fix(50340): typeof ... === "undefined" check on discriminated union o…

…f undefined and object type doesn't narrow correctly (#50344) * fix(50340): narrow type by discriminant in typeof * add additional test cases
microsoft · Aug 31, 2022 · a9797d2 · a9797d2
1 parent 43f8ae6
commit a9797d2
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diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -25328,11 +25328,19 @@ namespace ts {
                 }
                 const target = getReferenceCandidate(typeOfExpr.expression);
                 if (!isMatchingReference(reference, target)) {
+                    const propertyAccess = getDiscriminantPropertyAccess(typeOfExpr.expression, type);
+                    if (propertyAccess) {
+                        return narrowTypeByDiscriminant(type, propertyAccess, t => narrowTypeByLiteralExpression(t, literal, assumeTrue));
+                    }
                     if (strictNullChecks && optionalChainContainsReference(target, reference) && assumeTrue === (literal.text !== "undefined")) {
                         return getAdjustedTypeWithFacts(type, TypeFacts.NEUndefinedOrNull);
                     }
                     return type;
                 }
+                return narrowTypeByLiteralExpression(type, literal, assumeTrue);
+            }
+
+            function narrowTypeByLiteralExpression(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
                 return assumeTrue ?
                     narrowTypeByTypeName(type, literal.text) :
                     getTypeWithFacts(type, typeofNEFacts.get(literal.text) || TypeFacts.TypeofNEHostObject);

diff --git a/tests/baselines/reference/narrowingTypeofUndefined.js b/tests/baselines/reference/narrowingTypeofUndefined.js
@@ -0,0 +1,31 @@
+//// [narrowingTypeofUndefined.ts]
+declare const a: { error: { prop: string }, result: undefined } | { error: undefined, result: { prop: number } }
+
+if (typeof a.error === 'undefined') {
+    a.result.prop; // number
+}
+else {
+    a.error.prop; // string
+}
+
+if (typeof a.error !== 'undefined') {
+    a.error.prop; // string
+}
+else {
+    a.result.prop; // number
+}
+
+
+//// [narrowingTypeofUndefined.js]
+if (typeof a.error === 'undefined') {
+    a.result.prop; // number
+}
+else {
+    a.error.prop; // string
+}
+if (typeof a.error !== 'undefined') {
+    a.error.prop; // string
+}
+else {
+    a.result.prop; // number
+}
diff --git a/tests/baselines/reference/narrowingTypeofUndefined.symbols b/tests/baselines/reference/narrowingTypeofUndefined.symbols
@@ -0,0 +1,52 @@
+=== tests/cases/compiler/narrowingTypeofUndefined.ts ===
+declare const a: { error: { prop: string }, result: undefined } | { error: undefined, result: { prop: number } }
+>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
+>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18))
+>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
+>result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43))
+>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 67))
+>result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 85))
+>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
+
+if (typeof a.error === 'undefined') {
+>a.error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
+>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
+>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
+
+    a.result.prop; // number
+>a.result.prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
+>a.result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43), Decl(narrowingTypeofUndefined.ts, 0, 85))
+>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
+>result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43), Decl(narrowingTypeofUndefined.ts, 0, 85))
+>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
+}
+else {
+    a.error.prop; // string
+>a.error.prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
+>a.error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
+>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
+>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
+>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
+}
+
+if (typeof a.error !== 'undefined') {
+>a.error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
+>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
+>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
+
+    a.error.prop; // string
+>a.error.prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
+>a.error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
+>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
+>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
+>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
+}
+else {
+    a.result.prop; // number
+>a.result.prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
+>a.result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43), Decl(narrowingTypeofUndefined.ts, 0, 85))
+>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
+>result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43), Decl(narrowingTypeofUndefined.ts, 0, 85))
+>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
+}
+
diff --git a/tests/baselines/reference/narrowingTypeofUndefined.types b/tests/baselines/reference/narrowingTypeofUndefined.types
@@ -0,0 +1,58 @@
+=== tests/cases/compiler/narrowingTypeofUndefined.ts ===
+declare const a: { error: { prop: string }, result: undefined } | { error: undefined, result: { prop: number } }
+>a : { error: {    prop: string;}; result: undefined; } | { error: undefined; result: {    prop: number;}; }
+>error : { prop: string; }
+>prop : string
+>result : undefined
+>error : undefined
+>result : { prop: number; }
+>prop : number
+
+if (typeof a.error === 'undefined') {
+>typeof a.error === 'undefined' : boolean
+>typeof a.error : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>a.error : { prop: string; }
+>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
+>error : { prop: string; }
+>'undefined' : "undefined"
+
+    a.result.prop; // number
+>a.result.prop : number
+>a.result : { prop: number; }
+>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
+>result : { prop: number; }
+>prop : number
+}
+else {
+    a.error.prop; // string
+>a.error.prop : string
+>a.error : { prop: string; }
+>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
+>error : { prop: string; }
+>prop : string
+}
+
+if (typeof a.error !== 'undefined') {
+>typeof a.error !== 'undefined' : boolean
+>typeof a.error : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>a.error : { prop: string; }
+>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
+>error : { prop: string; }
+>'undefined' : "undefined"
+
+    a.error.prop; // string
+>a.error.prop : string
+>a.error : { prop: string; }
+>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
+>error : { prop: string; }
+>prop : string
+}
+else {
+    a.result.prop; // number
+>a.result.prop : number
+>a.result : { prop: number; }
+>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
+>result : { prop: number; }
+>prop : number
+}
+
diff --git a/tests/cases/compiler/narrowingTypeofUndefined.ts b/tests/cases/compiler/narrowingTypeofUndefined.ts
@@ -0,0 +1,15 @@
+declare const a: { error: { prop: string }, result: undefined } | { error: undefined, result: { prop: number } }
+
+if (typeof a.error === 'undefined') {
+    a.result.prop; // number
+}
+else {
+    a.error.prop; // string
+}
+
+if (typeof a.error !== 'undefined') {
+    a.error.prop; // string
+}
+else {
+    a.result.prop; // number
+}