Revert removal of nonInferrableAnyType

src/compiler/checker.ts

@@ -791,6 +791,7 @@ namespace ts {
         const wildcardType = createIntrinsicType(TypeFlags.Any, "any");
         const errorType = createIntrinsicType(TypeFlags.Any, "error");
         const unresolvedType = createIntrinsicType(TypeFlags.Any, "unresolved");
+        const nonInferrableAnyType = createIntrinsicType(TypeFlags.Any, "any", ObjectFlags.ContainsWideningType);
         const intrinsicMarkerType = createIntrinsicType(TypeFlags.Any, "intrinsic");
         const unknownType = createIntrinsicType(TypeFlags.Unknown, "unknown");
         const nonNullUnknownType = createIntrinsicType(TypeFlags.Unknown, "unknown");
@@ -9560,7 +9561,11 @@ namespace ts {
             if (reportErrors && !declarationBelongsToPrivateAmbientMember(element)) {
                 reportImplicitAny(element, anyType);
             }
-            return anyType;
+            // When we're including the pattern in the type (an indication we're obtaining a contextual type), we
+            // use a non-inferrable any type. Inference will never directly infer this type, but it is possible
+            // to infer a type that contains it, e.g. for a binding pattern like [foo] or { foo }. In such cases,
+            // widening of the binding pattern type substitutes a regular any for the non-inferrable any.
+            return includePatternInType ? nonInferrableAnyType : anyType;
         }
 
         // Return the type implied by an object binding pattern
@@ -22631,7 +22636,10 @@ namespace ts {
                         //
                         // This flag is infectious; if we produce Box<never> (where never is silentNeverType), Box<never> is
                         // also non-inferrable.
-                        if (getObjectFlags(source) & ObjectFlags.NonInferrableType) {
+                        //
+                        // As a special case, also ignore nonInferrableAnyType, which is a special form of the any type
+                        // used as a stand-in for binding elements when they are being inferred.
+                        if (getObjectFlags(source) & ObjectFlags.NonInferrableType || source === nonInferrableAnyType) {
                             return;
                         }
                         if (!inference.isFixed) {

tests/baselines/reference/issue50680.errors.txt

@@ -1,36 +0,0 @@
-tests/cases/compiler/issue50680.ts(5,11): error TS2322: Type 'string' is not assignable to type '"aa" | "bb"'.
-tests/cases/compiler/issue50680.ts(13,11): error TS2322: Type 'string' is not assignable to type '"aa" | "bb"'.
-tests/cases/compiler/issue50680.ts(14,11): error TS2322: Type 'string[]' is not assignable to type '("aa" | "bb")[]'.
-  Type 'string' is not assignable to type '"aa" | "bb"'.
-
-
-==== tests/cases/compiler/issue50680.ts (3 errors) ====
-    declare function func<T extends string>(arg: { keys: T[] }): { readonly keys: T[]; readonly firstKey: T; };
-    
-    function func1() {
-        const { firstKey } = func({keys: ["aa", "bb"]})
-        const a: "aa" | "bb" = firstKey;
-              ~
-!!! error TS2322: Type 'string' is not assignable to type '"aa" | "bb"'.
-    
-        const { keys } = func({keys: ["aa", "bb"]})
-        const b: ("aa" | "bb")[] = keys;
-    }
-      
-    function func2() {
-        const { keys, firstKey } = func({keys: ["aa", "bb"]})
-        const a: "aa" | "bb" = firstKey;
-              ~
-!!! error TS2322: Type 'string' is not assignable to type '"aa" | "bb"'.
-        const b: ("aa" | "bb")[] = keys;
-              ~
-!!! error TS2322: Type 'string[]' is not assignable to type '("aa" | "bb")[]'.
-!!! error TS2322:   Type 'string' is not assignable to type '"aa" | "bb"'.
-    }
-    
-    function func3() {
-        const x = func({keys: ["aa", "bb"]})
-        const a: "aa" | "bb" = x.firstKey;
-        const b: ("aa" | "bb")[] = x.keys;
-    }
-    

tests/baselines/reference/issue50680.types

@@ -10,18 +10,18 @@ function func1() {
 >func1 : () => void
 
     const { firstKey } = func({keys: ["aa", "bb"]})
->firstKey : string
->func({keys: ["aa", "bb"]}) : { readonly keys: string[]; readonly firstKey: string; }
+>firstKey : "aa" | "bb"
+>func({keys: ["aa", "bb"]}) : { readonly keys: ("aa" | "bb")[]; readonly firstKey: "aa" | "bb"; }
 >func : <T extends string>(arg: { keys: T[]; }) => { readonly keys: T[]; readonly firstKey: T; }
->{keys: ["aa", "bb"]} : { keys: string[]; }
->keys : string[]
->["aa", "bb"] : string[]
+>{keys: ["aa", "bb"]} : { keys: ("aa" | "bb")[]; }
+>keys : ("aa" | "bb")[]
+>["aa", "bb"] : ("aa" | "bb")[]
 >"aa" : "aa"
 >"bb" : "bb"
 
     const a: "aa" | "bb" = firstKey;
 >a : "aa" | "bb"
->firstKey : string
+>firstKey : "aa" | "bb"
 
     const { keys } = func({keys: ["aa", "bb"]})
 >keys : ("aa" | "bb")[]
@@ -42,23 +42,23 @@ function func2() {
 >func2 : () => void
 
     const { keys, firstKey } = func({keys: ["aa", "bb"]})
->keys : string[]
->firstKey : string
->func({keys: ["aa", "bb"]}) : { readonly keys: string[]; readonly firstKey: string; }
+>keys : ("aa" | "bb")[]
+>firstKey : "aa" | "bb"
+>func({keys: ["aa", "bb"]}) : { readonly keys: ("aa" | "bb")[]; readonly firstKey: "aa" | "bb"; }
 >func : <T extends string>(arg: { keys: T[]; }) => { readonly keys: T[]; readonly firstKey: T; }
->{keys: ["aa", "bb"]} : { keys: string[]; }
->keys : string[]
->["aa", "bb"] : string[]
+>{keys: ["aa", "bb"]} : { keys: ("aa" | "bb")[]; }
+>keys : ("aa" | "bb")[]
+>["aa", "bb"] : ("aa" | "bb")[]
 >"aa" : "aa"
 >"bb" : "bb"
 
     const a: "aa" | "bb" = firstKey;
 >a : "aa" | "bb"
->firstKey : string
+>firstKey : "aa" | "bb"
 
     const b: ("aa" | "bb")[] = keys;
 >b : ("aa" | "bb")[]
->keys : string[]
+>keys : ("aa" | "bb")[]
 }
 
 function func3() {