Auto merge of #54821 - pietroalbini:beta-backports, r=pietroalbini

[beta] Rollup backports

Merged and approved:

* #54605: resolve: Disambiguate a subset of conflicts "macro_rules" vs "macro name in module"
* #54557: incr.comp.: Don't automatically enable -Zshare-generics for incr. comp. builds.
* #54759: do not normalize non-scalar constants to a ConstValue::ScalarPair

Closes #54759
r? @ghost

Author: bors

src/librustc/session/config.rs

@@ -646,7 +646,6 @@ impl Options {
         match self.debugging_opts.share_generics {
             Some(setting) => setting,
             None => {
-                self.incremental.is_some() ||
                 match self.optimize {
                     OptLevel::No   |
                     OptLevel::Less |

src/librustc_mir/const_eval.rs

@@ -17,7 +17,7 @@ use rustc::hir::{self, def_id::DefId};
 use rustc::mir::interpret::ConstEvalErr;
 use rustc::mir;
 use rustc::ty::{self, TyCtxt, Instance, query::TyCtxtAt};
-use rustc::ty::layout::{LayoutOf, TyLayout};
+use rustc::ty::layout::{self, LayoutOf, TyLayout};
 use rustc::ty::subst::Subst;
 use rustc_data_structures::indexed_vec::IndexVec;
 
@@ -90,8 +90,18 @@ pub fn eval_promoted<'a, 'mir, 'tcx>(
 pub fn op_to_const<'tcx>(
     ecx: &EvalContext<'_, '_, 'tcx, CompileTimeEvaluator>,
     op: OpTy<'tcx>,
-    normalize: bool,
+    may_normalize: bool,
 ) -> EvalResult<'tcx, &'tcx ty::Const<'tcx>> {
+    // We do not normalize just any data.  Only scalar layout and fat pointers.
+    let normalize = may_normalize
+        && match op.layout.abi {
+            layout::Abi::Scalar(..) => true,
+            layout::Abi::ScalarPair(..) => {
+                // Must be a fat pointer
+                op.layout.ty.builtin_deref(true).is_some()
+            },
+            _ => false,
+        };
     let normalized_op = if normalize {
         ecx.try_read_value(op)?
     } else {

src/librustc_resolve/lib.rs

@@ -71,11 +71,10 @@ use syntax_pos::{Span, DUMMY_SP, MultiSpan};
 use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
 
 use std::cell::{Cell, RefCell};
-use std::cmp;
+use std::{cmp, fmt, iter, ptr};
 use std::collections::BTreeSet;
-use std::fmt;
-use std::iter;
 use std::mem::replace;
+use rustc_data_structures::ptr_key::PtrKey;
 use rustc_data_structures::sync::Lrc;
 
 use resolve_imports::{ImportDirective, ImportDirectiveSubclass, NameResolution, ImportResolver};
@@ -1113,6 +1112,17 @@ impl<'a> ModuleData<'a> {
     fn nearest_item_scope(&'a self) -> Module<'a> {
         if self.is_trait() { self.parent.unwrap() } else { self }
     }
+
+    fn is_ancestor_of(&self, mut other: &Self) -> bool {
+        while !ptr::eq(self, other) {
+            if let Some(parent) = other.parent {
+                other = parent;
+            } else {
+                return false;
+            }
+        }
+        true
+    }
 }
 
 impl<'a> fmt::Debug for ModuleData<'a> {
@@ -1407,6 +1417,7 @@ pub struct Resolver<'a, 'b: 'a> {
     block_map: NodeMap<Module<'a>>,
     module_map: FxHashMap<DefId, Module<'a>>,
     extern_module_map: FxHashMap<(DefId, bool /* MacrosOnly? */), Module<'a>>,
+    binding_parent_modules: FxHashMap<PtrKey<'a, NameBinding<'a>>, Module<'a>>,
 
     pub make_glob_map: bool,
     /// Maps imports to the names of items actually imported (this actually maps
@@ -1709,6 +1720,7 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
             module_map,
             block_map: NodeMap(),
             extern_module_map: FxHashMap(),
+            binding_parent_modules: FxHashMap(),
 
             make_glob_map: make_glob_map == MakeGlobMap::Yes,
             glob_map: NodeMap(),
@@ -4526,6 +4538,31 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
         vis.is_accessible_from(module.normal_ancestor_id, self)
     }
 
+    fn set_binding_parent_module(&mut self, binding: &'a NameBinding<'a>, module: Module<'a>) {
+        if let Some(old_module) = self.binding_parent_modules.insert(PtrKey(binding), module) {
+            if !ptr::eq(module, old_module) {
+                span_bug!(binding.span, "parent module is reset for binding");
+            }
+        }
+    }
+
+    fn disambiguate_legacy_vs_modern(
+        &self,
+        legacy: &'a NameBinding<'a>,
+        modern: &'a NameBinding<'a>,
+    ) -> bool {
+        // Some non-controversial subset of ambiguities "modern macro name" vs "macro_rules"
+        // is disambiguated to mitigate regressions from macro modularization.
+        // Scoping for `macro_rules` behaves like scoping for `let` at module level, in general.
+        match (self.binding_parent_modules.get(&PtrKey(legacy)),
+               self.binding_parent_modules.get(&PtrKey(modern))) {
+            (Some(legacy), Some(modern)) =>
+                legacy.normal_ancestor_id == modern.normal_ancestor_id &&
+                modern.is_ancestor_of(legacy),
+            _ => false,
+        }
+    }
+
     fn report_ambiguity_error(&self, ident: Ident, b1: &NameBinding, b2: &NameBinding) {
         let participle = |is_import: bool| if is_import { "imported" } else { "defined" };
         let msg1 =

src/librustc_resolve/macros.rs

@@ -956,11 +956,13 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                 },
                 (Some(legacy_binding), Ok((binding, FromPrelude(from_prelude))))
                         if legacy_binding.def() != binding.def_ignoring_ambiguity() &&
-                           (!from_prelude ||
+                           (!from_prelude &&
+                            !self.disambiguate_legacy_vs_modern(legacy_binding, binding) ||
                             legacy_binding.may_appear_after(parent_scope.expansion, binding)) => {
                     self.report_ambiguity_error(ident, legacy_binding, binding);
                 },
                 // OK, non-macro-expanded legacy wins over prelude even if defs are different
+                // Also, non-macro-expanded legacy wins over modern from the same module
                 // Also, legacy and modern can co-exist if their defs are same
                 (Some(legacy_binding), Ok(_)) |
                 // OK, unambiguous resolution
@@ -1096,6 +1098,7 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
             let def = Def::Macro(def_id, MacroKind::Bang);
             let vis = ty::Visibility::Invisible; // Doesn't matter for legacy bindings
             let binding = (def, vis, item.span, expansion).to_name_binding(self.arenas);
+            self.set_binding_parent_module(binding, self.current_module);
             let legacy_binding = self.arenas.alloc_legacy_binding(LegacyBinding {
                 parent_legacy_scope: *current_legacy_scope, binding, ident
             });

src/librustc_resolve/resolve_imports.rs

@@ -478,6 +478,7 @@ impl<'a, 'crateloader> Resolver<'a, 'crateloader> {
                       binding: &'a NameBinding<'a>)
                       -> Result<(), &'a NameBinding<'a>> {
         self.check_reserved_macro_name(ident, ns);
+        self.set_binding_parent_module(binding, module);
         self.update_resolution(module, ident, ns, |this, resolution| {
             if let Some(old_binding) = resolution.binding {
                 if binding.is_glob_import() {

src/test/ui/consts/const-eval/union-ice.rs

@@ -22,7 +22,7 @@ const UNION: DummyUnion = DummyUnion { field1: 1065353216 };
 
 const FIELD3: Field3 = unsafe { UNION.field3 }; //~ ERROR this constant cannot be used
 
-const FIELD_PATH: Struct = Struct { //~ ERROR this constant cannot be used
+const FIELD_PATH: Struct = Struct { //~ ERROR this constant likely exhibits undefined behavior
     a: 42,
     b: unsafe { UNION.field3 },
 };

src/test/ui/consts/const-eval/union-ice.stderr

@@ -6,14 +6,16 @@ LL | const FIELD3: Field3 = unsafe { UNION.field3 }; //~ ERROR this constant can
    |
    = note: #[deny(const_err)] on by default
 
-error: this constant cannot be used
+error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/union-ice.rs:25:1
    |
-LL | / const FIELD_PATH: Struct = Struct { //~ ERROR this constant cannot be used
+LL | / const FIELD_PATH: Struct = Struct { //~ ERROR this constant likely exhibits undefined behavior
 LL | |     a: 42,
 LL | |     b: unsafe { UNION.field3 },
 LL | | };
-   | |__^ attempted to read undefined bytes
+   | |__^ type validation failed: encountered undefined bytes at .b
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
 error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/union-ice.rs:35:1

src/test/ui/imports/macros.rs

@@ -45,7 +45,7 @@ mod m3 {
 mod m4 {
     macro_rules! m { () => {} }
     use two_macros::m;
-    m!(); //~ ERROR ambiguous
+    m!();
 }
 
 fn main() {}

src/test/ui/imports/macros.stderr

@@ -1,20 +1,3 @@
-error[E0659]: `m` is ambiguous
-  --> $DIR/macros.rs:48:5
-   |
-LL |     m!(); //~ ERROR ambiguous
-   |     ^ ambiguous name
-   |
-note: `m` could refer to the name defined here
-  --> $DIR/macros.rs:46:5
-   |
-LL |     macro_rules! m { () => {} }
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-note: `m` could also refer to the name imported here
-  --> $DIR/macros.rs:47:9
-   |
-LL |     use two_macros::m;
-   |         ^^^^^^^^^^^^^
-
 error[E0659]: `m` is ambiguous
   --> $DIR/macros.rs:26:5
    |
@@ -51,6 +34,6 @@ LL |     use two_macros::m;
    |         ^^^^^^^^^^^^^
    = note: macro-expanded macro imports do not shadow
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0659`.

src/test/ui/issues/issue-54387.rs

@@ -0,0 +1,12 @@
+// compile-pass
+
+pub struct GstRc {
+    _obj: *const (),
+    _borrowed: bool,
+}
+
+const FOO: Option<GstRc> = None;
+
+fn main() {
+    let _meh = FOO;
+}

src/test/ui/macros/ambiguity-legacy-vs-modern.rs

@@ -0,0 +1,46 @@
+// Some non-controversial subset of ambiguities "modern macro name" vs "macro_rules"
+// is disambiguated to mitigate regressions from macro modularization.
+// Scoping for `macro_rules` behaves like scoping for `let` at module level, in general.
+
+#![feature(decl_macro)]
+
+fn same_unnamed_mod() {
+    macro m() { 0 }
+
+    macro_rules! m { () => (()) }
+
+    m!() // OK
+}
+
+fn nested_unnamed_mod() {
+    macro m() { 0 }
+
+    {
+        macro_rules! m { () => (()) }
+
+        m!() // OK
+    }
+}
+
+fn nested_unnamed_mod_fail() {
+    macro_rules! m { () => (()) }
+
+    {
+        macro m() { 0 }
+
+        m!() //~ ERROR `m` is ambiguous
+    }
+}
+
+fn nexted_named_mod_fail() {
+    macro m() { 0 }
+
+    #[macro_use]
+    mod inner {
+        macro_rules! m { () => (()) }
+    }
+
+    m!() //~ ERROR `m` is ambiguous
+}
+
+fn main() {}

src/test/ui/macros/ambiguity-legacy-vs-modern.stderr

@@ -0,0 +1,37 @@
+error[E0659]: `m` is ambiguous
+  --> $DIR/ambiguity-legacy-vs-modern.rs:31:9
+   |
+LL |         m!() //~ ERROR `m` is ambiguous
+   |         ^ ambiguous name
+   |
+note: `m` could refer to the name defined here
+  --> $DIR/ambiguity-legacy-vs-modern.rs:26:5
+   |
+LL |     macro_rules! m { () => (()) }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: `m` could also refer to the name defined here
+  --> $DIR/ambiguity-legacy-vs-modern.rs:29:9
+   |
+LL |         macro m() { 0 }
+   |         ^^^^^^^^^^^^^^^
+
+error[E0659]: `m` is ambiguous
+  --> $DIR/ambiguity-legacy-vs-modern.rs:43:5
+   |
+LL |     m!() //~ ERROR `m` is ambiguous
+   |     ^ ambiguous name
+   |
+note: `m` could refer to the name defined here
+  --> $DIR/ambiguity-legacy-vs-modern.rs:40:9
+   |
+LL |         macro_rules! m { () => (()) }
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: `m` could also refer to the name defined here
+  --> $DIR/ambiguity-legacy-vs-modern.rs:36:5
+   |
+LL |     macro m() { 0 }
+   |     ^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0659`.