::UnexpectedCfg((name, ident.span), None),
-                        );
-                    }
-                }
-                if let Some(value) = value {
-                    if let Some(values) = &sess.check_config.values_valid.get(&name) {
-                        if !values.contains(&value) {
-                            sess.buffer_lint_with_diagnostic(
-                                UNEXPECTED_CFGS,
-                                cfg.span,
-                                lint_node_id,
-                                "unexpected `cfg` condition value",
-                                BuiltinLintDiagnostics::UnexpectedCfg(
-                                    (name, ident.span),
-                                    Some((value, cfg.name_value_literal_span().unwrap())),
-                                ),
-                            );
-                        }
-                    }
-                }
-                sess.config.contains(&(name, value))
             }
         }
+        if let Some(value) = cfg.value {
+            if let Some(values) = &sess.check_config.values_valid.get(&cfg.name) {
+                if !values.contains(&value) {
+                    sess.buffer_lint_with_diagnostic(
+                        UNEXPECTED_CFGS,
+                        cfg.span,
+                        lint_node_id,
+                        "unexpected `cfg` condition value",
+                        BuiltinLintDiagnostics::UnexpectedCfg(
+                            (cfg.name, cfg.name_span),
+                            cfg.value_span.map(|vs| (value, vs)),
+                        ),
+                    );
+                }
+            }
+        }
+        sess.config.contains(&(cfg.name, cfg.value))
     })
 }
 
-fn try_gate_cfg(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) {
-    let gate = find_gated_cfg(|sym| cfg.has_name(sym));
+fn try_gate_cfg(name: Symbol, span: Span, sess: &ParseSess, features: Option<&Features>) {
+    let gate = find_gated_cfg(|sym| sym == name);
     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
-        gate_cfg(&gated_cfg, cfg.span, sess, feats);
+        gate_cfg(&gated_cfg, span, sess, feats);
     }
 }
 
@@ -563,11 +544,11 @@ pub fn eval_condition(
     cfg: &ast::MetaItem,
     sess: &ParseSess,
     features: Option<&Features>,
-    eval: &mut impl FnMut(&ast::MetaItem) -> bool,
+    eval: &mut impl FnMut(Condition) -> bool,
 ) -> bool {
     match cfg.kind {
         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
-            try_gate_cfg(cfg, sess, features);
+            try_gate_cfg(sym::version, cfg.span, sess, features);
             let (min_version, span) = match &mis[..] {
                 [NestedMetaItem::Literal(Lit { kind: LitKind::Str(sym, ..), span, .. })] => {
                     (sym, span)
@@ -649,6 +630,25 @@ pub fn eval_condition(
 
                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
                 }
+                sym::target => {
+                    if let Some(features) = features && !features.cfg_target_compact {
+                        feature_err(
+                            sess,
+                            sym::cfg_target_compact,
+                            cfg.span,
+                            &"compact `cfg(target(..))` is experimental and subject to change"
+                        ).emit();
+                    }
+
+                    mis.iter().fold(true, |res, mi| {
+                        let mut mi = mi.meta_item().unwrap().clone();
+                        if let [seg, ..] = &mut mi.path.segments[..] {
+                            seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
+                        }
+
+                        res & eval_condition(&mi, sess, features, eval)
+                    })
+                }
                 _ => {
                     struct_span_err!(
                         sess.span_diagnostic,
@@ -662,7 +662,32 @@ pub fn eval_condition(
                 }
             }
         }
-        ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => eval(cfg),
+        ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
+            sess.span_diagnostic
+                .span_err(cfg.path.span, "`cfg` predicate key must be an identifier");
+            true
+        }
+        MetaItemKind::NameValue(ref lit) if !lit.kind.is_str() => {
+            handle_errors(
+                sess,
+                lit.span,
+                AttrError::UnsupportedLiteral(
+                    "literal in `cfg` predicate value must be a string",
+                    lit.kind.is_bytestr(),
+                ),
+            );
+            true
+        }
+        ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
+            let ident = cfg.ident().expect("multi-segment cfg predicate");
+            eval(Condition {
+                name: ident.name,
+                name_span: ident.span,
+                value: cfg.value_str(),
+                value_span: cfg.name_value_literal_span(),
+                span: cfg.span,
+            })
+        }
     }
 }
 

compiler/rustc_attr/src/lib.rs

@@ -4,6 +4,7 @@
 //! The goal is to move the definition of `MetaItem` and things that don't need to be in `syntax`
 //! to this crate.
 
+#![feature(let_chains)]
 #![feature(let_else)]
 
 #[macro_use]

compiler/rustc_feature/src/active.rs

@@ -319,6 +319,8 @@ declare_features! (
     (active, cfg_sanitize, "1.41.0", Some(39699), None),
     /// Allows `cfg(target_abi = "...")`.
     (active, cfg_target_abi, "1.55.0", Some(80970), None),
+    /// Allows `cfg(target(abi = "..."))`.
+    (active, cfg_target_compact, "1.63.0", Some(96901), None),
     /// Allows `cfg(target_has_atomic_load_store = "...")`.
     (active, cfg_target_has_atomic, "1.60.0", Some(94039), None),
     /// Allows `cfg(target_has_atomic_equal_alignment = "...")`.

compiler/rustc_span/src/symbol.rs

@@ -427,6 +427,7 @@ symbols! {
         cfg_panic,
         cfg_sanitize,
         cfg_target_abi,
+        cfg_target_compact,
         cfg_target_feature,
         cfg_target_has_atomic,
         cfg_target_has_atomic_equal_alignment,
@@ -1375,6 +1376,7 @@ symbols! {
         sym,
         sync,
         t32,
+        target,
         target_abi,
         target_arch,
         target_endian,

compiler/rustc_trait_selection/src/traits/on_unimplemented.rs

@@ -89,8 +89,8 @@ impl<'tcx> OnUnimplementedDirective {
                         None,
                     )
                 })?;
-            attr::eval_condition(cond, &tcx.sess.parse_sess, Some(tcx.features()), &mut |item| {
-                if let Some(symbol) = item.value_str() && let Err(guar) = parse_value(symbol) {
+            attr::eval_condition(cond, &tcx.sess.parse_sess, Some(tcx.features()), &mut |cfg| {
+                if let Some(value) = cfg.value && let Err(guar) = parse_value(value) {
                     errored = Some(guar);
                 }
                 true
@@ -226,14 +226,12 @@ impl<'tcx> OnUnimplementedDirective {
                 condition,
                 &tcx.sess.parse_sess,
                 Some(tcx.features()),
-                &mut |c| {
-                    c.ident().map_or(false, |ident| {
-                        let value = c.value_str().map(|s| {
-                            OnUnimplementedFormatString(s).format(tcx, trait_ref, &options_map)
-                        });
+                &mut |cfg| {
+                    let value = cfg.value.map(|v| {
+                        OnUnimplementedFormatString(v).format(tcx, trait_ref, &options_map)
+                    });
 
-                        options.contains(&(ident.name, value))
-                    })
+                    options.contains(&(cfg.name, value))
                 },
             ) {
                 debug!("evaluate: skipping {:?} due to condition", command);

src/test/ui/cfg/cfg-target-compact-errors.rs

@@ -0,0 +1,17 @@
+// check-fail
+
+#![feature(cfg_target_compact)]
+
+#[cfg(target(o::o))]
+//~^ ERROR `cfg` predicate key must be an identifier
+fn one() {}
+
+#[cfg(target(os = 8))]
+//~^ ERROR literal in `cfg` predicate value must be a string
+fn two() {}
+
+#[cfg(target(os = "linux", pointer(width = "64")))]
+//~^ ERROR invalid predicate `target_pointer`
+fn three() {}
+
+fn main() {}

src/test/ui/cfg/cfg-target-compact-errors.stderr

@@ -0,0 +1,22 @@
+error: `cfg` predicate key must be an identifier
+  --> $DIR/cfg-target-compact-errors.rs:5:14
+   |
+LL | #[cfg(target(o::o))]
+   |              ^^^^
+
+error[E0565]: literal in `cfg` predicate value must be a string
+  --> $DIR/cfg-target-compact-errors.rs:9:19
+   |
+LL | #[cfg(target(os = 8))]
+   |                   ^
+
+error[E0537]: invalid predicate `target_pointer`
+  --> $DIR/cfg-target-compact-errors.rs:13:28
+   |
+LL | #[cfg(target(os = "linux", pointer(width = "64")))]
+   |                            ^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0537, E0565.
+For more information about an error, try `rustc --explain E0537`.

src/test/ui/cfg/cfg-target-compact.rs

@@ -0,0 +1,10 @@
+// run-pass
+#![feature(cfg_target_compact)]
+
+#[cfg(target(os = "linux", pointer_width = "64"))]
+pub fn main() {
+}
+
+#[cfg(not(target(os = "linux", pointer_width = "64")))]
+pub fn main() {
+}

src/test/ui/check-cfg/compact-names.rs

@@ -0,0 +1,15 @@
+// This test check that we correctly emit an warning for compact cfg
+//
+// check-pass
+// compile-flags:--check-cfg=names() -Z unstable-options
+
+#![feature(cfg_target_compact)]
+
+#[cfg(target(os = "linux", arch = "arm"))]
+pub fn expected() {}
+
+#[cfg(target(os = "linux", architecture = "arm"))]
+//~^ WARNING unexpected `cfg` condition name
+pub fn unexpected() {}
+
+fn main() {}

src/test/ui/check-cfg/compact-names.stderr

@@ -0,0 +1,10 @@
+warning: unexpected `cfg` condition name
+  --> $DIR/compact-names.rs:11:28
+   |
+LL | #[cfg(target(os = "linux", architecture = "arm"))]
+   |                            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: 1 warning emitted
+

src/test/ui/check-cfg/compact-values.rs

@@ -0,0 +1,15 @@
+// This test check that we correctly emit an warning for compact cfg
+//
+// check-pass
+// compile-flags:--check-cfg=values() -Z unstable-options
+
+#![feature(cfg_target_compact)]
+
+#[cfg(target(os = "linux", arch = "arm"))]
+pub fn expected() {}
+
+#[cfg(target(os = "linux", arch = "X"))]
+//~^ WARNING unexpected `cfg` condition value
+pub fn unexpected() {}
+
+fn main() {}

src/test/ui/check-cfg/compact-values.stderr

@@ -0,0 +1,11 @@
+warning: unexpected `cfg` condition value
+  --> $DIR/compact-values.rs:11:28
+   |
+LL | #[cfg(target(os = "linux", arch = "X"))]
+   |                            ^^^^^^^^^^
+   |
+   = note: `#[warn(unexpected_cfgs)]` on by default
+   = note: expected values for `target_arch` are: aarch64, arm, avr, bpf, hexagon, m68k, mips, mips64, msp430, nvptx64, powerpc, powerpc64, riscv32, riscv64, s390x, sparc, sparc64, wasm32, wasm64, x86, x86_64
+
+warning: 1 warning emitted
+

src/test/ui/feature-gates/feature-gate-cfg-target-compact.rs

@@ -0,0 +1,13 @@
+#[cfg(target(os = "x"))] //~ ERROR compact `cfg(target(..))` is experimental
+struct Foo(u64, u64);
+
+#[cfg_attr(target(os = "x"), x)] //~ ERROR compact `cfg(target(..))` is experimental
+struct Bar(u64, u64);
+
+#[cfg(not(any(all(target(os = "x")))))] //~ ERROR compact `cfg(target(..))` is experimental
+fn foo() {}
+
+fn main() {
+    cfg!(target(os = "x"));
+    //~^ ERROR compact `cfg(target(..))` is experimental and subject to change
+}

src/test/ui/feature-gates/feature-gate-cfg-target-compact.stderr

@@ -0,0 +1,39 @@
+error[E0658]: compact `cfg(target(..))` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-target-compact.rs:1:7
+   |
+LL | #[cfg(target(os = "x"))]
+   |       ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #96901 <https://github.com/rust-lang/rust/issues/96901> for more information
+   = help: add `#![feature(cfg_target_compact)]` to the crate attributes to enable
+
+error[E0658]: compact `cfg(target(..))` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-target-compact.rs:4:12
+   |
+LL | #[cfg_attr(target(os = "x"), x)]
+   |            ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #96901 <https://github.com/rust-lang/rust/issues/96901> for more information
+   = help: add `#![feature(cfg_target_compact)]` to the crate attributes to enable
+
+error[E0658]: compact `cfg(target(..))` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-target-compact.rs:7:19
+   |
+LL | #[cfg(not(any(all(target(os = "x")))))]
+   |                   ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #96901 <https://github.com/rust-lang/rust/issues/96901> for more information
+   = help: add `#![feature(cfg_target_compact)]` to the crate attributes to enable
+
+error[E0658]: compact `cfg(target(..))` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-target-compact.rs:11:10
+   |
+LL |     cfg!(target(os = "x"));
+   |          ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #96901 <https://github.com/rust-lang/rust/issues/96901> for more information
+   = help: add `#![feature(cfg_target_compact)]` to the crate attributes to enable
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0658`.