Stop looking at binding patterns for type argument inference

src/compiler/checker.ts

@@ -25274,7 +25274,8 @@ namespace ts {
                 if (result) {
                     return result;
                 }
-                if (!(contextFlags! & ContextFlags.SkipBindingPatterns) && isBindingPattern(declaration.name)) { // This is less a contextual type and more an implied shape - in some cases, this may be undesirable
+                if (!(contextFlags! & ContextFlags.SkipBindingPatterns) && isBindingPattern(declaration.name)) {
+                    // This is less a contextual type and more an implied shape - in some cases, this may be undesirable
                     return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ true, /*reportErrors*/ false);
                 }
             }
@@ -28573,7 +28574,7 @@ namespace ts {
             // 'let f: (x: string) => number = wrap(s => s.length)', we infer from the declared type of 'f' to the
             // return type of 'wrap'.
             if (node.kind !== SyntaxKind.Decorator) {
-                const contextualType = getContextualType(node, every(signature.typeParameters, p => !!getDefaultFromTypeParameter(p)) ? ContextFlags.SkipBindingPatterns : ContextFlags.None);
+                const contextualType = getContextualType(node, ContextFlags.SkipBindingPatterns);
                 if (contextualType) {
                     // We clone the inference context to avoid disturbing a resolution in progress for an
                     // outer call expression. Effectively we just want a snapshot of whatever has been

tests/baselines/reference/destructuringTuple.errors.txt

@@ -1,18 +1,11 @@
-tests/cases/compiler/destructuringTuple.ts(11,7): error TS2461: Type 'number' is not an array type.
-tests/cases/compiler/destructuringTuple.ts(11,48): error TS2769: No overload matches this call.
-  Overload 1 of 3, '(callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number', gave the following error.
-    Type 'never[]' is not assignable to type 'number'.
-  Overload 2 of 3, '(callbackfn: (previousValue: [], currentValue: number, currentIndex: number, array: number[]) => [], initialValue: []): []', gave the following error.
-    Type 'never[]' is not assignable to type '[]'.
-      Target allows only 0 element(s) but source may have more.
 tests/cases/compiler/destructuringTuple.ts(11,60): error TS2769: No overload matches this call.
   Overload 1 of 2, '(...items: ConcatArray<never>[]): never[]', gave the following error.
     Argument of type 'number' is not assignable to parameter of type 'ConcatArray<never>'.
   Overload 2 of 2, '(...items: ConcatArray<never>[]): never[]', gave the following error.
     Argument of type 'number' is not assignable to parameter of type 'ConcatArray<never>'.
 
 
-==== tests/cases/compiler/destructuringTuple.ts (3 errors) ====
+==== tests/cases/compiler/destructuringTuple.ts (1 errors) ====
     declare var tuple: [boolean, number, ...string[]];
 
     const [a, b, c, ...rest] = tuple;
@@ -24,17 +17,6 @@ tests/cases/compiler/destructuringTuple.ts(11,60): error TS2769: No overload mat
     // Repros from #32140
 
     const [oops1] = [1, 2, 3].reduce((accu, el) => accu.concat(el), []);
-          ~~~~~~~
-!!! error TS2461: Type 'number' is not an array type.
-                                                   ~~~~~~~~~~~~~~~
-!!! error TS2769: No overload matches this call.
-!!! error TS2769:   Overload 1 of 3, '(callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number', gave the following error.
-!!! error TS2769:     Type 'never[]' is not assignable to type 'number'.
-!!! error TS2769:   Overload 2 of 3, '(callbackfn: (previousValue: [], currentValue: number, currentIndex: number, array: number[]) => [], initialValue: []): []', gave the following error.
-!!! error TS2769:     Type 'never[]' is not assignable to type '[]'.
-!!! error TS2769:       Target allows only 0 element(s) but source may have more.
-!!! related TS6502 /.ts/lib.es5.d.ts:1412:24: The expected type comes from the return type of this signature.
-!!! related TS6502 /.ts/lib.es5.d.ts:1418:27: The expected type comes from the return type of this signature.
                                                                ~~
 !!! error TS2769: No overload matches this call.
 !!! error TS2769:   Overload 1 of 2, '(...items: ConcatArray<never>[]): never[]', gave the following error.

tests/baselines/reference/destructuringTuple.types

@@ -23,20 +23,20 @@ declare var receiver: typeof tuple;
 // Repros from #32140
 
 const [oops1] = [1, 2, 3].reduce((accu, el) => accu.concat(el), []);
->oops1 : any
->[1, 2, 3].reduce((accu, el) => accu.concat(el), []) : number
+>oops1 : never
+>[1, 2, 3].reduce((accu, el) => accu.concat(el), []) : never[]
 >[1, 2, 3].reduce : { (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number): number; (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number; <U>(callbackfn: (previousValue: U, currentValue: number, currentIndex: number, array: number[]) => U, initialValue: U): U; }
 >[1, 2, 3] : number[]
 >1 : 1
 >2 : 2
 >3 : 3
 >reduce : { (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number): number; (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number; <U>(callbackfn: (previousValue: U, currentValue: number, currentIndex: number, array: number[]) => U, initialValue: U): U; }
->(accu, el) => accu.concat(el) : (accu: [], el: number) => never[]
->accu : []
+>(accu, el) => accu.concat(el) : (accu: never[], el: number) => never[]
+>accu : never[]
 >el : number
 >accu.concat(el) : never[]
 >accu.concat : { (...items: ConcatArray<never>[]): never[]; (...items: ConcatArray<never>[]): never[]; }
->accu : []
+>accu : never[]
 >concat : { (...items: ConcatArray<never>[]): never[]; (...items: ConcatArray<never>[]): never[]; }
 >el : number
 >[] : never[]

tests/cases/fourslash/completionsBindingPatternAffectsInference.ts

@@ -0,0 +1,9 @@
+/// <reference path="fourslash.ts" />
+
+//// declare function pick<T, K extends keyof T>(keys: K[], obj: T): Pick<T, K>;
+//// const { /**/ } = pick(['b'], { a: 'a', b: 'b' });
+
+verify.completions({
+  marker: "",
+  exact: ["b"]
+});