be even more precise about "cast" vs "coercion"

5 files changed, 19 insertions, 6 deletions

diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 47fea6f6d90..70331214ac5 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -234,8 +234,8 @@ pub enum ConstraintCategory<'tcx> {
     UseAsStatic,
     TypeAnnotation,
     Cast {
-        /// Whether this cast is a coercion.
-        is_coercion: bool,
+        /// Whether this cast is a coercion that was automatically inserted by the compiler.
+        is_implicit_coercion: bool,
         /// Whether this is an unsizing coercion and if yes, this contains the target type.
         /// Region variables are erased to ReErased.
         #[derive_where(skip)]
diff --git a/compiler/rustc_middle/src/mir/statement.rs b/compiler/rustc_middle/src/mir/statement.rs
index c3891e70e93..88ed90c3114 100644
--- a/compiler/rustc_middle/src/mir/statement.rs
+++ b/compiler/rustc_middle/src/mir/statement.rs
@@ -432,7 +432,7 @@ impl<'tcx> Rvalue<'tcx> {
                 | CastKind::IntToFloat
                 | CastKind::FnPtrToPtr
                 | CastKind::PtrToPtr
-                | CastKind::PointerCoercion(_)
+                | CastKind::PointerCoercion(_, _)
                 | CastKind::PointerWithExposedProvenance
                 | CastKind::Transmute,
                 _,
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index ff7360f06ed..bba3aee820a 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -579,7 +579,7 @@ pub struct CopyNonOverlapping<'tcx> {
     pub count: Operand<'tcx>,
 }
 
-/// Represents how a `TerminatorKind::Call` was constructed, used for diagnostics
+/// Represents how a [`TerminatorKind::Call`] was constructed, used for diagnostics.
 #[derive(Clone, Copy, TyEncodable, TyDecodable, Debug, PartialEq, Hash, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub enum CallSource {
@@ -1403,7 +1403,7 @@ pub enum CastKind {
     /// * [`PointerCoercion::MutToConstPointer`]
     ///
     /// Both are runtime nops, so should be [`CastKind::PtrToPtr`] instead in runtime MIR.
-    PointerCoercion(PointerCoercion),
+    PointerCoercion(PointerCoercion, CoercionSource),
     IntToInt,
     FloatToInt,
     FloatToFloat,
@@ -1419,6 +1419,15 @@ pub enum CastKind {
     Transmute,
 }
 
+/// Represents how a [`CastKind::PointerCoercion`] was constructed, used for diagnostics.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
+pub enum CoercionSource {
+    /// The coercion was manually written by the user with an `as` cast.
+    AsCast,
+    /// The coercion was automatically inserted by the compiler.
+    Implicit,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub enum AggregateKind<'tcx> {
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 5b4f10e52ad..e614d41899a 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -338,6 +338,8 @@ pub enum ExprKind<'tcx> {
     PointerCoercion {
         cast: PointerCoercion,
         source: ExprId,
+        /// Whether this coercion is written with an `as` cast in the source code.
+        is_from_as_cast: bool,
     },
     /// A `loop` expression.
     Loop {
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index af2e914cbf1..58e2ebaeaf8 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -68,7 +68,9 @@ pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
         Cast { source } => visitor.visit_expr(&visitor.thir()[source]),
         Use { source } => visitor.visit_expr(&visitor.thir()[source]),
         NeverToAny { source } => visitor.visit_expr(&visitor.thir()[source]),
-        PointerCoercion { source, cast: _ } => visitor.visit_expr(&visitor.thir()[source]),
+        PointerCoercion { source, cast: _, is_from_as_cast: _ } => {
+            visitor.visit_expr(&visitor.thir()[source])
+        }
         Let { expr, ref pat } => {
             visitor.visit_expr(&visitor.thir()[expr]);
             visitor.visit_pat(pat);