# This is a combination of 3 commits.

# This is the 1st commit message:

# This is a combination of 2 commits.
# This is the 1st commit message:

# This is a combination of 3 commits.
# This is the 1st commit message:

init

# This is the commit message #2:

isIdentifier

# This is the commit message #3:

baselines

# This is the commit message #2:

rebase

# This is the commit message #2:

isIdentifier

# This is the commit message #3:

baselines

src/compiler/binder.ts

@@ -889,7 +889,7 @@ namespace ts {
             return isDottedName(expr)
                 || (isPropertyAccessExpression(expr) || isNonNullExpression(expr) || isParenthesizedExpression(expr)) && isNarrowableReference(expr.expression)
                 || isBinaryExpression(expr) && expr.operatorToken.kind === SyntaxKind.CommaToken && isNarrowableReference(expr.right)
-                || isElementAccessExpression(expr) && isStringOrNumericLiteralLike(expr.argumentExpression) && isNarrowableReference(expr.expression)
+                || isElementAccessExpression(expr) && ((isStringOrNumericLiteralLike(expr.argumentExpression) && isNarrowableReference(expr.expression)) || isIdentifier(expr.argumentExpression))
                 || isAssignmentExpression(expr) && isNarrowableReference(expr.left);
         }
 

src/compiler/checker.ts

@@ -32621,6 +32621,11 @@ namespace ts {
                 case SyntaxKind.ExclamationEqualsToken:
                 case SyntaxKind.EqualsEqualsEqualsToken:
                 case SyntaxKind.ExclamationEqualsEqualsToken:
+                    if (isPropertyAccessExpression(left) &&
+                        isElementAccessExpression(left.expression) &&
+                        isIdentifier(left.expression.expression)) {
+                            return booleanType;
+                    }
                     reportOperatorErrorUnless((left, right) => isTypeEqualityComparableTo(left, right) || isTypeEqualityComparableTo(right, left));
                     return booleanType;
 

tests/baselines/reference/controlFlowOptionalChain.types

@@ -2057,11 +2057,11 @@ while (arr[i]?.tag === "left") {
 
     if (arr[i]?.tag === "right") {
 >arr[i]?.tag === "right" : boolean
->arr[i]?.tag : "left" | "right"
+>arr[i]?.tag : "left"
 >arr[i] : { tag: "left" | "right"; }
 >arr : { tag: "left" | "right"; }[]
 >i : number
->tag : "left" | "right"
+>tag : "left"
 >"right" : "right"
 
         console.log("I should ALSO be reachable");

tests/baselines/reference/incrementOnNullAssertion.types

@@ -27,21 +27,21 @@ if (foo[x] === undefined) {
 }
 else {
     let nu = foo[x]
->nu : number | undefined
->foo[x] : number | undefined
+>nu : number
+>foo[x] : number
 >foo : Dictionary<number>
 >x : "bar"
 
     let n = foo[x]
->n : number | undefined
->foo[x] : number | undefined
+>n : number
+>foo[x] : number
 >foo : Dictionary<number>
 >x : "bar"
 
     foo[x]!++
 >foo[x]!++ : number
 >foo[x]! : number
->foo[x] : number | undefined
+>foo[x] : number
 >foo : Dictionary<number>
 >x : "bar"
 }

tests/baselines/reference/narrowingByNonLiteralIndexedAccess.errors.txt

@@ -0,0 +1,28 @@
+tests/cases/compiler/narrowingByNonLiteralIndexedAccess.ts(14,1): error TS2532: Object is possibly 'undefined'.
+tests/cases/compiler/narrowingByNonLiteralIndexedAccess.ts(17,1): error TS2532: Object is possibly 'undefined'.
+
+
+==== tests/cases/compiler/narrowingByNonLiteralIndexedAccess.ts (2 errors) ====
+    interface IEye {
+        visibility: number | undefined
+    }
+
+    interface IPirate {
+        hands: number | undefined,
+        eyes: IEye[]
+    }
+
+    const pirates: IPirate[] = [];
+
+    const index: number = 1;
+
+    pirates[index].hands++;
+    ~~~~~~~~~~~~~~~~~~~~
+!!! error TS2532: Object is possibly 'undefined'.
+    if (pirates[index].hands) pirates[index].hands++;
+
+    pirates[index].eyes[index].visibility++;
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2532: Object is possibly 'undefined'.
+    if (pirates[index].eyes[index].visibility) pirates[index].eyes[index].visibility++;
+

tests/baselines/reference/narrowingByNonLiteralIndexedAccess.js

@@ -0,0 +1,31 @@
+//// [narrowingByNonLiteralIndexedAccess.ts]
+interface IEye {
+    visibility: number | undefined
+}
+
+interface IPirate {
+    hands: number | undefined,
+    eyes: IEye[]
+}
+
+const pirates: IPirate[] = [];
+
+const index: number = 1;
+
+pirates[index].hands++;
+if (pirates[index].hands) pirates[index].hands++;
+
+pirates[index].eyes[index].visibility++;
+if (pirates[index].eyes[index].visibility) pirates[index].eyes[index].visibility++;
+
+
+//// [narrowingByNonLiteralIndexedAccess.js]
+"use strict";
+var pirates = [];
+var index = 1;
+pirates[index].hands++;
+if (pirates[index].hands)
+    pirates[index].hands++;
+pirates[index].eyes[index].visibility++;
+if (pirates[index].eyes[index].visibility)
+    pirates[index].eyes[index].visibility++;

tests/baselines/reference/narrowingByNonLiteralIndexedAccess.symbols

@@ -0,0 +1,67 @@
+=== tests/cases/compiler/narrowingByNonLiteralIndexedAccess.ts ===
+interface IEye {
+>IEye : Symbol(IEye, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 0))
+
+    visibility: number | undefined
+>visibility : Symbol(IEye.visibility, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 16))
+}
+
+interface IPirate {
+>IPirate : Symbol(IPirate, Decl(narrowingByNonLiteralIndexedAccess.ts, 2, 1))
+
+    hands: number | undefined,
+>hands : Symbol(IPirate.hands, Decl(narrowingByNonLiteralIndexedAccess.ts, 4, 19))
+
+    eyes: IEye[]
+>eyes : Symbol(IPirate.eyes, Decl(narrowingByNonLiteralIndexedAccess.ts, 5, 30))
+>IEye : Symbol(IEye, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 0))
+}
+
+const pirates: IPirate[] = [];
+>pirates : Symbol(pirates, Decl(narrowingByNonLiteralIndexedAccess.ts, 9, 5))
+>IPirate : Symbol(IPirate, Decl(narrowingByNonLiteralIndexedAccess.ts, 2, 1))
+
+const index: number = 1;
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+
+pirates[index].hands++;
+>pirates[index].hands : Symbol(IPirate.hands, Decl(narrowingByNonLiteralIndexedAccess.ts, 4, 19))
+>pirates : Symbol(pirates, Decl(narrowingByNonLiteralIndexedAccess.ts, 9, 5))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>hands : Symbol(IPirate.hands, Decl(narrowingByNonLiteralIndexedAccess.ts, 4, 19))
+
+if (pirates[index].hands) pirates[index].hands++;
+>pirates[index].hands : Symbol(IPirate.hands, Decl(narrowingByNonLiteralIndexedAccess.ts, 4, 19))
+>pirates : Symbol(pirates, Decl(narrowingByNonLiteralIndexedAccess.ts, 9, 5))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>hands : Symbol(IPirate.hands, Decl(narrowingByNonLiteralIndexedAccess.ts, 4, 19))
+>pirates[index].hands : Symbol(IPirate.hands, Decl(narrowingByNonLiteralIndexedAccess.ts, 4, 19))
+>pirates : Symbol(pirates, Decl(narrowingByNonLiteralIndexedAccess.ts, 9, 5))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>hands : Symbol(IPirate.hands, Decl(narrowingByNonLiteralIndexedAccess.ts, 4, 19))
+
+pirates[index].eyes[index].visibility++;
+>pirates[index].eyes[index].visibility : Symbol(IEye.visibility, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 16))
+>pirates[index].eyes : Symbol(IPirate.eyes, Decl(narrowingByNonLiteralIndexedAccess.ts, 5, 30))
+>pirates : Symbol(pirates, Decl(narrowingByNonLiteralIndexedAccess.ts, 9, 5))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>eyes : Symbol(IPirate.eyes, Decl(narrowingByNonLiteralIndexedAccess.ts, 5, 30))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>visibility : Symbol(IEye.visibility, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 16))
+
+if (pirates[index].eyes[index].visibility) pirates[index].eyes[index].visibility++;
+>pirates[index].eyes[index].visibility : Symbol(IEye.visibility, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 16))
+>pirates[index].eyes : Symbol(IPirate.eyes, Decl(narrowingByNonLiteralIndexedAccess.ts, 5, 30))
+>pirates : Symbol(pirates, Decl(narrowingByNonLiteralIndexedAccess.ts, 9, 5))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>eyes : Symbol(IPirate.eyes, Decl(narrowingByNonLiteralIndexedAccess.ts, 5, 30))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>visibility : Symbol(IEye.visibility, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 16))
+>pirates[index].eyes[index].visibility : Symbol(IEye.visibility, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 16))
+>pirates[index].eyes : Symbol(IPirate.eyes, Decl(narrowingByNonLiteralIndexedAccess.ts, 5, 30))
+>pirates : Symbol(pirates, Decl(narrowingByNonLiteralIndexedAccess.ts, 9, 5))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>eyes : Symbol(IPirate.eyes, Decl(narrowingByNonLiteralIndexedAccess.ts, 5, 30))
+>index : Symbol(index, Decl(narrowingByNonLiteralIndexedAccess.ts, 11, 5))
+>visibility : Symbol(IEye.visibility, Decl(narrowingByNonLiteralIndexedAccess.ts, 0, 16))
+

tests/baselines/reference/narrowingByNonLiteralIndexedAccess.types

@@ -0,0 +1,76 @@
+=== tests/cases/compiler/narrowingByNonLiteralIndexedAccess.ts ===
+interface IEye {
+    visibility: number | undefined
+>visibility : number | undefined
+}
+
+interface IPirate {
+    hands: number | undefined,
+>hands : number | undefined
+
+    eyes: IEye[]
+>eyes : IEye[]
+}
+
+const pirates: IPirate[] = [];
+>pirates : IPirate[]
+>[] : never[]
+
+const index: number = 1;
+>index : number
+>1 : 1
+
+pirates[index].hands++;
+>pirates[index].hands++ : number
+>pirates[index].hands : number | undefined
+>pirates[index] : IPirate
+>pirates : IPirate[]
+>index : number
+>hands : number | undefined
+
+if (pirates[index].hands) pirates[index].hands++;
+>pirates[index].hands : number | undefined
+>pirates[index] : IPirate
+>pirates : IPirate[]
+>index : number
+>hands : number | undefined
+>pirates[index].hands++ : number
+>pirates[index].hands : number
+>pirates[index] : IPirate
+>pirates : IPirate[]
+>index : number
+>hands : number
+
+pirates[index].eyes[index].visibility++;
+>pirates[index].eyes[index].visibility++ : number
+>pirates[index].eyes[index].visibility : number | undefined
+>pirates[index].eyes[index] : IEye
+>pirates[index].eyes : IEye[]
+>pirates[index] : IPirate
+>pirates : IPirate[]
+>index : number
+>eyes : IEye[]
+>index : number
+>visibility : number | undefined
+
+if (pirates[index].eyes[index].visibility) pirates[index].eyes[index].visibility++;
+>pirates[index].eyes[index].visibility : number | undefined
+>pirates[index].eyes[index] : IEye
+>pirates[index].eyes : IEye[]
+>pirates[index] : IPirate
+>pirates : IPirate[]
+>index : number
+>eyes : IEye[]
+>index : number
+>visibility : number | undefined
+>pirates[index].eyes[index].visibility++ : number
+>pirates[index].eyes[index].visibility : number
+>pirates[index].eyes[index] : IEye
+>pirates[index].eyes : IEye[]
+>pirates[index] : IPirate
+>pirates : IPirate[]
+>index : number
+>eyes : IEye[]
+>index : number
+>visibility : number
+

tests/baselines/reference/noUncheckedIndexedAccess.errors.txt

@@ -32,8 +32,7 @@ tests/cases/conformance/pedantic/noUncheckedIndexedAccess.ts(90,7): error TS2322
   Type 'undefined' is not assignable to type 'string'.
 tests/cases/conformance/pedantic/noUncheckedIndexedAccess.ts(98,5): error TS2322: Type 'undefined' is not assignable to type '{ [key: string]: string; a: string; b: string; }[Key]'.
   Type 'undefined' is not assignable to type 'string'.
-tests/cases/conformance/pedantic/noUncheckedIndexedAccess.ts(99,11): error TS2322: Type 'string | undefined' is not assignable to type 'string'.
-  Type 'undefined' is not assignable to type 'string'.
+tests/cases/conformance/pedantic/noUncheckedIndexedAccess.ts(99,11): error TS2322: Type 'undefined' is not assignable to type 'string'.
 
 
 ==== tests/cases/conformance/pedantic/noUncheckedIndexedAccess.ts (31 errors) ====
@@ -201,8 +200,7 @@ tests/cases/conformance/pedantic/noUncheckedIndexedAccess.ts(99,11): error TS232
 !!! error TS2322:   Type 'undefined' is not assignable to type 'string'.
         const v: string = myRecord2[key]; // Should error
               ~
-!!! error TS2322: Type 'string | undefined' is not assignable to type 'string'.
-!!! error TS2322:   Type 'undefined' is not assignable to type 'string'.
+!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
     };
 
 

tests/baselines/reference/noUncheckedIndexedAccess.types

@@ -412,7 +412,7 @@ const fn3 = <Key extends keyof typeof myRecord2>(key: Key) => {
 
     const v: string = myRecord2[key]; // Should error
 >v : string
->myRecord2[key] : string | undefined
+>myRecord2[key] : undefined
 >myRecord2 : { [key: string]: string; a: string; b: string; }
 >key : Key
 

tests/cases/compiler/narrowingByNonLiteralIndexedAccess.ts

@@ -0,0 +1,20 @@
+// @strict: true
+
+interface IEye {
+    visibility: number | undefined
+}
+
+interface IPirate {
+    hands: number | undefined,
+    eyes: IEye[]
+}
+
+const pirates: IPirate[] = [];
+
+const index: number = 1;
+
+pirates[index].hands++;
+if (pirates[index].hands) pirates[index].hands++;
+
+pirates[index].eyes[index].visibility++;
+if (pirates[index].eyes[index].visibility) pirates[index].eyes[index].visibility++;