Don't try to narrow type of a symbol within RHS of its declaration

src/compiler/checker.ts

@@ -30838,7 +30838,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     function getNarrowedTypeOfSymbol(symbol: Symbol, location: Identifier) {
         const type = getTypeOfSymbol(symbol);
         const declaration = symbol.valueDeclaration;
-        if (declaration) {
+        if (declaration && !textRangeContainsPositionInclusive(getRootDeclaration(declaration), location.pos)) {
             // If we have a non-rest binding element with no initializer declared as a const variable or a const-like
             // parameter (a parameter for which there are no assignments in the function body), and if the parent type
             // for the destructuring is a union type, one or more of the binding elements may represent discriminant
@@ -30866,23 +30866,18 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 const parent = declaration.parent.parent;
                 const rootDeclaration = getRootDeclaration(parent);
                 if (rootDeclaration.kind === SyntaxKind.VariableDeclaration && getCombinedNodeFlagsCached(rootDeclaration) & NodeFlags.Constant || rootDeclaration.kind === SyntaxKind.Parameter) {
-                    const links = getNodeLinks(parent);
-                    if (!(links.flags & NodeCheckFlags.InCheckIdentifier)) {
-                        links.flags |= NodeCheckFlags.InCheckIdentifier;
-                        const parentType = getTypeForBindingElementParent(parent, CheckMode.Normal);
-                        const parentTypeConstraint = parentType && mapType(parentType, getBaseConstraintOrType);
-                        links.flags &= ~NodeCheckFlags.InCheckIdentifier;
-                        if (parentTypeConstraint && parentTypeConstraint.flags & TypeFlags.Union && !(rootDeclaration.kind === SyntaxKind.Parameter && isSomeSymbolAssigned(rootDeclaration))) {
-                            const pattern = declaration.parent;
-                            const narrowedType = getFlowTypeOfReference(pattern, parentTypeConstraint, parentTypeConstraint, /*flowContainer*/ undefined, location.flowNode);
-                            if (narrowedType.flags & TypeFlags.Never) {
-                                return neverType;
-                            }
-                            // Destructurings are validated against the parent type elsewhere. Here we disable tuple bounds
-                            // checks because the narrowed type may have lower arity than the full parent type. For example,
-                            // for the declaration [x, y]: [1, 2] | [3], we may have narrowed the parent type to just [3].
-                            return getBindingElementTypeFromParentType(declaration, narrowedType, /*noTupleBoundsCheck*/ true);
+                    const parentType = getTypeForBindingElementParent(parent, CheckMode.Normal);
+                    const parentTypeConstraint = parentType && mapType(parentType, getBaseConstraintOrType);
+                    if (parentTypeConstraint && parentTypeConstraint.flags & TypeFlags.Union && !(rootDeclaration.kind === SyntaxKind.Parameter && isSomeSymbolAssigned(rootDeclaration))) {
+                        const pattern = declaration.parent;
+                        const narrowedType = getFlowTypeOfReference(pattern, parentTypeConstraint, parentTypeConstraint, /*flowContainer*/ undefined, location.flowNode);
+                        if (narrowedType.flags & TypeFlags.Never) {
+                            return neverType;
                         }
+                        // Destructurings are validated against the parent type elsewhere. Here we disable tuple bounds
+                        // checks because the narrowed type may have lower arity than the full parent type. For example,
+                        // for the declaration [x, y]: [1, 2] | [3], we may have narrowed the parent type to just [3].
+                        return getBindingElementTypeFromParentType(declaration, narrowedType, /*noTupleBoundsCheck*/ true);
                     }
                 }
             }

src/compiler/types.ts

@@ -6240,8 +6240,7 @@ export const enum NodeCheckFlags {
     ConstructorReference                     = 1 << 29,  // Binding to a class constructor inside of the class's body.
     ContainsClassWithPrivateIdentifiers      = 1 << 20,  // Marked on all block-scoped containers containing a class with private identifiers.
     ContainsSuperPropertyInStaticInitializer = 1 << 21,  // Marked on all block-scoped containers containing a static initializer with 'super.x' or 'super[x]'.
-    InCheckIdentifier                        = 1 << 22,
-    PartiallyTypeChecked                     = 1 << 23,  // Node has been partially type checked
+    PartiallyTypeChecked                     = 1 << 22,  // Node has been partially type checked
 
     /** These flags are LazyNodeCheckFlags and can be calculated lazily by `hasNodeCheckFlag` */
     LazyFlags = SuperInstance

tests/baselines/reference/dependentDestructuredVariablesRefereinceInDeclaration1.errors.txt

@@ -0,0 +1,148 @@
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(4,9): error TS2322: Type '{ c: number; f: any; }' is not assignable to type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(4,11): error TS2339: Property 'c' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(4,14): error TS2339: Property 'f' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(4,14): error TS7022: 'f' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(4,45): error TS2448: Block-scoped variable 'f' used before its declaration.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(9,9): error TS2322: Type '{ c: number; f: () => any; }' is not assignable to type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(9,11): error TS2339: Property 'c' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(9,14): error TS2339: Property 'f' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(14,9): error TS2322: Type '{ c: number; f: number; g: number; }' is not assignable to type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(14,11): error TS2339: Property 'c' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(14,14): error TS2339: Property 'f' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(14,17): error TS2339: Property 'g' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(20,9): error TS2322: Type '{ c: number; f: number; }' is not assignable to type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(20,11): error TS2339: Property 'c' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(20,14): error TS2339: Property 'f' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(20,14): error TS2451: Cannot redeclare block-scoped variable 'f'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(20,17): error TS2339: Property 'f' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(20,17): error TS2451: Cannot redeclare block-scoped variable 'f'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(25,9): error TS2322: Type '{ c: number; f: number; }' is not assignable to type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(25,11): error TS2339: Property 'c' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(25,14): error TS2339: Property 'f' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(25,17): error TS2339: Property 'f' does not exist on type 'string | number'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(30,14): error TS7022: 'f' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(30,71): error TS2448: Block-scoped variable 'f' used before its declaration.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(58,14): error TS2451: Cannot redeclare block-scoped variable 'f'.
+dependentDestructuredVariablesRefereinceInDeclaration1.ts(58,17): error TS2451: Cannot redeclare block-scoped variable 'f'.
+
+
+==== dependentDestructuredVariablesRefereinceInDeclaration1.ts (26 errors) ====
+    // https://github.com/microsoft/TypeScript/issues/62993
+
+    {
+      const { c, f }: string | number = { c: 0, f };
+            ~~~~~~~~
+!!! error TS2322: Type '{ c: number; f: any; }' is not assignable to type 'string | number'.
+              ~
+!!! error TS2339: Property 'c' does not exist on type 'string | number'.
+                 ~
+!!! error TS2339: Property 'f' does not exist on type 'string | number'.
+                 ~
+!!! error TS7022: 'f' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
+                                                ~
+!!! error TS2448: Block-scoped variable 'f' used before its declaration.
+!!! related TS2728 dependentDestructuredVariablesRefereinceInDeclaration1.ts:4:14: 'f' is declared here.
+      f;
+    }
+
+    {
+      const { c, f }: string | number = { c: 0, f: () => f };
+            ~~~~~~~~
+!!! error TS2322: Type '{ c: number; f: () => any; }' is not assignable to type 'string | number'.
+              ~
+!!! error TS2339: Property 'c' does not exist on type 'string | number'.
+                 ~
+!!! error TS2339: Property 'f' does not exist on type 'string | number'.
+      f;
+    }
+
+    {
+      const { c, f, g = f }: string | number = { c: 0, f: 0, g: 0 };
+            ~~~~~~~~~~~~~~~
+!!! error TS2322: Type '{ c: number; f: number; g: number; }' is not assignable to type 'string | number'.
+              ~
+!!! error TS2339: Property 'c' does not exist on type 'string | number'.
+                 ~
+!!! error TS2339: Property 'f' does not exist on type 'string | number'.
+                    ~
+!!! error TS2339: Property 'g' does not exist on type 'string | number'.
+      f;
+      g;
+    }
+
+    {
+      const { c, f, f }: string | number = { c: 0, f: 0 };
+            ~~~~~~~~~~~
+!!! error TS2322: Type '{ c: number; f: number; }' is not assignable to type 'string | number'.
+              ~
+!!! error TS2339: Property 'c' does not exist on type 'string | number'.
+                 ~
+!!! error TS2339: Property 'f' does not exist on type 'string | number'.
+                 ~
+!!! error TS2451: Cannot redeclare block-scoped variable 'f'.
+                    ~
+!!! error TS2339: Property 'f' does not exist on type 'string | number'.
+                    ~
+!!! error TS2451: Cannot redeclare block-scoped variable 'f'.
+      f;
+    }
+
+    {
+      const { c, f, f: g }: string | number = { c: 0, f: 0 };
+            ~~~~~~~~~~~~~~
+!!! error TS2322: Type '{ c: number; f: number; }' is not assignable to type 'string | number'.
+              ~
+!!! error TS2339: Property 'c' does not exist on type 'string | number'.
+                 ~
+!!! error TS2339: Property 'f' does not exist on type 'string | number'.
+                    ~
+!!! error TS2339: Property 'f' does not exist on type 'string | number'.
+      g;
+    }
+
+    {
+      const { c, f }: { c: 0; f: number } | { c: 1; f: string } = { c: 0, f };
+                 ~
+!!! error TS7022: 'f' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
+                                                                          ~
+!!! error TS2448: Block-scoped variable 'f' used before its declaration.
+!!! related TS2728 dependentDestructuredVariablesRefereinceInDeclaration1.ts:30:14: 'f' is declared here.
+      f;
+    }
+
+    {
+      const { c, f }: { c: 0; f: () => unknown } | { c: 1; f: string } = {
+        c: 0,
+        f: () => f,
+      };
+      f;
+    }
+
+    {
+      const {
+        c,
+        f,
+        g = f,
+      }:
+        | { c: 0; f: bigint; g?: bigint | number }
+        | { c: 1; f: number; g: string } = {
+        c: 0,
+        f: 10n,
+      };
+      f;
+      g;
+    }
+
+    {
+      const { c, f, f }: { c: 0; f: number } | { c: 1; f: string } = { c: 0, f: 0 };
+                 ~
+!!! error TS2451: Cannot redeclare block-scoped variable 'f'.
+                    ~
+!!! error TS2451: Cannot redeclare block-scoped variable 'f'.
+      f;
+    }
+
+    {
+      const { c, f, f: g }: { c: 0; f: number } | { c: 1; f: string } = { c: 0, f: 0 };
+      g;
+    }