Merge #4743

4743: Add tracking of packed repr, use it to highlight unsafe refs r=matklad a=Nashenas88

Taking a reference to a misaligned field on a packed struct is an
unsafe operation. Highlight that behavior. Currently, the misaligned
part isn't tracked, so this highlight is a bit too aggressive.

Fixes #4600

Co-authored-by: Paul Daniel Faria <[email protected]>
Co-authored-by: Paul Daniel Faria <[email protected]>
Co-authored-by: Paul Daniel Faria <[email protected]>

3 files changed, 117 insertions, 2 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 44456e49e..0007d7fa8 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -4,6 +4,7 @@ use std::{iter, sync::Arc};
 use arrayvec::ArrayVec;
 use either::Either;
 use hir_def::{
+    adt::ReprKind,
     adt::StructKind,
     adt::VariantData,
     builtin_type::BuiltinType,
@@ -431,6 +432,10 @@ impl Struct {
         Type::from_def(db, self.id.lookup(db.upcast()).container.module(db.upcast()).krate, self.id)
     }
 
+    pub fn repr(self, db: &dyn HirDatabase) -> Option<ReprKind> {
+        db.struct_data(self.id).repr.clone()
+    }
+
     fn variant_data(self, db: &dyn HirDatabase) -> Arc<VariantData> {
         db.struct_data(self.id).variant_data.clone()
     }
@@ -1253,6 +1258,19 @@ impl Type {
         )
     }
 
+    pub fn is_packed(&self, db: &dyn HirDatabase) -> bool {
+        let adt_id = match self.ty.value {
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::Adt(adt_id), .. }) => adt_id,
+            _ => return false,
+        };
+
+        let adt = adt_id.into();
+        match adt {
+            Adt::Struct(s) => matches!(s.repr(db), Some(ReprKind::Packed)),
+            _ => false,
+        }
+    }
+
     pub fn is_raw_ptr(&self) -> bool {
         matches!(&self.ty.value, Ty::Apply(ApplicationTy { ctor: TypeCtor::RawPtr(..), .. }))
     }
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 31f3241c9..34b02c536 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -49,7 +49,7 @@ pub use hir_def::{
     docs::Documentation,
     nameres::ModuleSource,
     path::{ModPath, Path, PathKind},
-    type_ref::Mutability,
+    type_ref::{Mutability, TypeRef},
 };
 pub use hir_expand::{
     hygiene::Hygiene, name::Name, HirFileId, InFile, MacroCallId, MacroCallLoc,
diff --git a/crates/ra_hir/src/semantics.rs b/crates/ra_hir/src/semantics.rs
index e392130ab..872f5fa4c 100644
--- a/crates/ra_hir/src/semantics.rs
+++ b/crates/ra_hir/src/semantics.rs
@@ -25,7 +25,8 @@ use crate::{
     semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
     source_analyzer::{resolve_hir_path, resolve_hir_path_qualifier, SourceAnalyzer},
     AssocItem, Callable, Crate, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef,
-    Module, ModuleDef, Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, VariantDef,
+    Module, ModuleDef, Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, TypeRef,
+    VariantDef,
 };
 use resolver::TypeNs;
 
@@ -279,6 +280,18 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
     pub fn assert_contains_node(&self, node: &SyntaxNode) {
         self.imp.assert_contains_node(node)
     }
+
+    pub fn is_unsafe_method_call(&self, method_call_expr: ast::MethodCallExpr) -> bool {
+        self.imp.is_unsafe_method_call(method_call_expr)
+    }
+
+    pub fn is_unsafe_ref_expr(&self, ref_expr: &ast::RefExpr) -> bool {
+        self.imp.is_unsafe_ref_expr(ref_expr)
+    }
+
+    pub fn is_unsafe_ident_pat(&self, ident_pat: &ast::IdentPat) -> bool {
+        self.imp.is_unsafe_ident_pat(ident_pat)
+    }
 }
 
 impl<'db> SemanticsImpl<'db> {
@@ -574,6 +587,90 @@ impl<'db> SemanticsImpl<'db> {
         });
         InFile::new(file_id, node)
     }
+
+    pub fn is_unsafe_method_call(&self, method_call_expr: ast::MethodCallExpr) -> bool {
+        method_call_expr
+            .expr()
+            .and_then(|expr| {
+                let field_expr = if let ast::Expr::FieldExpr(field_expr) = expr {
+                    field_expr
+                } else {
+                    return None;
+                };
+                let ty = self.type_of_expr(&field_expr.expr()?)?;
+                if !ty.is_packed(self.db) {
+                    return None;
+                }
+
+                let func = self.resolve_method_call(&method_call_expr).map(Function::from)?;
+                let is_unsafe = func.has_self_param(self.db)
+                    && matches!(func.params(self.db).first(), Some(TypeRef::Reference(..)));
+                Some(is_unsafe)
+            })
+            .unwrap_or(false)
+    }
+
+    pub fn is_unsafe_ref_expr(&self, ref_expr: &ast::RefExpr) -> bool {
+        ref_expr
+            .expr()
+            .and_then(|expr| {
+                let field_expr = match expr {
+                    ast::Expr::FieldExpr(field_expr) => field_expr,
+                    _ => return None,
+                };
+                let expr = field_expr.expr()?;
+                self.type_of_expr(&expr)
+            })
+            // Binding a reference to a packed type is possibly unsafe.
+            .map(|ty| ty.is_packed(self.db))
+            .unwrap_or(false)
+
+        // FIXME This needs layout computation to be correct. It will highlight
+        // more than it should with the current implementation.
+    }
+
+    pub fn is_unsafe_ident_pat(&self, ident_pat: &ast::IdentPat) -> bool {
+        if !ident_pat.ref_token().is_some() {
+            return false;
+        }
+
+        ident_pat
+            .syntax()
+            .parent()
+            .and_then(|parent| {
+                // `IdentPat` can live under `RecordPat` directly under `RecordPatField` or
+                // `RecordPatFieldList`. `RecordPatField` also lives under `RecordPatFieldList`,
+                // so this tries to lookup the `IdentPat` anywhere along that structure to the
+                // `RecordPat` so we can get the containing type.
+                let record_pat = ast::RecordPatField::cast(parent.clone())
+                    .and_then(|record_pat| record_pat.syntax().parent())
+                    .or_else(|| Some(parent.clone()))
+                    .and_then(|parent| {
+                        ast::RecordPatFieldList::cast(parent)?
+                            .syntax()
+                            .parent()
+                            .and_then(ast::RecordPat::cast)
+                    });
+
+                // If this doesn't match a `RecordPat`, fallback to a `LetStmt` to see if
+                // this is initialized from a `FieldExpr`.
+                if let Some(record_pat) = record_pat {
+                    self.type_of_pat(&ast::Pat::RecordPat(record_pat))
+                } else if let Some(let_stmt) = ast::LetStmt::cast(parent) {
+                    let field_expr = match let_stmt.initializer()? {
+                        ast::Expr::FieldExpr(field_expr) => field_expr,
+                        _ => return None,
+                    };
+
+                    self.type_of_expr(&field_expr.expr()?)
+                } else {
+                    None
+                }
+            })
+            // Binding a reference to a packed type is possibly unsafe.
+            .map(|ty| ty.is_packed(self.db))
+            .unwrap_or(false)
+    }
 }
 
 pub trait ToDef: AstNode + Clone {