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

12 files changed, 160 insertions, 30 deletions

diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 4c0eeba7441..da3d0d5ed3f 100644
--- a/src/librustc/session/config.rs
+++ b/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 |
diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs
index 82cc1b7f661..dd6f5fc0446 100644
--- a/src/librustc_mir/const_eval.rs
+++ b/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 {
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index e393aa99218..a19bf6d89cb 100644
--- a/src/librustc_resolve/lib.rs
+++ b/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 =
diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index b320ef032f2..6aac4c7945c 100644
--- a/src/librustc_resolve/macros.rs
+++ b/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
             });
diff --git a/src/librustc_resolve/resolve_imports.rs b/src/librustc_resolve/resolve_imports.rs
index e689e6d70fd..4cf1a0d8935 100644
--- a/src/librustc_resolve/resolve_imports.rs
+++ b/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() {
diff --git a/src/test/ui/consts/const-eval/union-ice.rs b/src/test/ui/consts/const-eval/union-ice.rs
index 0cdb78c9780..5d50004e554 100644
--- a/src/test/ui/consts/const-eval/union-ice.rs
+++ b/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 },
 };
diff --git a/src/test/ui/consts/const-eval/union-ice.stderr b/src/test/ui/consts/const-eval/union-ice.stderr
index e8a7b2f5005..ec51802681e 100644
--- a/src/test/ui/consts/const-eval/union-ice.stderr
+++ b/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
diff --git a/src/test/ui/imports/macros.rs b/src/test/ui/imports/macros.rs
index 47ab8fc6c2f..f7dc7ac9eac 100644
--- a/src/test/ui/imports/macros.rs
+++ b/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() {}
diff --git a/src/test/ui/imports/macros.stderr b/src/test/ui/imports/macros.stderr
index c54101fc6e6..209d449dfd8 100644
--- a/src/test/ui/imports/macros.stderr
+++ b/src/test/ui/imports/macros.stderr
@@ -1,21 +1,4 @@
 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
    |
 LL |     m! { //~ ERROR ambiguous
@@ -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`.
diff --git a/src/test/ui/issues/issue-54387.rs b/src/test/ui/issues/issue-54387.rs
new file mode 100644
index 00000000000..ac1033add0e
--- /dev/null
+++ b/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;
+}
diff --git a/src/test/ui/macros/ambiguity-legacy-vs-modern.rs b/src/test/ui/macros/ambiguity-legacy-vs-modern.rs
new file mode 100644
index 00000000000..216b9dd0526
--- /dev/null
+++ b/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() {}
diff --git a/src/test/ui/macros/ambiguity-legacy-vs-modern.stderr b/src/test/ui/macros/ambiguity-legacy-vs-modern.stderr
new file mode 100644
index 00000000000..b5e1e751737
--- /dev/null
+++ b/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`.