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Control flow analysis of aliased conditional expressions and discriminants #44730

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merged 5 commits into from
Jun 25, 2021
Merged

Control flow analysis of aliased conditional expressions and discriminants #44730

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08b6e2e
CFA inlining of conditional expressions referenced by const variables
ahejlsberg Jun 24, 2021
0bed057
Accept new baselines
ahejlsberg Jun 24, 2021
ad81160
Add tests
ahejlsberg Jun 25, 2021
82c601e
Accept new baselines
ahejlsberg Jun 25, 2021
9a68c4f
Increase inlining limit to 5 levels per design meeting discussion
ahejlsberg Jun 25, 2021
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126 changes: 91 additions & 35 deletions src/compiler/checker.ts
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276 changes: 276 additions & 0 deletions tests/baselines/reference/controlFlowAliasing.errors.txt
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Original file line number Diff line number Diff line change
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tests/cases/conformance/controlFlow/controlFlowAliasing.ts(61,13): error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(64,13): error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(71,13): error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(74,13): error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(82,13): error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(85,13): error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(104,13): error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(107,13): error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(124,19): error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(127,19): error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(207,13): error TS2322: Type 'string | number' is not assignable to type 'string'.
Type 'number' is not assignable to type 'string'.
tests/cases/conformance/controlFlow/controlFlowAliasing.ts(210,13): error TS2322: Type 'string | number' is not assignable to type 'number'.
Type 'string' is not assignable to type 'number'.


==== tests/cases/conformance/controlFlow/controlFlowAliasing.ts (12 errors) ====
// Narrowing by aliased conditional expressions

function f10(x: string | number) {
const isString = typeof x === "string";
if (isString) {
let t: string = x;
}
else {
let t: number = x;
}
}

function f11(x: unknown) {
const isString = typeof x === "string";
if (isString) {
let t: string = x;
}
}

function f12(x: string | number | boolean) {
const isString = typeof x === "string";
const isNumber = typeof x === "number";
if (isString || isNumber) {
let t: string | number = x;
}
else {
let t: boolean = x;
}
}

function f13(x: string | number | boolean) {
const isString = typeof x === "string";
const isNumber = typeof x === "number";
const isStringOrNumber = isString || isNumber;
if (isStringOrNumber) {
let t: string | number = x;
}
else {
let t: boolean = x;
}
}

function f14(x: number | null | undefined): number | null {
const notUndefined = x !== undefined;
return notUndefined ? x : 0;
}

function f20(obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const isFoo = obj.kind === 'foo';
if (isFoo) {
obj.foo;
}
else {
obj.bar;
}
}

function f21(obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const isFoo: boolean = obj.kind === 'foo';
if (isFoo) {
obj.foo; // Not narrowed because isFoo has type annotation
~~~
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
}
else {
obj.bar; // Not narrowed because isFoo has type annotation
~~~
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
}
}

function f22(obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
let isFoo = obj.kind === 'foo';
if (isFoo) {
obj.foo; // Not narrowed because isFoo is mutable
~~~
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
}
else {
obj.bar; // Not narrowed because isFoo is mutable
~~~
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
}
}

function f23(obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const isFoo = obj.kind === 'foo';
obj = obj;
if (isFoo) {
obj.foo; // Not narrowed because obj is assigned in function body
~~~
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
}
else {
obj.bar; // Not narrowed because obj is assigned in function body
~~~
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
}
}

function f24(arg: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const obj = arg;
const isFoo = obj.kind === 'foo';
if (isFoo) {
obj.foo;
}
else {
obj.bar;
}
}

function f25(arg: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
let obj = arg;
const isFoo = obj.kind === 'foo';
if (isFoo) {
obj.foo; // Not narrowed because obj is mutable
~~~
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
}
else {
obj.bar; // Not narrowed because obj is mutable
~~~
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
}
}

function f26(outer: { readonly obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number } }) {
const isFoo = outer.obj.kind === 'foo';
if (isFoo) {
outer.obj.foo;
}
else {
outer.obj.bar;
}
}

function f27(outer: { obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number } }) {
const isFoo = outer.obj.kind === 'foo';
if (isFoo) {
outer.obj.foo; // Not narrowed because obj is mutable
~~~
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'foo' does not exist on type '{ kind: "bar"; bar: number; }'.
}
else {
outer.obj.bar; // Not narrowed because obj is mutable
~~~
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; } | { kind: "bar"; bar: number; }'.
!!! error TS2339: Property 'bar' does not exist on type '{ kind: "foo"; foo: string; }'.
}
}

function f28(obj?: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const isFoo = obj && obj.kind === 'foo';
const isBar = obj && obj.kind === 'bar';
if (isFoo) {
obj.foo;
}
if (isBar) {
obj.bar;
}
}

// Narrowing by aliased discriminant property access

function f30(obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const kind = obj.kind;
if (kind === 'foo') {
obj.foo;
}
else {
obj.bar;
}
}

function f31(obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const { kind } = obj;
if (kind === 'foo') {
obj.foo;
}
else {
obj.bar;
}
}

function f32(obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const { kind: k } = obj;
if (k === 'foo') {
obj.foo;
}
else {
obj.bar;
}
}

function f33(obj: { kind: 'foo', foo: string } | { kind: 'bar', bar: number }) {
const { kind } = obj;
switch (kind) {
case 'foo': obj.foo; break;
case 'bar': obj.bar; break;
}
}

// Mixing of aliased discriminants and conditionals

function f40(obj: { kind: 'foo', foo?: string } | { kind: 'bar', bar?: number }) {
const { kind } = obj;
const isFoo = kind == 'foo';
if (isFoo && obj.foo) {
let t: string = obj.foo;
}
}

// Unsupported narrowing of destructured payload by destructured discriminant

type Data = { kind: 'str', payload: string } | { kind: 'num', payload: number };

function gg2(obj: Data) {
if (obj.kind === 'str') {
let t: string = obj.payload;
}
else {
let t: number = obj.payload;
}
}

function foo({ kind, payload }: Data) {
if (kind === 'str') {
let t: string = payload;
~
!!! error TS2322: Type 'string | number' is not assignable to type 'string'.
!!! error TS2322: Type 'number' is not assignable to type 'string'.
}
else {
let t: number = payload;
~
!!! error TS2322: Type 'string | number' is not assignable to type 'number'.
!!! error TS2322: Type 'string' is not assignable to type 'number'.
}
}

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