asgerf · Oct 23, 2026 · Oct 23, 2026 · Oct 23, 2026 · Oct 23, 2026 · Oct 23, 2026
@@ -534,7 +534,7 @@ named:
     name_node: identifier
     accessor_kind: accessor_kind
     parameter*: parameter
-    type?: expr
+    return_type?: expr
     body?: block
 
   # "get", "set", or a language-specific kind like "didSet"

@@ -12,15 +12,15 @@ struct SwiftContext {
     /// `variableDecl` rule before translating the accessor block; read by the
     /// inner `accessorDecl` rules to name each `accessor_declaration`.
     property_name_node: Option<yeast::Id>,
-    /// Translated type node for the property type. Set (for computed
-    /// properties) by the accessor-bearing `variableDecl` rule; read by the
-    /// inner `accessorDecl` rules. Left `None` for stored properties with
-    /// observers, so their `willSet`/`didSet` accessors carry no type.
+    /// Translated type node for the property type. Set by the
+    /// accessor-bearing `variableDecl` rule; read by the inner `accessorDecl`
+    /// rules for both the accessor type and its `newValue`/`oldValue`
+    /// parameter type.
     property_type: Option<yeast::Id>,
     /// Translated outer modifiers to attach to each child of a flattening
-    /// outer rule — e.g. the `let`/`var` binding modifier on each
-    /// `patternBinding` of a `variableDecl`, or the binding modifier on each
-    /// accessor of a property.
+    /// outer rule — e.g. the `let`/`var` binding modifier, attributes and
+    /// modifiers (`static`, `public`, …) on each `patternBinding` of a
+    /// `variableDecl`, or on each accessor of a property.
     outer_modifiers: Vec<yeast::Id>,
     /// True when the current child of a flattening outer rule is not
     /// the first one — its inner rule should emit a
@@ -325,6 +325,8 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
         // block.
         rule!(
             (variableDecl
+                attributes: _* @attrs
+                modifiers: _* @mods
                 bindingSpecifier: @@spec
                 bindings: (patternBinding
                     pattern: (identifierPattern identifier: @@name)
@@ -333,8 +335,10 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
             =>
             (accessor_declaration
                 modifier: (modifier #{spec})
+                modifier: {attrs}
+                modifier: {mods}
                 name_node: (identifier #{name})
-                type: {ty}
+                return_type: {ty}
                 accessor_kind: {ctx.literal_at_start_of("accessor_kind", "get", body)}
                 body: {body})
         ),
@@ -345,16 +349,18 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
         //  * With an initializer (`var x: T = e { willSet {…} didSet {…} }`) it is
         //    a *stored* property with observers: emit the backing
         //    `variable_declaration` first, then one `accessor_declaration` per
-        //    observer (observers carry no type).
+        //    observer.
         //  * Without an initializer (`var v: T { get set }`, incl. protocol
-        //    requirements) it is a *computed* property: no backing variable; the
-        //    type is published so the get/set accessors carry it.
+        //    requirements) it is a *computed* property: no backing variable.
         //
-        // In both cases the first emitted declaration is unchained and every
+        // In both cases the type is published so every accessor carries it, and
+        // the first emitted declaration is unchained and every
         // subsequent one is tagged `chained_declaration` (the `!result.is_empty()`
         // test). Must precede the plain `variableDecl` rules.
         rule!(
             (variableDecl
+                attributes: _* @attrs
+                modifiers: _* @mods
                 bindingSpecifier: @@spec
                 bindings: (patternBinding
                     pattern: (identifierPattern identifier: @@name)
@@ -363,8 +369,14 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                     accessorBlock: (accessorBlock accessors: (accessorDecl)+ @@accessors)))
             =>
             member* {
-                ctx.outer_modifiers = vec![tree!((modifier #{spec}))];
+                // The binding (`let`/`var`) leads, then attributes then modifiers,
+                // matching the plain `variableDecl` rule.
+                ctx.outer_modifiers = std::iter::once(tree!((modifier #{spec})))
+                    .chain(attrs)
+                    .chain(mods)
+                    .collect();
                 ctx.property_name_node = Some(tree!((identifier #{name})));
+                ctx.property_type = Some(ty);
                 let mut result = Vec::new();
                 if let Some(val) = val {
                     // Stored property with observers: the initializer is not part
@@ -380,9 +392,6 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                             type: {ty}
                             value: {val})
                     ));
-                } else {
-                    // Computed property: the accessors carry the type.
-                    ctx.property_type = Some(ty);
                 }
                 for acc in accessors.into_iter() {
                     ctx.is_chained = !result.is_empty();
@@ -392,28 +401,56 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
             }
         ),
         // Each `accessorDecl` becomes an `accessor_declaration`, reading the
-        // property name/type and the binding/chained modifiers from `ctx`. The
+        // property name/type and the modifiers from `ctx`. The
         // accessor kind comes straight from the specifier keyword
         // (`get`/`set`/`willSet`/`didSet`). The body is optional: a body-bearing
         // accessor (a computed getter/setter, or a `willSet`/`didSet` observer)
-        // carries the binding modifier and a translated body, whereas a bodyless
-        // one (a protocol requirement) carries neither. The property context is
+        // has a translated body, whereas a bodyless one (a protocol requirement)
+        // has none. The property context is
         // read out *before* translating the body, which resets `ctx` so the
         // accessor's context does not leak into the body subtree.
+        //
+        // `set` and `willSet` accessors get a parameter holding the incoming
+        // value, and `didSet` gets one holding the previous value. It is named
+        // explicitly (`set(v)`) or else implicitly `newValue`/`oldValue`.
         rule!(
-            (accessorDecl accessorSpecifier: @@spec body: _? @@body)
+            (accessorDecl
+                accessorSpecifier: @@spec
+                parameters: (accessorParameters name: @@param_name)?
+                body: _? @@body)
             =>
             accessor_declaration {
-                let binding = if body.is_some() {
-                    ctx.outer_modifiers.clone()
-                } else {
-                    Vec::new()
+                let spec_text = ctx.source_text(spec);
+                let implicit_param_name = match spec_text.as_str() {
+                    "set" | "willSet" => Some("newValue"),
+                    "didSet" => Some("oldValue"),
+                    _ => None,
                 };
+                let param_ty = ctx.property_type;
+                let param = match (param_name, implicit_param_name) {
+                    (Some(n), _) => {
+                        Some(tree!((parameter pattern: (identifier #{n}) type: {param_ty})))
+                    }
+                    (None, Some(n)) => {
+                        let n = n.to_string();
+                        Some(tree!((parameter
+                            modifier: (modifier "generated")
+                            pattern: (identifier #{n} location: {spec})
+                            type: {param_ty}
+                            location: {spec})))
+                    }
+                    (None, None) => None,
+                };
+                let modifiers = ctx.outer_modifiers.clone();
                 let chained = chained_modifier(&mut ctx);
                 let name = ctx
                     .property_name_node
                     .ok_or("accessor outside property context")?;
-                let ty = ctx.property_type;
+                let return_ty = if spec_text == "get" {
+                    ctx.property_type
+                } else {
+                    None
+                };
                 let body = match body {
                     Some(block) => {
                         ctx.reset();
@@ -422,11 +459,12 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                     None => None,
                 };
                 tree!((accessor_declaration
-                    modifier: {binding}
+                    modifier: {modifiers}
                     modifier: {chained}
                     name_node: {name}
-                    type: {ty}
+                    return_type: {return_ty}
                     accessor_kind: (accessor_kind #{spec})
+                    parameter: {param}
                     body: {body}
                     location: {spec}
                     location: {body}))

@@ -100,7 +100,7 @@ top_level source="var p: Int {\n  ⟨body⟩\n}"
           modifier: modifier "var" source="var" (external)
           name_node: identifier "p" source="p" (external)
           accessor_kind: accessor_kind "get" source="get"
-          type: identifier "Int" source="Int" (external)
+          return_type: identifier "Int" source="Int" (external)
           body:
             block source="{\n    ⟨stmt⟩\n  }"
               stmt:

@@ -113,11 +113,11 @@ top_level source="⟨body⟩"
               modifier: modifier "var" source="var"
               pattern: identifier "h" source="h"
               type: identifier "Double" source="Double"
-            accessor_declaration source="⟨modifier⟩ ⟨name_node⟩: ⟨type⟩ ⟨body⟩"
+            accessor_declaration source="⟨modifier⟩ ⟨name_node⟩: ⟨return_type⟩ ⟨body⟩"
               modifier: modifier "var" source="var"
               name_node: identifier "area" source="area"
               accessor_kind: accessor_kind "get" source=""
-              type: identifier "Double" source="Double"
+              return_type: identifier "Double" source="Double"
               body:
                 block source="{\n    ⟨stmt⟩\n  }"
                   stmt:

@@ -120,19 +120,23 @@ top_level source="⟨body⟩"
               modifier: modifier "var" source="var" (external)
               name_node: identifier "v" source="v" (external)
               accessor_kind: accessor_kind "get" source="get"
-              type: identifier "Int" source="Int" (external)
+              return_type: identifier "Int" source="Int" (external)
               body:
                 block source="{ ⟨stmt⟩ }"
                   stmt:
                     return_expr source="return ⟨value⟩"
                       value: identifier "_v" source="_v"
-            accessor_declaration source="⟨accessor_kind⟩ ⟨body⟩"
+            accessor_declaration source="⟨accessor_kind⟩⟨parameter⟩ ⟨body⟩"
               modifier:
                 modifier "var" source="var" (external)
                 modifier "chained_declaration" source=""
               name_node: identifier "v" source="v" (external)
               accessor_kind: accessor_kind "set" source="set"
-              type: identifier "Int" source="Int" (external)
+              parameter:
+                parameter source="⟨pattern⟩"
+                  modifier: modifier "generated" source=""
+                  type: identifier "Int" source="Int" (external)
+                  pattern: identifier "newValue" source="set"
               body:
                 block source="{ ⟨stmt⟩ }"
                   stmt:

@@ -111,19 +111,28 @@ top_level source="⟨body⟩"
           name_node: identifier "P" source="P"
           member:
             accessor_declaration source="⟨accessor_kind⟩"
+              modifier: modifier "var" source="var" (external)
               name_node: identifier "foo" source="foo" (external)
               accessor_kind: accessor_kind "get" source="get"
-              type: identifier "Int" source="Int" (external)
+              return_type: identifier "Int" source="Int" (external)
             accessor_declaration source="⟨accessor_kind⟩"
+              modifier: modifier "var" source="var" (external)
               name_node: identifier "bar" source="bar" (external)
               accessor_kind: accessor_kind "get" source="get"
-              type: identifier "String" source="String" (external)
-            accessor_declaration source="⟨accessor_kind⟩"
-              modifier: modifier "chained_declaration" source=""
+              return_type: identifier "String" source="String" (external)
+            accessor_declaration source="⟨accessor_kind⟩⟨parameter⟩"
+              modifier:
+                modifier "var" source="var" (external)
+                modifier "chained_declaration" source=""
               name_node: identifier "bar" source="bar" (external)
               accessor_kind: accessor_kind "set" source="set"
-              type: identifier "String" source="String" (external)
+              parameter:
+                parameter source="⟨pattern⟩"
+                  modifier: modifier "generated" source=""
+                  type: identifier "String" source="String" (external)
+                  pattern: identifier "newValue" source="set"
             accessor_declaration source="⟨accessor_kind⟩"
+              modifier: modifier "var" source="var" (external)
               name_node: identifier "count" source="count" (external)
               accessor_kind: accessor_kind "get" source="get"
-              type: identifier "Int" source="Int" (external)
+              return_type: identifier "Int" source="Int" (external)
@@ -110,12 +110,17 @@ top_level source="⟨body⟩"
               pattern: identifier "x" source="x"
               type: identifier "Int" source="Int"
               value: int_literal "0" source="0"
-            accessor_declaration source="⟨accessor_kind⟩ ⟨body⟩"
+            accessor_declaration source="⟨accessor_kind⟩⟨parameter⟩ ⟨body⟩"
               modifier:
                 modifier "var" source="var" (external)
                 modifier "chained_declaration" source=""
               name_node: identifier "x" source="x" (external)
               accessor_kind: accessor_kind "willSet" source="willSet"
+              parameter:
+                parameter source="⟨pattern⟩"
+                  modifier: modifier "generated" source=""
+                  type: identifier "Int" source="Int" (external)
+                  pattern: identifier "newValue" source="willSet"
               body:
                 block source="{ ⟨stmt⟩ }"
                   stmt:
@@ -124,12 +129,17 @@ top_level source="⟨body⟩"
                       argument:
                         argument source="⟨value⟩"
                           value: identifier "newValue" source="newValue"
-            accessor_declaration source="⟨accessor_kind⟩ ⟨body⟩"
+            accessor_declaration source="⟨accessor_kind⟩⟨parameter⟩ ⟨body⟩"
               modifier:
                 modifier "var" source="var" (external)
                 modifier "chained_declaration" source=""
               name_node: identifier "x" source="x" (external)
               accessor_kind: accessor_kind "didSet" source="didSet"
+              parameter:
+                parameter source="⟨pattern⟩"
+                  modifier: modifier "generated" source=""
+                  type: identifier "Int" source="Int" (external)
+                  pattern: identifier "oldValue" source="didSet"
               body:
                 block source="{ ⟨stmt⟩ }"
                   stmt:

@@ -5,6 +5,10 @@ private import codeql.dataflow.internal.DataFlowImplConsistency
 module ConsistencyInput implements InputSig<Location, DataFlowInput> {
   predicate argHasPostUpdateExclude(DataFlowInput::ArgumentNode n) {
     not exists(n.getBasicBlock()) // ignore unreachable data flow nodes
+    or
+    // The RHS value passed into a setter call technically needs a post-update node
+    // because it's an argument to a call, but this rarely matters in practice.
+    n.isIncomingValue(any(DataFlowCall c).asSetterCall())
   }
 
   predicate reverseReadExclude(DataFlow::Node n) {

@@ -123,8 +123,10 @@ module Unified {
     /** Gets the node corresponding to the field `parameter`. */
     final override F::Parameter getAParameter() { result = this.getParameter(_) }
 
-    /** Gets the node corresponding to the field `type`. */
-    final F::Expr getType() { unified_accessor_declaration_type(this, result) }
+    /** Gets the node corresponding to the field `return_type`. */
+    final override F::Expr getReturnType() {
+      unified_accessor_declaration_return_type(this, result)
+    }
 
     /** Gets a field or child node of this node. */
     final override F::AstNode getAFieldOrChild() {
@@ -133,7 +135,7 @@ module Unified {
       unified_accessor_declaration_modifier(this, _, result) or
       unified_accessor_declaration_def(this, _, result) or
       unified_accessor_declaration_parameter(this, _, result) or
-      unified_accessor_declaration_type(this, result)
+      unified_accessor_declaration_return_type(this, result)
     }
   }
 
@@ -1624,7 +1626,7 @@ module Unified {
       or
       result = node.(AccessorDeclaration).getParameter(i) and name = "getParameter"
       or
-      result = node.(AccessorDeclaration).getType() and i = -1 and name = "getType"
+      result = node.(AccessorDeclaration).getReturnType() and i = -1 and name = "getReturnType"
       or
       result = node.(Argument).getModifier(i) and name = "getModifier"
       or

@@ -16,7 +16,7 @@ predicate isInTypeContext(Expr expr) {
   or
   expr = any(FunctionExpr n).getReturnType()
   or
-  expr = any(AccessorDeclaration n).getType()
+  expr = any(AccessorDeclaration n).getReturnType()
   or
   expr = any(Parameter n).getType()
   or

@@ -409,6 +409,7 @@ module Public {
       |
         decl instanceof VariableDeclaration or
         decl instanceof FunctionDeclaration or // treat functions as values
+        decl instanceof AccessorDeclaration or
         decl instanceof Parameter or
         decl instanceof ForEachStmt or
         decl instanceof PatternGuardExpr or
@@ -446,6 +447,25 @@ module Public {
     }
   }
 
+  private AccessorDeclaration getAnAccessor(LocalVariable v) {
+    v.getABinding() = result.getNameNode() and
+    (result instanceof GetterDeclaration or result instanceof SetterDeclaration)
+  }
+
+  /** A local variable defined by a getter/setter pair, which does not store a value on its own. */
+  final class ComputedLocalVariable extends LocalVariable {
+    ComputedLocalVariable() { exists(getAnAccessor(this)) }
+
+    /** Gets the getter or setter for this computed variable. */
+    AccessorDeclaration getAnAccessor() { result = getAnAccessor(this) }
+
+    /** Gets the getter for this computed variable. */
+    GetterDeclaration getGetterDeclaration() { result = getAnAccessor(this) }
+
+    /** Gets the setter for this computed variable. */
+    SetterDeclaration getSetterDeclaration() { result = getAnAccessor(this) }
+  }
+
   /** An access to a locally-declared name. */
   class LocalNameAccess extends PotentialLocalNameAccess {
     LocalNameAccess() { not this instanceof UnqualifiedMemberAccess }

@@ -81,6 +81,7 @@ predicate isInstanceMember(Member member) {
   (
     member instanceof VariableDeclaration or
     member instanceof FunctionDeclaration or
+    member instanceof AccessorDeclaration or
     member instanceof ConstructorDeclaration
   ) and
   exists(ClassLikeDeclaration cls | cls.getAMember() = member |