Merge pull request #9167 from Microsoft/make-unions-and-intersections-of-readonly-properties-readonly

Unions and intersections of readonly properties are now also readonly

Author: sandersn

src/compiler/checker.ts

@@ -4233,6 +4233,7 @@ namespace ts {
             let props: Symbol[];
             // Flags we want to propagate to the result if they exist in all source symbols
             let commonFlags = (containingType.flags & TypeFlags.Intersection) ? SymbolFlags.Optional : SymbolFlags.None;
+            let isReadonly = false;
             for (const current of types) {
                 const type = getApparentType(current);
                 if (type !== unknownType) {
@@ -4245,6 +4246,9 @@ namespace ts {
                         else if (!contains(props, prop)) {
                             props.push(prop);
                         }
+                        if (isReadonlySymbol(prop)) {
+                            isReadonly = true;
+                        }
                     }
                     else if (containingType.flags & TypeFlags.Union) {
                         // A union type requires the property to be present in all constituent types
@@ -4274,6 +4278,7 @@ namespace ts {
                 name);
             result.containingType = containingType;
             result.declarations = declarations;
+            result.isReadonly = isReadonly;
             result.type = containingType.flags & TypeFlags.Union ? getUnionType(propTypes) : getIntersectionType(propTypes);
             return result;
         }
@@ -12204,7 +12209,9 @@ namespace ts {
             // Variables declared with 'const'
             // Get accessors without matching set accessors
             // Enum members
-            return symbol.flags & SymbolFlags.Property && (getDeclarationFlagsFromSymbol(symbol) & NodeFlags.Readonly) !== 0 ||
+            // Unions and intersections of the above (unions and intersections eagerly set isReadonly on creation)
+            return symbol.isReadonly ||
+                symbol.flags & SymbolFlags.Property && (getDeclarationFlagsFromSymbol(symbol) & NodeFlags.Readonly) !== 0 ||
                 symbol.flags & SymbolFlags.Variable && (getDeclarationFlagsFromSymbol(symbol) & NodeFlags.Const) !== 0 ||
                 symbol.flags & SymbolFlags.Accessor && !(symbol.flags & SymbolFlags.SetAccessor) ||
                 (symbol.flags & SymbolFlags.EnumMember) !== 0;

src/compiler/types.ts

@@ -2122,6 +2122,7 @@ namespace ts {
         members?: SymbolTable;                  // Class, interface or literal instance members
         exports?: SymbolTable;                  // Module exports
         globalExports?: SymbolTable;            // Conditional global UMD exports
+        /* @internal */ isReadonly?: boolean;   // readonly? (set only for intersections and unions)
         /* @internal */ id?: number;            // Unique id (used to look up SymbolLinks)
         /* @internal */ mergeId?: number;       // Merge id (used to look up merged symbol)
         /* @internal */ parent?: Symbol;        // Parent symbol

tests/baselines/reference/intersectionTypeReadonly.errors.txt

@@ -0,0 +1,44 @@
+tests/cases/conformance/types/intersection/intersectionTypeReadonly.ts(17,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/conformance/types/intersection/intersectionTypeReadonly.ts(19,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/conformance/types/intersection/intersectionTypeReadonly.ts(21,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/conformance/types/intersection/intersectionTypeReadonly.ts(23,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/conformance/types/intersection/intersectionTypeReadonly.ts(25,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+
+
+==== tests/cases/conformance/types/intersection/intersectionTypeReadonly.ts (5 errors) ====
+    interface Base {
+        readonly value: number;
+    }
+    interface Identical {
+        readonly value: number;
+    }
+    interface Mutable {
+        value: number;
+    }
+    interface DifferentType {
+        readonly value: string;
+    }
+    interface DifferentName {
+        readonly other: number;
+    }
+    let base: Base;
+    base.value = 12 // error, lhs can't be a readonly property
+    ~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    let identical: Base & Identical;
+    identical.value = 12; // error, lhs can't be a readonly property
+    ~~~~~~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    let mutable: Base & Mutable;
+    mutable.value = 12; // error, lhs can't be a readonly property
+    ~~~~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    let differentType: Base & DifferentType;
+    differentType.value = 12; // error, lhs can't be a readonly property
+    ~~~~~~~~~~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    let differentName: Base & DifferentName;
+    differentName.value = 12; // error, property 'value' doesn't exist
+    ~~~~~~~~~~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    

tests/baselines/reference/intersectionTypeReadonly.js

@@ -0,0 +1,39 @@
+//// [intersectionTypeReadonly.ts]
+interface Base {
+    readonly value: number;
+}
+interface Identical {
+    readonly value: number;
+}
+interface Mutable {
+    value: number;
+}
+interface DifferentType {
+    readonly value: string;
+}
+interface DifferentName {
+    readonly other: number;
+}
+let base: Base;
+base.value = 12 // error, lhs can't be a readonly property
+let identical: Base & Identical;
+identical.value = 12; // error, lhs can't be a readonly property
+let mutable: Base & Mutable;
+mutable.value = 12; // error, lhs can't be a readonly property
+let differentType: Base & DifferentType;
+differentType.value = 12; // error, lhs can't be a readonly property
+let differentName: Base & DifferentName;
+differentName.value = 12; // error, property 'value' doesn't exist
+
+
+//// [intersectionTypeReadonly.js]
+var base;
+base.value = 12; // error, lhs can't be a readonly property
+var identical;
+identical.value = 12; // error, lhs can't be a readonly property
+var mutable;
+mutable.value = 12; // error, lhs can't be a readonly property
+var differentType;
+differentType.value = 12; // error, lhs can't be a readonly property
+var differentName;
+differentName.value = 12; // error, property 'value' doesn't exist

tests/baselines/reference/unionTypeReadonly.errors.txt

@@ -0,0 +1,45 @@
+tests/cases/conformance/types/union/unionTypeReadonly.ts(17,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/conformance/types/union/unionTypeReadonly.ts(19,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/conformance/types/union/unionTypeReadonly.ts(21,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/conformance/types/union/unionTypeReadonly.ts(23,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/conformance/types/union/unionTypeReadonly.ts(25,15): error TS2339: Property 'value' does not exist on type 'Base | DifferentName'.
+
+
+==== tests/cases/conformance/types/union/unionTypeReadonly.ts (5 errors) ====
+    interface Base {
+        readonly value: number;
+    }
+    interface Identical {
+        readonly value: number;
+    }
+    interface Mutable {
+        value: number;
+    }
+    interface DifferentType {
+        readonly value: string;
+    }
+    interface DifferentName {
+        readonly other: number;
+    }
+    let base: Base;
+    base.value = 12 // error, lhs can't be a readonly property
+    ~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    let identical: Base | Identical;
+    identical.value = 12; // error, lhs can't be a readonly property
+    ~~~~~~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    let mutable: Base | Mutable;
+    mutable.value = 12; // error, lhs can't be a readonly property
+    ~~~~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    let differentType: Base | DifferentType;
+    differentType.value = 12; // error, lhs can't be a readonly property
+    ~~~~~~~~~~~~~~~~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+    let differentName: Base | DifferentName;
+    differentName.value = 12; // error, property 'value' doesn't exist
+                  ~~~~~
+!!! error TS2339: Property 'value' does not exist on type 'Base | DifferentName'.
+    
+    

tests/baselines/reference/unionTypeReadonly.js

@@ -0,0 +1,40 @@
+//// [unionTypeReadonly.ts]
+interface Base {
+    readonly value: number;
+}
+interface Identical {
+    readonly value: number;
+}
+interface Mutable {
+    value: number;
+}
+interface DifferentType {
+    readonly value: string;
+}
+interface DifferentName {
+    readonly other: number;
+}
+let base: Base;
+base.value = 12 // error, lhs can't be a readonly property
+let identical: Base | Identical;
+identical.value = 12; // error, lhs can't be a readonly property
+let mutable: Base | Mutable;
+mutable.value = 12; // error, lhs can't be a readonly property
+let differentType: Base | DifferentType;
+differentType.value = 12; // error, lhs can't be a readonly property
+let differentName: Base | DifferentName;
+differentName.value = 12; // error, property 'value' doesn't exist
+
+
+
+//// [unionTypeReadonly.js]
+var base;
+base.value = 12; // error, lhs can't be a readonly property
+var identical;
+identical.value = 12; // error, lhs can't be a readonly property
+var mutable;
+mutable.value = 12; // error, lhs can't be a readonly property
+var differentType;
+differentType.value = 12; // error, lhs can't be a readonly property
+var differentName;
+differentName.value = 12; // error, property 'value' doesn't exist

tests/cases/conformance/types/intersection/intersectionTypeReadonly.ts

@@ -0,0 +1,25 @@
+interface Base {
+    readonly value: number;
+}
+interface Identical {
+    readonly value: number;
+}
+interface Mutable {
+    value: number;
+}
+interface DifferentType {
+    readonly value: string;
+}
+interface DifferentName {
+    readonly other: number;
+}
+let base: Base;
+base.value = 12 // error, lhs can't be a readonly property
+let identical: Base & Identical;
+identical.value = 12; // error, lhs can't be a readonly property
+let mutable: Base & Mutable;
+mutable.value = 12; // error, lhs can't be a readonly property
+let differentType: Base & DifferentType;
+differentType.value = 12; // error, lhs can't be a readonly property
+let differentName: Base & DifferentName;
+differentName.value = 12; // error, property 'value' doesn't exist

tests/cases/conformance/types/union/unionTypeReadonly.ts

@@ -0,0 +1,26 @@
+interface Base {
+    readonly value: number;
+}
+interface Identical {
+    readonly value: number;
+}
+interface Mutable {
+    value: number;
+}
+interface DifferentType {
+    readonly value: string;
+}
+interface DifferentName {
+    readonly other: number;
+}
+let base: Base;
+base.value = 12 // error, lhs can't be a readonly property
+let identical: Base | Identical;
+identical.value = 12; // error, lhs can't be a readonly property
+let mutable: Base | Mutable;
+mutable.value = 12; // error, lhs can't be a readonly property
+let differentType: Base | DifferentType;
+differentType.value = 12; // error, lhs can't be a readonly property
+let differentName: Base | DifferentName;
+differentName.value = 12; // error, property 'value' doesn't exist
+