Use intersection strategy

Author: Andarist

src/compiler/checker.ts

@@ -31929,16 +31929,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         // return type of 'wrap'.
         if (node.kind !== SyntaxKind.Decorator) {
             const skipBindingPatterns = every(signature.typeParameters, p => !!getDefaultFromTypeParameter(p));
-            const contextualType = getContextualType(node, skipBindingPatterns ? ContextFlags.SkipBindingPatterns : ContextFlags.None);
+            let contextualType = getContextualType(node, skipBindingPatterns ? ContextFlags.SkipBindingPatterns : ContextFlags.None);
             if (contextualType) {
                 const inferenceTargetType = getReturnTypeOfSignature(signature);
-                const targetConstraint = getConstraintOfType(inferenceTargetType);
-                const applicableContextualType = targetConstraint && !isTypeAssignableTo(targetConstraint, contextualType) ?
-                    filterType(contextualType, t => isTypeAssignableTo(t, targetConstraint)) :
-                    contextualType;
                 if (couldContainTypeVariables(inferenceTargetType)) {
+                    const targetConstraint = getConstraintOfType(inferenceTargetType);
+                    contextualType = targetConstraint ? getIntersectionType([contextualType, targetConstraint]) : contextualType;
                     const outerContext = getInferenceContext(node);
-                    const isFromBindingPattern = !skipBindingPatterns && getContextualType(node, ContextFlags.SkipBindingPatterns) !== applicableContextualType;
+                    const isFromBindingPattern = !skipBindingPatterns && getContextualType(node, ContextFlags.SkipBindingPatterns) !== contextualType;
                     // A return type inference from a binding pattern can be used in instantiating the contextual
                     // type of an argument later in inference, but cannot stand on its own as the final return type.
                     // It is incorporated into `context.returnMapper` which is used in `instantiateContextualType`,
@@ -31954,7 +31952,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                         // outer call expression. Effectively we just want a snapshot of whatever has been
                         // inferred for any outer call expression so far.
                         const outerMapper = getMapperFromContext(cloneInferenceContext(outerContext, InferenceFlags.NoDefault));
-                        const instantiatedType = instantiateType(applicableContextualType, outerMapper);
+                        const instantiatedType = instantiateType(contextualType, outerMapper);
                         // If the contextual type is a generic function type with a single call signature, we
                         // instantiate the type with its own type parameters and type arguments. This ensures that
                         // the type parameters are not erased to type any during type inference such that they can
@@ -31974,7 +31972,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     // the source type uses the outer context's return mapper (which excludes inferences made from
                     // outer arguments), and (b) we don't want any further inferences going into this context.
                     const returnContext = createInferenceContext(signature.typeParameters!, signature, context.flags);
-                    const returnSourceType = instantiateType(applicableContextualType, outerContext && outerContext.returnMapper);
+                    const returnSourceType = instantiateType(contextualType, outerContext && outerContext.returnMapper);
                     inferTypes(returnContext.inferences, returnSourceType, inferenceTargetType);
                     context.returnMapper = some(returnContext.inferences, hasInferenceCandidates) ? getMapperFromContext(cloneInferredPartOfContext(returnContext)) : undefined;
                 }

src/compiler/sys.ts

@@ -1602,7 +1602,8 @@ export let sys: System = (() => {
             disableCPUProfiler,
             cpuProfilingEnabled: () => !!activeSession || contains(process.execArgv, "--cpu-prof") || contains(process.execArgv, "--prof"),
             realpath,
-            debugMode: !!process.env.NODE_INSPECTOR_IPC || !!process.env.VSCODE_INSPECTOR_OPTIONS || some(process.execArgv as string[], arg => /^--(inspect|debug)(-brk)?(=\d+)?$/i.test(arg)),
+            // debugMode: !!process.env.NODE_INSPECTOR_IPC || !!process.env.VSCODE_INSPECTOR_OPTIONS || some(process.execArgv as string[], arg => /^--(inspect|debug)(-brk)?(=\d+)?$/i.test(arg)),
+            debugMode: true,
             tryEnableSourceMapsForHost() {
                 try {
                     (require("source-map-support") as typeof import("source-map-support")).install();

tests/baselines/reference/deepComparisons.types

@@ -83,7 +83,7 @@ function g() {
 
     return f() as F<any>;
 >f() as F<any> : F<any>
->f() : F<any>
+>f() : F<T>
 >f : <T = any>() => F<T>
 }
 

tests/baselines/reference/nonnullAssertionPropegatesContextualType.types

@@ -1,8 +1,8 @@
 === tests/cases/compiler/nonnullAssertionPropegatesContextualType.ts ===
 let rect2: SVGRectElement = document.querySelector('.svg-rectangle')!; // Error: Element
 >rect2 : SVGRectElement
->document.querySelector('.svg-rectangle')! : SVGRectElement
->document.querySelector('.svg-rectangle') : SVGRectElement | null
+>document.querySelector('.svg-rectangle')! : SVGRectElement & Element
+>document.querySelector('.svg-rectangle') : (SVGRectElement & Element) | null
 >document.querySelector : { <K extends keyof HTMLElementTagNameMap>(selectors: K): HTMLElementTagNameMap[K] | null; <K extends keyof SVGElementTagNameMap>(selectors: K): SVGElementTagNameMap[K] | null; <K extends keyof MathMLElementTagNameMap>(selectors: K): MathMLElementTagNameMap[K] | null; <K extends keyof HTMLElementDeprecatedTagNameMap>(selectors: K): HTMLElementDeprecatedTagNameMap[K] | null; <E extends Element = Element>(selectors: string): E | null; }
 >document : Document
 >querySelector : { <K extends keyof HTMLElementTagNameMap>(selectors: K): HTMLElementTagNameMap[K] | null; <K extends keyof SVGElementTagNameMap>(selectors: K): SVGElementTagNameMap[K] | null; <K extends keyof MathMLElementTagNameMap>(selectors: K): MathMLElementTagNameMap[K] | null; <K extends keyof HTMLElementDeprecatedTagNameMap>(selectors: K): HTMLElementDeprecatedTagNameMap[K] | null; <E extends Element = Element>(selectors: string): E | null; }