Control flow analysis for element access with variable index (#57847)

2026-02-04 12:32:08 -06:00 · 2024-03-26 13:40:28 -07:00 · 2024-03-26 13:40:28 -07:00 · a22aaf0ee7
commit a22aaf0ee7
parent 316f1805f3
7 changed files with 367 additions and 14 deletions
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@ -26622,13 +26622,20 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                return getFlowCacheKey((node as NonNullExpression | ParenthesizedExpression).expression, declaredType, initialType, flowContainer);
            case SyntaxKind.QualifiedName:
                const left = getFlowCacheKey((node as QualifiedName).left, declaredType, initialType, flowContainer);
-                return left && left + "." + (node as QualifiedName).right.escapedText;
+                return left && `${left}.${(node as QualifiedName).right.escapedText}`;
            case SyntaxKind.PropertyAccessExpression:
            case SyntaxKind.ElementAccessExpression:
                const propName = getAccessedPropertyName(node as AccessExpression);
                if (propName !== undefined) {
                    const key = getFlowCacheKey((node as AccessExpression).expression, declaredType, initialType, flowContainer);
-                    return key && key + "." + propName;
+                    return key && `${key}.${propName}`;
+                }
+                if (isElementAccessExpression(node) && isIdentifier(node.argumentExpression)) {
+                    const symbol = getResolvedSymbol(node.argumentExpression);
+                    if (isConstantVariable(symbol) || isParameterOrMutableLocalVariable(symbol) && !isSymbolAssigned(symbol)) {
+                        const key = getFlowCacheKey((node as AccessExpression).expression, declaredType, initialType, flowContainer);
+                        return key && `${key}.@${getSymbolId(symbol)}`;
+                    }
                }
                break;
            case SyntaxKind.ObjectBindingPattern:
@ -26674,9 +26681,19 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
            case SyntaxKind.PropertyAccessExpression:
            case SyntaxKind.ElementAccessExpression:
                const sourcePropertyName = getAccessedPropertyName(source as AccessExpression);
-                const targetPropertyName = isAccessExpression(target) ? getAccessedPropertyName(target) : undefined;
-                return sourcePropertyName !== undefined && targetPropertyName !== undefined && targetPropertyName === sourcePropertyName &&
-                    isMatchingReference((source as AccessExpression).expression, (target as AccessExpression).expression);
+                if (sourcePropertyName !== undefined) {
+                    const targetPropertyName = isAccessExpression(target) ? getAccessedPropertyName(target) : undefined;
+                    if (targetPropertyName !== undefined) {
+                        return targetPropertyName === sourcePropertyName && isMatchingReference((source as AccessExpression).expression, (target as AccessExpression).expression);
+                    }
+                }
+                if (isElementAccessExpression(source) && isElementAccessExpression(target) && isIdentifier(source.argumentExpression) && isIdentifier(target.argumentExpression)) {
+                    const symbol = getResolvedSymbol(source.argumentExpression);
+                    if (symbol === getResolvedSymbol(target.argumentExpression) && (isConstantVariable(symbol) || isParameterOrMutableLocalVariable(symbol) && !isSymbolAssigned(symbol))) {
+                        return isMatchingReference(source.expression, target.expression);
+                    }
+                }
+                break;
            case SyntaxKind.QualifiedName:
                return isAccessExpression(target) &&
                    (source as QualifiedName).right.escapedText === getAccessedPropertyName(target) &&
--- a/tests/baselines/reference/controlFlowComputedPropertyNames.symbols
+++ b/tests/baselines/reference/controlFlowComputedPropertyNames.symbols
@ -0,0 +1,134 @@
+//// [tests/cases/conformance/controlFlow/controlFlowComputedPropertyNames.ts] ////
+
+=== controlFlowComputedPropertyNames.ts ===
+function f1(obj: Record<string, unknown>, key: string) {
+>f1 : Symbol(f1, Decl(controlFlowComputedPropertyNames.ts, 0, 0))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 0, 12))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 0, 41))
+
+    if (typeof obj[key] === "string") {
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 0, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 0, 41))
+
+        obj[key].toUpperCase();
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 0, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 0, 41))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    }
+}
+
+function f2(obj: Record<string, string | undefined>, key: string) {
+>f2 : Symbol(f2, Decl(controlFlowComputedPropertyNames.ts, 4, 1))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 6, 12))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 6, 52))
+
+    if (obj[key] !== undefined) {
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 6, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 6, 52))
+>undefined : Symbol(undefined)
+
+        obj[key].toUpperCase();
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 6, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 6, 52))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    }
+    let key2 = key + key;
+>key2 : Symbol(key2, Decl(controlFlowComputedPropertyNames.ts, 10, 7))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 6, 52))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 6, 52))
+
+    if (obj[key2] !== undefined) {
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 6, 12))
+>key2 : Symbol(key2, Decl(controlFlowComputedPropertyNames.ts, 10, 7))
+>undefined : Symbol(undefined)
+
+        obj[key2].toUpperCase();
+>obj[key2].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 6, 12))
+>key2 : Symbol(key2, Decl(controlFlowComputedPropertyNames.ts, 10, 7))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    }
+    const key3 = key + key;
+>key3 : Symbol(key3, Decl(controlFlowComputedPropertyNames.ts, 14, 9))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 6, 52))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 6, 52))
+
+    if (obj[key3] !== undefined) {
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 6, 12))
+>key3 : Symbol(key3, Decl(controlFlowComputedPropertyNames.ts, 14, 9))
+>undefined : Symbol(undefined)
+
+        obj[key3].toUpperCase();
+>obj[key3].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 6, 12))
+>key3 : Symbol(key3, Decl(controlFlowComputedPropertyNames.ts, 14, 9))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    }
+}
+
+type Thing = { a?: string, b?: number, c?: number };
+>Thing : Symbol(Thing, Decl(controlFlowComputedPropertyNames.ts, 18, 1))
+>a : Symbol(a, Decl(controlFlowComputedPropertyNames.ts, 20, 14))
+>b : Symbol(b, Decl(controlFlowComputedPropertyNames.ts, 20, 26))
+>c : Symbol(c, Decl(controlFlowComputedPropertyNames.ts, 20, 38))
+
+function f3(obj: Thing, key: keyof Thing) {
+>f3 : Symbol(f3, Decl(controlFlowComputedPropertyNames.ts, 20, 52))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 22, 12))
+>Thing : Symbol(Thing, Decl(controlFlowComputedPropertyNames.ts, 18, 1))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 22, 23))
+>Thing : Symbol(Thing, Decl(controlFlowComputedPropertyNames.ts, 18, 1))
+
+    if (obj[key] !== undefined) {
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 22, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 22, 23))
+>undefined : Symbol(undefined)
+
+        if (typeof obj[key] === "string") {
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 22, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 22, 23))
+
+            obj[key].toUpperCase();
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 22, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 22, 23))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+        }
+        if (typeof obj[key] === "number") {
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 22, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 22, 23))
+
+            obj[key].toFixed();
+>obj[key].toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 22, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 22, 23))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+        }
+    }
+}
+
+function f4<K extends string>(obj: Record<K, string | undefined>, key: K) {
+>f4 : Symbol(f4, Decl(controlFlowComputedPropertyNames.ts, 31, 1))
+>K : Symbol(K, Decl(controlFlowComputedPropertyNames.ts, 33, 12))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 33, 30))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+>K : Symbol(K, Decl(controlFlowComputedPropertyNames.ts, 33, 12))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 33, 65))
+>K : Symbol(K, Decl(controlFlowComputedPropertyNames.ts, 33, 12))
+
+    if (obj[key]) {
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 33, 30))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 33, 65))
+
+        obj[key].toUpperCase();
+>obj[key].toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>obj : Symbol(obj, Decl(controlFlowComputedPropertyNames.ts, 33, 30))
+>key : Symbol(key, Decl(controlFlowComputedPropertyNames.ts, 33, 65))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+    }
+}
+
--- a/tests/baselines/reference/controlFlowComputedPropertyNames.types
+++ b/tests/baselines/reference/controlFlowComputedPropertyNames.types
@ -0,0 +1,163 @@
+//// [tests/cases/conformance/controlFlow/controlFlowComputedPropertyNames.ts] ////
+
+=== controlFlowComputedPropertyNames.ts ===
+function f1(obj: Record<string, unknown>, key: string) {
+>f1 : (obj: Record<string, unknown>, key: string) => void
+>obj : Record<string, unknown>
+>key : string
+
+    if (typeof obj[key] === "string") {
+>typeof obj[key] === "string" : boolean
+>typeof obj[key] : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>obj[key] : unknown
+>obj : Record<string, unknown>
+>key : string
+>"string" : "string"
+
+        obj[key].toUpperCase();
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : Record<string, unknown>
+>key : string
+>toUpperCase : () => string
+    }
+}
+
+function f2(obj: Record<string, string | undefined>, key: string) {
+>f2 : (obj: Record<string, string | undefined>, key: string) => void
+>obj : Record<string, string | undefined>
+>key : string
+
+    if (obj[key] !== undefined) {
+>obj[key] !== undefined : boolean
+>obj[key] : string | undefined
+>obj : Record<string, string | undefined>
+>key : string
+>undefined : undefined
+
+        obj[key].toUpperCase();
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : Record<string, string | undefined>
+>key : string
+>toUpperCase : () => string
+    }
+    let key2 = key + key;
+>key2 : string
+>key + key : string
+>key : string
+>key : string
+
+    if (obj[key2] !== undefined) {
+>obj[key2] !== undefined : boolean
+>obj[key2] : string | undefined
+>obj : Record<string, string | undefined>
+>key2 : string
+>undefined : undefined
+
+        obj[key2].toUpperCase();
+>obj[key2].toUpperCase() : string
+>obj[key2].toUpperCase : () => string
+>obj[key2] : string
+>obj : Record<string, string | undefined>
+>key2 : string
+>toUpperCase : () => string
+    }
+    const key3 = key + key;
+>key3 : string
+>key + key : string
+>key : string
+>key : string
+
+    if (obj[key3] !== undefined) {
+>obj[key3] !== undefined : boolean
+>obj[key3] : string | undefined
+>obj : Record<string, string | undefined>
+>key3 : string
+>undefined : undefined
+
+        obj[key3].toUpperCase();
+>obj[key3].toUpperCase() : string
+>obj[key3].toUpperCase : () => string
+>obj[key3] : string
+>obj : Record<string, string | undefined>
+>key3 : string
+>toUpperCase : () => string
+    }
+}
+
+type Thing = { a?: string, b?: number, c?: number };
+>Thing : { a?: string | undefined; b?: number | undefined; c?: number | undefined; }
+>a : string | undefined
+>b : number | undefined
+>c : number | undefined
+
+function f3(obj: Thing, key: keyof Thing) {
+>f3 : (obj: Thing, key: keyof Thing) => void
+>obj : Thing
+>key : keyof Thing
+
+    if (obj[key] !== undefined) {
+>obj[key] !== undefined : boolean
+>obj[key] : string | number | undefined
+>obj : Thing
+>key : keyof Thing
+>undefined : undefined
+
+        if (typeof obj[key] === "string") {
+>typeof obj[key] === "string" : boolean
+>typeof obj[key] : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>obj[key] : string | number
+>obj : Thing
+>key : keyof Thing
+>"string" : "string"
+
+            obj[key].toUpperCase();
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : Thing
+>key : keyof Thing
+>toUpperCase : () => string
+        }
+        if (typeof obj[key] === "number") {
+>typeof obj[key] === "number" : boolean
+>typeof obj[key] : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>obj[key] : string | number
+>obj : Thing
+>key : keyof Thing
+>"number" : "number"
+
+            obj[key].toFixed();
+>obj[key].toFixed() : string
+>obj[key].toFixed : (fractionDigits?: number | undefined) => string
+>obj[key] : number
+>obj : Thing
+>key : keyof Thing
+>toFixed : (fractionDigits?: number | undefined) => string
+        }
+    }
+}
+
+function f4<K extends string>(obj: Record<K, string | undefined>, key: K) {
+>f4 : <K extends string>(obj: Record<K, string | undefined>, key: K) => void
+>obj : Record<K, string | undefined>
+>key : K
+
+    if (obj[key]) {
+>obj[key] : Record<K, string | undefined>[K]
+>obj : Record<K, string | undefined>
+>key : K
+
+        obj[key].toUpperCase();
+>obj[key].toUpperCase() : string
+>obj[key].toUpperCase : () => string
+>obj[key] : string
+>obj : Record<K, string | undefined>
+>key : K
+>toUpperCase : () => string
+    }
+}
+
--- a/tests/baselines/reference/mappedTypeGenericIndexedAccess.types
+++ b/tests/baselines/reference/mappedTypeGenericIndexedAccess.types
@ -60,14 +60,14 @@ class Test {
 >[] : never[]
        }
        this.entries[name]?.push(entry);
->this.entries[name]?.push(entry) : number | undefined
->this.entries[name]?.push : ((...items: Types[T][]) => number) | undefined
->this.entries[name] : Types[T][] | undefined
+>this.entries[name]?.push(entry) : number
+>this.entries[name]?.push : (...items: Types[T][]) => number
+>this.entries[name] : Types[T][]
 >this.entries : { first?: { a1: true; }[] | undefined; second?: { a2: true; }[] | undefined; third?: { a3: true; }[] | undefined; }
 >this : this
 >entries : { first?: { a1: true; }[] | undefined; second?: { a2: true; }[] | undefined; third?: { a3: true; }[] | undefined; }
 >name : T
->push : ((...items: Types[T][]) => number) | undefined
+>push : (...items: Types[T][]) => number
 >entry : Types[T]
    }
 }
--- a/tests/baselines/reference/noUncheckedIndexedAccess.errors.txt
+++ b/tests/baselines/reference/noUncheckedIndexedAccess.errors.txt
@ -33,8 +33,7 @@ noUncheckedIndexedAccess.ts(90,7): error TS2322: Type 'string | undefined' is no
  Type 'undefined' is not assignable to type 'string'.
 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'.
-noUncheckedIndexedAccess.ts(99,11): error TS2322: Type 'string | undefined' is not assignable to type 'string'.
-  Type 'undefined' is not assignable to type 'string'.
+noUncheckedIndexedAccess.ts(99,11): error TS2322: Type 'undefined' is not assignable to type 'string'.


 ==== noUncheckedIndexedAccess.ts (31 errors) ====
@ -203,8 +202,7 @@ noUncheckedIndexedAccess.ts(99,11): error TS2322: Type 'string | undefined' is n
 !!! 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'.
    };
    
    
--- a/tests/baselines/reference/noUncheckedIndexedAccess.types
+++ b/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

--- a/tests/cases/conformance/controlFlow/controlFlowComputedPropertyNames.ts
+++ b/tests/cases/conformance/controlFlow/controlFlowComputedPropertyNames.ts
@ -0,0 +1,41 @@
+// @strict: true
+// @noEmit: true
+
+function f1(obj: Record<string, unknown>, key: string) {
+    if (typeof obj[key] === "string") {
+        obj[key].toUpperCase();
+    }
+}
+
+function f2(obj: Record<string, string | undefined>, key: string) {
+    if (obj[key] !== undefined) {
+        obj[key].toUpperCase();
+    }
+    let key2 = key + key;
+    if (obj[key2] !== undefined) {
+        obj[key2].toUpperCase();
+    }
+    const key3 = key + key;
+    if (obj[key3] !== undefined) {
+        obj[key3].toUpperCase();
+    }
+}
+
+type Thing = { a?: string, b?: number, c?: number };
+
+function f3(obj: Thing, key: keyof Thing) {
+    if (obj[key] !== undefined) {
+        if (typeof obj[key] === "string") {
+            obj[key].toUpperCase();
+        }
+        if (typeof obj[key] === "number") {
+            obj[key].toFixed();
+        }
+    }
+}
+
+function f4<K extends string>(obj: Record<K, string | undefined>, key: K) {
+    if (obj[key]) {
+        obj[key].toUpperCase();
+    }
+}