Assume outer variables are always initialized in control flow analysis

Author: ahejlsberg

src/compiler/checker.ts

@@ -8920,6 +8920,7 @@ namespace ts {
             const isParameter = getRootDeclaration(declaration).kind === SyntaxKind.Parameter;
             const declarationContainer = getControlFlowContainer(declaration);
             let flowContainer = getControlFlowContainer(node);
+            const isOuterVariable = flowContainer !== declarationContainer;
             // When the control flow originates in a function expression or arrow function and we are referencing
             // a const variable or parameter from an outer function, we extend the origin of the control flow
             // analysis to include the immediately enclosing function.
@@ -8932,7 +8933,7 @@ namespace ts {
             // the entire control flow graph from the variable's declaration (i.e. when the flow container and
             // declaration container are the same).
             const assumeInitialized = !strictNullChecks || (type.flags & TypeFlags.Any) !== 0 || isParameter ||
-                flowContainer !== declarationContainer || isInAmbientContext(declaration);
+                isOuterVariable || isInAmbientContext(declaration);
             const flowType = getFlowTypeOfReference(node, type, assumeInitialized, flowContainer);
             // A variable is considered uninitialized when it is possible to analyze the entire control flow graph
             // from declaration to use, and when the variable's declared type doesn't include undefined but the