Check for constructor initialisation

Author: sandersn

src/compiler/checker.ts

@@ -29520,14 +29520,23 @@ namespace ts {
                         continue;
                     }
                     if (base.flags & SymbolFlags.PropertyOrAccessor && derived.flags & SymbolFlags.PropertyOrAccessor) {
-                        if (derived.flags & SymbolFlags.Property
+                        const uninitialized = find(derived.declarations, d => d.kind === SyntaxKind.PropertyDeclaration && !(d as PropertyDeclaration).initializer);
+                        if (uninitialized
+                            && derived.flags & SymbolFlags.Property
                             && !(derived.flags & SymbolFlags.Transient)
                             && !(baseDeclarationFlags & ModifierFlags.Abstract)
-                            && !(derivedDeclarationFlags & ModifierFlags.Ambient)
-                            && !derived.declarations.some(d => d.flags & NodeFlags.Ambient)
-                            && derived.declarations.some(d => d.kind === SyntaxKind.PropertyDeclaration && !(d as PropertyDeclaration).initializer)) {
-                            const errorMessage = Diagnostics.Class_0_defines_instance_member_property_1_so_extended_class_2_must_provide_an_initializer_with_this_override;
-                            error(getNameOfDeclaration(derived.valueDeclaration) || derived.valueDeclaration, errorMessage, typeToString(baseType), symbolToString(base), typeToString(type));
+                            && !(derivedDeclarationFlags & (ModifierFlags.Ambient | ModifierFlags.Abstract))
+                            && !derived.declarations.some(d => d.flags & NodeFlags.Ambient)) {
+                            const constructor = findConstructorDeclaration(getClassLikeDeclarationOfSymbol(type.symbol)!);
+                            const propName = (uninitialized as PropertyDeclaration).name;
+                            if ((uninitialized as PropertyDeclaration).exclamationToken
+                                || !constructor
+                                || !isIdentifier(propName)
+                                || !strictNullChecks
+                                || !isPropertyInitializedInConstructor(propName, type, constructor)) {
+                                const errorMessage = Diagnostics.Class_0_defines_instance_member_property_1_so_extended_class_2_must_provide_an_initializer_with_this_override;
+                                error(getNameOfDeclaration(derived.valueDeclaration) || derived.valueDeclaration, errorMessage, typeToString(baseType), symbolToString(base), typeToString(type));
+                            }
                         }
                         continue;
                     }

tests/baselines/reference/derivedUninitializedPropertyDeclaration.errors.txt

@@ -69,4 +69,17 @@ tests/cases/conformance/classes/propertyMemberDeclarations/derivedUninitializedP
 !!! error TS2610: Class 'E' defines instance member property 'p1', so extended class 'F' must provide an initializer with this override.
         declare p2: 'alpha'
     }
+    
+    class G extends E {
+        p1: 'z'
+        constructor() {
+            super()
+            this.p1 = 'z'
+        }
+    }
+    
+    abstract class H extends E {
+        abstract p1: 'a' | 'b' | 'c'
+        declare abstract p2: 'a' | 'b' | 'c'
+    }
 

tests/baselines/reference/derivedUninitializedPropertyDeclaration.js

@@ -40,6 +40,19 @@ class F extends E {
     p1!: 'z'
     declare p2: 'alpha'
 }
+
+class G extends E {
+    p1: 'z'
+    constructor() {
+        super()
+        this.p1 = 'z'
+    }
+}
+
+abstract class H extends E {
+    abstract p1: 'a' | 'b' | 'c'
+    declare abstract p2: 'a' | 'b' | 'c'
+}
 
 
 //// [derivedUninitializedPropertyDeclaration.js]
@@ -126,3 +139,19 @@ var F = /** @class */ (function (_super) {
     }
     return F;
 }(E));
+var G = /** @class */ (function (_super) {
+    __extends(G, _super);
+    function G() {
+        var _this = _super.call(this) || this;
+        _this.p1 = 'z';
+        return _this;
+    }
+    return G;
+}(E));
+var H = /** @class */ (function (_super) {
+    __extends(H, _super);
+    function H() {
+        return _super !== null && _super.apply(this, arguments) || this;
+    }
+    return H;
+}(E));

tests/baselines/reference/derivedUninitializedPropertyDeclaration.symbols

@@ -91,3 +91,32 @@ class F extends E {
 >p2 : Symbol(F.p2, Decl(derivedUninitializedPropertyDeclaration.ts, 38, 12))
 }
 
+class G extends E {
+>G : Symbol(G, Decl(derivedUninitializedPropertyDeclaration.ts, 40, 1))
+>E : Symbol(E, Decl(derivedUninitializedPropertyDeclaration.ts, 30, 1))
+
+    p1: 'z'
+>p1 : Symbol(G.p1, Decl(derivedUninitializedPropertyDeclaration.ts, 42, 19))
+
+    constructor() {
+        super()
+>super : Symbol(E, Decl(derivedUninitializedPropertyDeclaration.ts, 30, 1))
+
+        this.p1 = 'z'
+>this.p1 : Symbol(G.p1, Decl(derivedUninitializedPropertyDeclaration.ts, 42, 19))
+>this : Symbol(G, Decl(derivedUninitializedPropertyDeclaration.ts, 40, 1))
+>p1 : Symbol(G.p1, Decl(derivedUninitializedPropertyDeclaration.ts, 42, 19))
+    }
+}
+
+abstract class H extends E {
+>H : Symbol(H, Decl(derivedUninitializedPropertyDeclaration.ts, 48, 1))
+>E : Symbol(E, Decl(derivedUninitializedPropertyDeclaration.ts, 30, 1))
+
+    abstract p1: 'a' | 'b' | 'c'
+>p1 : Symbol(H.p1, Decl(derivedUninitializedPropertyDeclaration.ts, 50, 28))
+
+    declare abstract p2: 'a' | 'b' | 'c'
+>p2 : Symbol(H.p2, Decl(derivedUninitializedPropertyDeclaration.ts, 51, 32))
+}
+

tests/baselines/reference/derivedUninitializedPropertyDeclaration.types

@@ -95,3 +95,35 @@ class F extends E {
 >p2 : "alpha"
 }
 
+class G extends E {
+>G : G
+>E : E
+
+    p1: 'z'
+>p1 : "z"
+
+    constructor() {
+        super()
+>super() : void
+>super : typeof E
+
+        this.p1 = 'z'
+>this.p1 = 'z' : "z"
+>this.p1 : "z"
+>this : this
+>p1 : "z"
+>'z' : "z"
+    }
+}
+
+abstract class H extends E {
+>H : H
+>E : E
+
+    abstract p1: 'a' | 'b' | 'c'
+>p1 : "a" | "b" | "c"
+
+    declare abstract p2: 'a' | 'b' | 'c'
+>p2 : "a" | "b" | "c"
+}
+

tests/cases/conformance/classes/propertyMemberDeclarations/derivedUninitializedPropertyDeclaration.ts

@@ -40,3 +40,16 @@ class F extends E {
     p1!: 'z'
     declare p2: 'alpha'
 }
+
+class G extends E {
+    p1: 'z'
+    constructor() {
+        super()
+        this.p1 = 'z'
+    }
+}
+
+abstract class H extends E {
+    abstract p1: 'a' | 'b' | 'c'
+    declare abstract p2: 'a' | 'b' | 'c'
+}

tests/cases/fourslash/derivedTypeIndexerWithGenericConstraints.ts

@@ -13,7 +13,7 @@
 ////}
 
 ////class DbSet<TEntity extends Entity> extends BaseCollection<TEntity> { // error
-////    _itemsByKey: { [key: string]: TEntity; };
+////    _itemsByKey: { [key: string]: TEntity; } = {};
 ////}
 
 ////var a: BaseCollection<CollectionItem>;