Merge pull request #31802 from microsoft/wideningInAccessExpressions

Consistent widening in access expressions

src/compiler/checker.ts

@@ -20219,19 +20219,25 @@ namespace ts {
             return checkPropertyAccessExpressionOrQualifiedName(node, node.left, node.right);
         }
 
+        function isMethodAccessForCall(node: Node) {
+            while (node.parent.kind === SyntaxKind.ParenthesizedExpression) {
+                node = node.parent;
+            }
+            return isCallOrNewExpression(node.parent) && node.parent.expression === node;
+        }
+
         function checkPropertyAccessExpressionOrQualifiedName(node: PropertyAccessExpression | QualifiedName, left: Expression | QualifiedName, right: Identifier) {
             let propType: Type;
             const leftType = checkNonNullExpression(left);
             const parentSymbol = getNodeLinks(left).resolvedSymbol;
-            // We widen array literals to get type any[] instead of undefined[] in non-strict mode
-            const apparentType = getApparentType(isEmptyArrayLiteralType(leftType) ? getWidenedType(leftType) : leftType);
+            const assignmentKind = getAssignmentTargetKind(node);
+            const apparentType = getApparentType(assignmentKind !== AssignmentKind.None || isMethodAccessForCall(node) ? getWidenedType(leftType) : leftType);
             if (isTypeAny(apparentType) || apparentType === silentNeverType) {
                 if (isIdentifier(left) && parentSymbol) {
                     markAliasReferenced(parentSymbol, node);
                 }
                 return apparentType;
             }
-            const assignmentKind = getAssignmentTargetKind(node);
             const prop = getPropertyOfType(apparentType, right.escapedText);
             if (isIdentifier(left) && parentSymbol && !(prop && isConstEnumOrConstEnumOnlyModule(prop))) {
                 markAliasReferenced(parentSymbol, node);
@@ -20625,7 +20631,8 @@ namespace ts {
         }
 
         function checkIndexedAccess(node: ElementAccessExpression): Type {
-            const objectType = checkNonNullExpression(node.expression);
+            const exprType = checkNonNullExpression(node.expression);
+            const objectType = getAssignmentTargetKind(node) !== AssignmentKind.None || isMethodAccessForCall(node) ? getWidenedType(exprType) : exprType;
 
             const indexExpression = node.argumentExpression;
             if (!indexExpression) {

tests/baselines/reference/propertyAccessWidening.errors.txt

@@ -0,0 +1,34 @@
+tests/cases/conformance/expressions/propertyAccess/propertyAccessWidening.ts(18,21): error TS2339: Property 'a' does not exist on type '{ a: string; b: number; } | {}'.
+  Property 'a' does not exist on type '{}'.
+tests/cases/conformance/expressions/propertyAccess/propertyAccessWidening.ts(19,5): error TS7053: Element implicitly has an 'any' type because expression of type '"a"' can't be used to index type '{}'.
+  Property 'a' does not exist on type '{}'.
+
+
+==== tests/cases/conformance/expressions/propertyAccess/propertyAccessWidening.ts (2 errors) ====
+    // Repro from #31762
+    
+    function g1(headerNames: any) {
+        let t = [{ hasLineBreak: false, cells: [] }];
+        const table = [{cells: headerNames }].concat(t);
+    }
+    
+    function g2(headerNames: any) {
+        let t = [{ hasLineBreak: false, cells: [] }];
+        const table = [{cells: headerNames }]["concat"](t);
+    }
+    
+    // Object in property or element access is widened when target of assignment
+    
+    function foo(options?: { a: string, b: number }) {
+        let x1 = (options || {}).a;     // Object type not widened
+        let x2 = (options || {})["a"];  // Object type not widened
+        (options || {}).a = 1;          // Object type widened, error
+                        ~
+!!! error TS2339: Property 'a' does not exist on type '{ a: string; b: number; } | {}'.
+!!! error TS2339:   Property 'a' does not exist on type '{}'.
+        (options || {})["a"] = 1;       // Object type widened, error
+        ~~~~~~~~~~~~~~~~~~~~
+!!! error TS7053: Element implicitly has an 'any' type because expression of type '"a"' can't be used to index type '{}'.
+!!! error TS7053:   Property 'a' does not exist on type '{}'.
+    }
+    

tests/baselines/reference/propertyAccessWidening.js

@@ -0,0 +1,41 @@
+//// [propertyAccessWidening.ts]
+// Repro from #31762
+
+function g1(headerNames: any) {
+    let t = [{ hasLineBreak: false, cells: [] }];
+    const table = [{cells: headerNames }].concat(t);
+}
+
+function g2(headerNames: any) {
+    let t = [{ hasLineBreak: false, cells: [] }];
+    const table = [{cells: headerNames }]["concat"](t);
+}
+
+// Object in property or element access is widened when target of assignment
+
+function foo(options?: { a: string, b: number }) {
+    let x1 = (options || {}).a;     // Object type not widened
+    let x2 = (options || {})["a"];  // Object type not widened
+    (options || {}).a = 1;          // Object type widened, error
+    (options || {})["a"] = 1;       // Object type widened, error
+}
+
+
+//// [propertyAccessWidening.js]
+"use strict";
+// Repro from #31762
+function g1(headerNames) {
+    var t = [{ hasLineBreak: false, cells: [] }];
+    var table = [{ cells: headerNames }].concat(t);
+}
+function g2(headerNames) {
+    var t = [{ hasLineBreak: false, cells: [] }];
+    var table = [{ cells: headerNames }]["concat"](t);
+}
+// Object in property or element access is widened when target of assignment
+function foo(options) {
+    var x1 = (options || {}).a; // Object type not widened
+    var x2 = (options || {})["a"]; // Object type not widened
+    (options || {}).a = 1; // Object type widened, error
+    (options || {})["a"] = 1; // Object type widened, error
+}

tests/baselines/reference/propertyAccessWidening.symbols

@@ -0,0 +1,65 @@
+=== tests/cases/conformance/expressions/propertyAccess/propertyAccessWidening.ts ===
+// Repro from #31762
+
+function g1(headerNames: any) {
+>g1 : Symbol(g1, Decl(propertyAccessWidening.ts, 0, 0))
+>headerNames : Symbol(headerNames, Decl(propertyAccessWidening.ts, 2, 12))
+
+    let t = [{ hasLineBreak: false, cells: [] }];
+>t : Symbol(t, Decl(propertyAccessWidening.ts, 3, 7))
+>hasLineBreak : Symbol(hasLineBreak, Decl(propertyAccessWidening.ts, 3, 14))
+>cells : Symbol(cells, Decl(propertyAccessWidening.ts, 3, 35))
+
+    const table = [{cells: headerNames }].concat(t);
+>table : Symbol(table, Decl(propertyAccessWidening.ts, 4, 9))
+>[{cells: headerNames }].concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>cells : Symbol(cells, Decl(propertyAccessWidening.ts, 4, 20))
+>headerNames : Symbol(headerNames, Decl(propertyAccessWidening.ts, 2, 12))
+>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>t : Symbol(t, Decl(propertyAccessWidening.ts, 3, 7))
+}
+
+function g2(headerNames: any) {
+>g2 : Symbol(g2, Decl(propertyAccessWidening.ts, 5, 1))
+>headerNames : Symbol(headerNames, Decl(propertyAccessWidening.ts, 7, 12))
+
+    let t = [{ hasLineBreak: false, cells: [] }];
+>t : Symbol(t, Decl(propertyAccessWidening.ts, 8, 7))
+>hasLineBreak : Symbol(hasLineBreak, Decl(propertyAccessWidening.ts, 8, 14))
+>cells : Symbol(cells, Decl(propertyAccessWidening.ts, 8, 35))
+
+    const table = [{cells: headerNames }]["concat"](t);
+>table : Symbol(table, Decl(propertyAccessWidening.ts, 9, 9))
+>cells : Symbol(cells, Decl(propertyAccessWidening.ts, 9, 20))
+>headerNames : Symbol(headerNames, Decl(propertyAccessWidening.ts, 7, 12))
+>"concat" : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>t : Symbol(t, Decl(propertyAccessWidening.ts, 8, 7))
+}
+
+// Object in property or element access is widened when target of assignment
+
+function foo(options?: { a: string, b: number }) {
+>foo : Symbol(foo, Decl(propertyAccessWidening.ts, 10, 1))
+>options : Symbol(options, Decl(propertyAccessWidening.ts, 14, 13))
+>a : Symbol(a, Decl(propertyAccessWidening.ts, 14, 24))
+>b : Symbol(b, Decl(propertyAccessWidening.ts, 14, 35))
+
+    let x1 = (options || {}).a;     // Object type not widened
+>x1 : Symbol(x1, Decl(propertyAccessWidening.ts, 15, 7))
+>(options || {}).a : Symbol(a, Decl(propertyAccessWidening.ts, 14, 24))
+>options : Symbol(options, Decl(propertyAccessWidening.ts, 14, 13))
+>a : Symbol(a, Decl(propertyAccessWidening.ts, 14, 24))
+
+    let x2 = (options || {})["a"];  // Object type not widened
+>x2 : Symbol(x2, Decl(propertyAccessWidening.ts, 16, 7))
+>options : Symbol(options, Decl(propertyAccessWidening.ts, 14, 13))
+>"a" : Symbol(a, Decl(propertyAccessWidening.ts, 14, 24))
+
+    (options || {}).a = 1;          // Object type widened, error
+>options : Symbol(options, Decl(propertyAccessWidening.ts, 14, 13))
+
+    (options || {})["a"] = 1;       // Object type widened, error
+>options : Symbol(options, Decl(propertyAccessWidening.ts, 14, 13))
+>"a" : Symbol(a, Decl(propertyAccessWidening.ts, 14, 24))
+}
+

tests/baselines/reference/propertyAccessWidening.types

@@ -0,0 +1,100 @@
+=== tests/cases/conformance/expressions/propertyAccess/propertyAccessWidening.ts ===
+// Repro from #31762
+
+function g1(headerNames: any) {
+>g1 : (headerNames: any) => void
+>headerNames : any
+
+    let t = [{ hasLineBreak: false, cells: [] }];
+>t : { hasLineBreak: boolean; cells: never[]; }[]
+>[{ hasLineBreak: false, cells: [] }] : { hasLineBreak: boolean; cells: never[]; }[]
+>{ hasLineBreak: false, cells: [] } : { hasLineBreak: boolean; cells: never[]; }
+>hasLineBreak : boolean
+>false : false
+>cells : never[]
+>[] : never[]
+
+    const table = [{cells: headerNames }].concat(t);
+>table : { cells: any; }[]
+>[{cells: headerNames }].concat(t) : { cells: any; }[]
+>[{cells: headerNames }].concat : { (...items: ConcatArray<{ cells: any; }>[]): { cells: any; }[]; (...items: ({ cells: any; } | ConcatArray<{ cells: any; }>)[]): { cells: any; }[]; }
+>[{cells: headerNames }] : { cells: any; }[]
+>{cells: headerNames } : { cells: any; }
+>cells : any
+>headerNames : any
+>concat : { (...items: ConcatArray<{ cells: any; }>[]): { cells: any; }[]; (...items: ({ cells: any; } | ConcatArray<{ cells: any; }>)[]): { cells: any; }[]; }
+>t : { hasLineBreak: boolean; cells: never[]; }[]
+}
+
+function g2(headerNames: any) {
+>g2 : (headerNames: any) => void
+>headerNames : any
+
+    let t = [{ hasLineBreak: false, cells: [] }];
+>t : { hasLineBreak: boolean; cells: never[]; }[]
+>[{ hasLineBreak: false, cells: [] }] : { hasLineBreak: boolean; cells: never[]; }[]
+>{ hasLineBreak: false, cells: [] } : { hasLineBreak: boolean; cells: never[]; }
+>hasLineBreak : boolean
+>false : false
+>cells : never[]
+>[] : never[]
+
+    const table = [{cells: headerNames }]["concat"](t);
+>table : { cells: any; }[]
+>[{cells: headerNames }]["concat"](t) : { cells: any; }[]
+>[{cells: headerNames }]["concat"] : { (...items: ConcatArray<{ cells: any; }>[]): { cells: any; }[]; (...items: ({ cells: any; } | ConcatArray<{ cells: any; }>)[]): { cells: any; }[]; }
+>[{cells: headerNames }] : { cells: any; }[]
+>{cells: headerNames } : { cells: any; }
+>cells : any
+>headerNames : any
+>"concat" : "concat"
+>t : { hasLineBreak: boolean; cells: never[]; }[]
+}
+
+// Object in property or element access is widened when target of assignment
+
+function foo(options?: { a: string, b: number }) {
+>foo : (options?: { a: string; b: number; } | undefined) => void
+>options : { a: string; b: number; } | undefined
+>a : string
+>b : number
+
+    let x1 = (options || {}).a;     // Object type not widened
+>x1 : string | undefined
+>(options || {}).a : string | undefined
+>(options || {}) : { a: string; b: number; } | {}
+>options || {} : { a: string; b: number; } | {}
+>options : { a: string; b: number; } | undefined
+>{} : {}
+>a : string | undefined
+
+    let x2 = (options || {})["a"];  // Object type not widened
+>x2 : string | undefined
+>(options || {})["a"] : string | undefined
+>(options || {}) : { a: string; b: number; } | {}
+>options || {} : { a: string; b: number; } | {}
+>options : { a: string; b: number; } | undefined
+>{} : {}
+>"a" : "a"
+
+    (options || {}).a = 1;          // Object type widened, error
+>(options || {}).a = 1 : 1
+>(options || {}).a : any
+>(options || {}) : { a: string; b: number; } | {}
+>options || {} : { a: string; b: number; } | {}
+>options : { a: string; b: number; } | undefined
+>{} : {}
+>a : any
+>1 : 1
+
+    (options || {})["a"] = 1;       // Object type widened, error
+>(options || {})["a"] = 1 : 1
+>(options || {})["a"] : any
+>(options || {}) : { a: string; b: number; } | {}
+>options || {} : { a: string; b: number; } | {}
+>options : { a: string; b: number; } | undefined
+>{} : {}
+>"a" : "a"
+>1 : 1
+}
+

tests/cases/conformance/expressions/propertyAccess/propertyAccessWidening.ts

@@ -0,0 +1,22 @@
+// @strict: true
+
+// Repro from #31762
+
+function g1(headerNames: any) {
+    let t = [{ hasLineBreak: false, cells: [] }];
+    const table = [{cells: headerNames }].concat(t);
+}
+
+function g2(headerNames: any) {
+    let t = [{ hasLineBreak: false, cells: [] }];
+    const table = [{cells: headerNames }]["concat"](t);
+}
+
+// Object in property or element access is widened when target of assignment
+
+function foo(options?: { a: string, b: number }) {
+    let x1 = (options || {}).a;     // Object type not widened
+    let x2 = (options || {})["a"];  // Object type not widened
+    (options || {}).a = 1;          // Object type widened, error
+    (options || {})["a"] = 1;       // Object type widened, error
+}