Do not report errors during contextual typecheck

Fixes #8229

src/compiler/checker.ts

@@ -2873,7 +2873,7 @@ namespace ts {
 
             // If the declaration specifies a binding pattern, use the type implied by the binding pattern
             if (isBindingPattern(declaration.name)) {
-                return getTypeFromBindingPattern(<BindingPattern>declaration.name, /*includePatternInType*/ false);
+                return getTypeFromBindingPattern(<BindingPattern>declaration.name, /*includePatternInType*/ false, /*reportErrors*/ true);
             }
 
             // No type specified and nothing can be inferred
@@ -2883,23 +2883,25 @@ namespace ts {
         // Return the type implied by a binding pattern element. This is the type of the initializer of the element if
         // one is present. Otherwise, if the element is itself a binding pattern, it is the type implied by the binding
         // pattern. Otherwise, it is the type any.
-        function getTypeFromBindingElement(element: BindingElement, includePatternInType?: boolean): Type {
+        function getTypeFromBindingElement(element: BindingElement, includePatternInType?: boolean, reportErrors?: boolean): Type {
             if (element.initializer) {
                 const type = checkExpressionCached(element.initializer);
-                reportErrorsFromWidening(element, type);
+                if (reportErrors) {
+                    reportErrorsFromWidening(element, type);
+                }
                 return getWidenedType(type);
             }
             if (isBindingPattern(element.name)) {
-                return getTypeFromBindingPattern(<BindingPattern>element.name, includePatternInType);
+                return getTypeFromBindingPattern(<BindingPattern>element.name, includePatternInType, reportErrors);
             }
-            if (compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
+            if (reportErrors && compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
                 reportImplicitAnyError(element, anyType);
             }
             return anyType;
         }
 
         // Return the type implied by an object binding pattern
-        function getTypeFromObjectBindingPattern(pattern: BindingPattern, includePatternInType: boolean): Type {
+        function getTypeFromObjectBindingPattern(pattern: BindingPattern, includePatternInType: boolean, reportErrors: boolean): Type {
             const members: SymbolTable = {};
             let hasComputedProperties = false;
             forEach(pattern.elements, e => {
@@ -2913,7 +2915,7 @@ namespace ts {
                 const text = getTextOfPropertyName(name);
                 const flags = SymbolFlags.Property | SymbolFlags.Transient | (e.initializer ? SymbolFlags.Optional : 0);
                 const symbol = <TransientSymbol>createSymbol(flags, text);
-                symbol.type = getTypeFromBindingElement(e, includePatternInType);
+                symbol.type = getTypeFromBindingElement(e, includePatternInType, reportErrors);
                 symbol.bindingElement = e;
                 members[symbol.name] = symbol;
             });
@@ -2928,13 +2930,13 @@ namespace ts {
         }
 
         // Return the type implied by an array binding pattern
-        function getTypeFromArrayBindingPattern(pattern: BindingPattern, includePatternInType: boolean): Type {
+        function getTypeFromArrayBindingPattern(pattern: BindingPattern, includePatternInType: boolean, reportErrors: boolean): Type {
             const elements = pattern.elements;
             if (elements.length === 0 || elements[elements.length - 1].dotDotDotToken) {
                 return languageVersion >= ScriptTarget.ES6 ? createIterableType(anyType) : anyArrayType;
             }
             // If the pattern has at least one element, and no rest element, then it should imply a tuple type.
-            const elementTypes = map(elements, e => e.kind === SyntaxKind.OmittedExpression ? anyType : getTypeFromBindingElement(e, includePatternInType));
+            const elementTypes = map(elements, e => e.kind === SyntaxKind.OmittedExpression ? anyType : getTypeFromBindingElement(e, includePatternInType, reportErrors));
             if (includePatternInType) {
                 const result = createNewTupleType(elementTypes);
                 result.pattern = pattern;
@@ -2950,10 +2952,10 @@ namespace ts {
         // used as the contextual type of an initializer associated with the binding pattern. Also, for a destructuring
         // parameter with no type annotation or initializer, the type implied by the binding pattern becomes the type of
         // the parameter.
-        function getTypeFromBindingPattern(pattern: BindingPattern, includePatternInType?: boolean): Type {
+        function getTypeFromBindingPattern(pattern: BindingPattern, includePatternInType?: boolean, reportErrors?: boolean): Type {
             return pattern.kind === SyntaxKind.ObjectBindingPattern
-                ? getTypeFromObjectBindingPattern(pattern, includePatternInType)
-                : getTypeFromArrayBindingPattern(pattern, includePatternInType);
+                ? getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors)
+                : getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors);
         }
 
         // Return the type associated with a variable, parameter, or property declaration. In the simple case this is the type
@@ -8467,7 +8469,7 @@ namespace ts {
                     }
                 }
                 if (isBindingPattern(declaration.name)) {
-                    return getTypeFromBindingPattern(<BindingPattern>declaration.name, /*includePatternInType*/ true);
+                    return getTypeFromBindingPattern(<BindingPattern>declaration.name, /*includePatternInType*/ true, /*reportErrors*/ false);
                 }
                 if (isBindingPattern(declaration.parent)) {
                     const parentDeclaration = declaration.parent.parent;

tests/baselines/reference/noImplicitAnyDestructuringVarDeclaration2.symbols

@@ -0,0 +1,78 @@
+=== tests/cases/compiler/noImplicitAnyDestructuringVarDeclaration2.ts ===
+let [a, b, c] = [1, 2, 3]; // no error
+>a : Symbol(a, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 0, 5))
+>b : Symbol(b, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 0, 7))
+>c : Symbol(c, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 0, 10))
+
+let [a1 = 10, b1 = 10, c1 = 10] = [1, 2, 3]; // no error
+>a1 : Symbol(a1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 1, 5))
+>b1 : Symbol(b1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 1, 13))
+>c1 : Symbol(c1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 1, 22))
+
+let [a2 = undefined, b2 = undefined, c2 = undefined] = [1, 2, 3]; // no error
+>a2 : Symbol(a2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 2, 5))
+>undefined : Symbol(undefined)
+>b2 : Symbol(b2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 2, 20))
+>undefined : Symbol(undefined)
+>c2 : Symbol(c2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 2, 36))
+>undefined : Symbol(undefined)
+
+let [a3 = <any>undefined, b3 = <any>null, c3 = <any>undefined] = [1, 2, 3]; // no error
+>a3 : Symbol(a3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 3, 5))
+>undefined : Symbol(undefined)
+>b3 : Symbol(b3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 3, 25))
+>c3 : Symbol(c3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 3, 41))
+>undefined : Symbol(undefined)
+
+let [a4] = [<any>undefined], [b4] = [<any>null], c4 = <any>undefined, d4 = <any>null; // no error
+>a4 : Symbol(a4, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 4, 5))
+>undefined : Symbol(undefined)
+>b4 : Symbol(b4, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 4, 30))
+>c4 : Symbol(c4, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 4, 48))
+>undefined : Symbol(undefined)
+>d4 : Symbol(d4, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 4, 69))
+
+let {x, y, z} = { x: 1, y: 2, z: 3 }; // no error
+>x : Symbol(x, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 6, 5))
+>y : Symbol(y, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 6, 7))
+>z : Symbol(z, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 6, 10))
+>x : Symbol(x, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 6, 17))
+>y : Symbol(y, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 6, 23))
+>z : Symbol(z, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 6, 29))
+
+let {x1 = 10, y1 = 10, z1 = 10} = { x1: 1, y1: 2, z1: 3 }; // no error
+>x1 : Symbol(x1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 7, 5))
+>y1 : Symbol(y1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 7, 13))
+>z1 : Symbol(z1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 7, 22))
+>x1 : Symbol(x1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 7, 35))
+>y1 : Symbol(y1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 7, 42))
+>z1 : Symbol(z1, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 7, 49))
+
+let {x2 = undefined, y2 = undefined, z2 = undefined} = { x2: 1, y2: 2, z2: 3 }; // no error
+>x2 : Symbol(x2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 8, 5))
+>undefined : Symbol(undefined)
+>y2 : Symbol(y2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 8, 20))
+>undefined : Symbol(undefined)
+>z2 : Symbol(z2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 8, 36))
+>undefined : Symbol(undefined)
+>x2 : Symbol(x2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 8, 56))
+>y2 : Symbol(y2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 8, 63))
+>z2 : Symbol(z2, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 8, 70))
+
+let {x3 = <any>undefined, y3 = <any>null, z3 = <any>undefined} = { x3: 1, y3: 2, z3: 3 }; // no error
+>x3 : Symbol(x3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 9, 5))
+>undefined : Symbol(undefined)
+>y3 : Symbol(y3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 9, 25))
+>z3 : Symbol(z3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 9, 41))
+>undefined : Symbol(undefined)
+>x3 : Symbol(x3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 9, 66))
+>y3 : Symbol(y3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 9, 73))
+>z3 : Symbol(z3, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 9, 80))
+
+let {x4} = { x4: <any>undefined }, {y4} = { y4: <any>null }; // no error
+>x4 : Symbol(x4, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 10, 5))
+>x4 : Symbol(x4, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 10, 12))
+>undefined : Symbol(undefined)
+>y4 : Symbol(y4, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 10, 36))
+>y4 : Symbol(y4, Decl(noImplicitAnyDestructuringVarDeclaration2.ts, 10, 43))
+

tests/baselines/reference/noImplicitAnyDestructuringVarDeclaration2.types

@@ -0,0 +1,137 @@
+=== tests/cases/compiler/noImplicitAnyDestructuringVarDeclaration2.ts ===
+let [a, b, c] = [1, 2, 3]; // no error
+>a : number
+>b : number
+>c : number
+>[1, 2, 3] : [number, number, number]
+>1 : number
+>2 : number
+>3 : number
+
+let [a1 = 10, b1 = 10, c1 = 10] = [1, 2, 3]; // no error
+>a1 : number
+>10 : number
+>b1 : number
+>10 : number
+>c1 : number
+>10 : number
+>[1, 2, 3] : [number, number, number]
+>1 : number
+>2 : number
+>3 : number
+
+let [a2 = undefined, b2 = undefined, c2 = undefined] = [1, 2, 3]; // no error
+>a2 : number
+>undefined : undefined
+>b2 : number
+>undefined : undefined
+>c2 : number
+>undefined : undefined
+>[1, 2, 3] : [number, number, number]
+>1 : number
+>2 : number
+>3 : number
+
+let [a3 = <any>undefined, b3 = <any>null, c3 = <any>undefined] = [1, 2, 3]; // no error
+>a3 : number
+><any>undefined : any
+>undefined : undefined
+>b3 : number
+><any>null : any
+>null : null
+>c3 : number
+><any>undefined : any
+>undefined : undefined
+>[1, 2, 3] : [number, number, number]
+>1 : number
+>2 : number
+>3 : number
+
+let [a4] = [<any>undefined], [b4] = [<any>null], c4 = <any>undefined, d4 = <any>null; // no error
+>a4 : any
+>[<any>undefined] : [any]
+><any>undefined : any
+>undefined : undefined
+>b4 : any
+>[<any>null] : [any]
+><any>null : any
+>null : null
+>c4 : any
+><any>undefined : any
+>undefined : undefined
+>d4 : any
+><any>null : any
+>null : null
+
+let {x, y, z} = { x: 1, y: 2, z: 3 }; // no error
+>x : number
+>y : number
+>z : number
+>{ x: 1, y: 2, z: 3 } : { x: number; y: number; z: number; }
+>x : number
+>1 : number
+>y : number
+>2 : number
+>z : number
+>3 : number
+
+let {x1 = 10, y1 = 10, z1 = 10} = { x1: 1, y1: 2, z1: 3 }; // no error
+>x1 : number
+>10 : number
+>y1 : number
+>10 : number
+>z1 : number
+>10 : number
+>{ x1: 1, y1: 2, z1: 3 } : { x1?: number; y1?: number; z1?: number; }
+>x1 : number
+>1 : number
+>y1 : number
+>2 : number
+>z1 : number
+>3 : number
+
+let {x2 = undefined, y2 = undefined, z2 = undefined} = { x2: 1, y2: 2, z2: 3 }; // no error
+>x2 : number
+>undefined : undefined
+>y2 : number
+>undefined : undefined
+>z2 : number
+>undefined : undefined
+>{ x2: 1, y2: 2, z2: 3 } : { x2?: number; y2?: number; z2?: number; }
+>x2 : number
+>1 : number
+>y2 : number
+>2 : number
+>z2 : number
+>3 : number
+
+let {x3 = <any>undefined, y3 = <any>null, z3 = <any>undefined} = { x3: 1, y3: 2, z3: 3 }; // no error
+>x3 : number
+><any>undefined : any
+>undefined : undefined
+>y3 : number
+><any>null : any
+>null : null
+>z3 : number
+><any>undefined : any
+>undefined : undefined
+>{ x3: 1, y3: 2, z3: 3 } : { x3?: number; y3?: number; z3?: number; }
+>x3 : number
+>1 : number
+>y3 : number
+>2 : number
+>z3 : number
+>3 : number
+
+let {x4} = { x4: <any>undefined }, {y4} = { y4: <any>null }; // no error
+>x4 : any
+>{ x4: <any>undefined } : { x4: any; }
+>x4 : any
+><any>undefined : any
+>undefined : undefined
+>y4 : any
+>{ y4: <any>null } : { y4: any; }
+>y4 : any
+><any>null : any
+>null : null
+