get candidate discriminant property access in hasMatchingArgument

Author: gabritto

src/compiler/checker.ts

@@ -26743,7 +26743,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 if (
                     isOrContainsMatchingReference(reference, argument)
                     || optionalChainContainsReference(argument, reference)
-                    || isAccessExpression(argument) && isMatchingReference(reference, argument.expression)
+                    || getCandidateDiscriminantPropertyAccess(argument, reference)
                 ) {
                     return true;
                 }
@@ -26758,6 +26758,51 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return false;
     }
 
+    function getCandidateDiscriminantPropertyAccess(expr: Expression, reference: Node) {
+        if (isBindingPattern(reference) || isFunctionExpressionOrArrowFunction(reference) || isObjectLiteralMethod(reference)) {
+            // When the reference is a binding pattern or function or arrow expression, we are narrowing a pesudo-reference in
+            // getNarrowedTypeOfSymbol. An identifier for a destructuring variable declared in the same binding pattern or
+            // parameter declared in the same parameter list is a candidate.
+            if (isIdentifier(expr)) {
+                const symbol = getResolvedSymbol(expr);
+                const declaration = symbol.valueDeclaration;
+                if (declaration && (isBindingElement(declaration) || isParameter(declaration)) && reference === declaration.parent && !declaration.initializer && !declaration.dotDotDotToken) {
+                    return declaration;
+                }
+            }
+        }
+        else if (isAccessExpression(expr)) {
+            // An access expression is a candidate if the reference matches the left hand expression.
+            if (isMatchingReference(reference, expr.expression)) {
+                return expr;
+            }
+        }
+        else if (isIdentifier(expr)) {
+            const symbol = getResolvedSymbol(expr);
+            if (isConstantVariable(symbol)) {
+                const declaration = symbol.valueDeclaration!;
+                // Given 'const x = obj.kind', allow 'x' as an alias for 'obj.kind'
+                if (
+                    isVariableDeclaration(declaration) && !declaration.type && declaration.initializer && isAccessExpression(declaration.initializer) &&
+                    isMatchingReference(reference, declaration.initializer.expression)
+                ) {
+                    return declaration.initializer;
+                }
+                // Given 'const { kind: x } = obj', allow 'x' as an alias for 'obj.kind'
+                if (isBindingElement(declaration) && !declaration.initializer) {
+                    const parent = declaration.parent.parent;
+                    if (
+                        isVariableDeclaration(parent) && !parent.type && parent.initializer && (isIdentifier(parent.initializer) || isAccessExpression(parent.initializer)) &&
+                        isMatchingReference(reference, parent.initializer)
+                    ) {
+                        return declaration;
+                    }
+                }
+            }
+        }
+        return undefined;
+    }
+
     function getFlowNodeId(flow: FlowNode): number {
         if (!flow.id || flow.id < 0) {
             flow.id = nextFlowId;
@@ -28114,57 +28159,12 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             return result;
         }
 
-        function getCandidateDiscriminantPropertyAccess(expr: Expression) {
-            if (isBindingPattern(reference) || isFunctionExpressionOrArrowFunction(reference) || isObjectLiteralMethod(reference)) {
-                // When the reference is a binding pattern or function or arrow expression, we are narrowing a pesudo-reference in
-                // getNarrowedTypeOfSymbol. An identifier for a destructuring variable declared in the same binding pattern or
-                // parameter declared in the same parameter list is a candidate.
-                if (isIdentifier(expr)) {
-                    const symbol = getResolvedSymbol(expr);
-                    const declaration = symbol.valueDeclaration;
-                    if (declaration && (isBindingElement(declaration) || isParameter(declaration)) && reference === declaration.parent && !declaration.initializer && !declaration.dotDotDotToken) {
-                        return declaration;
-                    }
-                }
-            }
-            else if (isAccessExpression(expr)) {
-                // An access expression is a candidate if the reference matches the left hand expression.
-                if (isMatchingReference(reference, expr.expression)) {
-                    return expr;
-                }
-            }
-            else if (isIdentifier(expr)) {
-                const symbol = getResolvedSymbol(expr);
-                if (isConstantVariable(symbol)) {
-                    const declaration = symbol.valueDeclaration!;
-                    // Given 'const x = obj.kind', allow 'x' as an alias for 'obj.kind'
-                    if (
-                        isVariableDeclaration(declaration) && !declaration.type && declaration.initializer && isAccessExpression(declaration.initializer) &&
-                        isMatchingReference(reference, declaration.initializer.expression)
-                    ) {
-                        return declaration.initializer;
-                    }
-                    // Given 'const { kind: x } = obj', allow 'x' as an alias for 'obj.kind'
-                    if (isBindingElement(declaration) && !declaration.initializer) {
-                        const parent = declaration.parent.parent;
-                        if (
-                            isVariableDeclaration(parent) && !parent.type && parent.initializer && (isIdentifier(parent.initializer) || isAccessExpression(parent.initializer)) &&
-                            isMatchingReference(reference, parent.initializer)
-                        ) {
-                            return declaration;
-                        }
-                    }
-                }
-            }
-            return undefined;
-        }
-
         function getDiscriminantPropertyAccess(expr: Expression, computedType: Type) {
             // As long as the computed type is a subset of the declared type, we use the full declared type to detect
             // a discriminant property. In cases where the computed type isn't a subset, e.g because of a preceding type
             // predicate narrowing, we use the actual computed type.
             if (declaredType.flags & TypeFlags.Union || computedType.flags & TypeFlags.Union) {
-                const access = getCandidateDiscriminantPropertyAccess(expr);
+                const access = getCandidateDiscriminantPropertyAccess(expr, reference);
                 if (access) {
                     const name = getAccessedPropertyName(access);
                     if (name) {