[ts 4.7] Support optional variance annotations

packages/babel-generator/src/generators/typescript.ts

@@ -25,6 +25,16 @@ export function TSTypeParameterInstantiation(
 export { TSTypeParameterInstantiation as TSTypeParameterDeclaration };
 
 export function TSTypeParameter(this: Printer, node: t.TSTypeParameter) {
+  if (node.in) {
+    this.word("in");
+    this.space();
+  }
+
+  if (node.out) {
+    this.word("out");
+    this.space();
+  }
+
   this.word(
     !process.env.BABEL_8_BREAKING
       ? (node.name as unknown as string)

packages/babel-generator/test/fixtures/typescript/variance-annotations-with-jsx/input.tsx

@@ -0,0 +1,94 @@
+// valid JSX
+<in T>() => {}</in>;
+
+type Covariant<out T> = {
+    x: T;
+}
+
+declare let super_covariant: Covariant<unknown>;
+declare let sub_covariant: Covariant<string>;
+
+super_covariant = sub_covariant;
+sub_covariant = super_covariant;  // Error
+
+type Contravariant<in T> = {
+    f: (x: T) => void;
+}
+
+declare let super_contravariant: Contravariant<unknown>;
+declare let sub_contravariant: Contravariant<string>;
+
+super_contravariant = sub_contravariant;  // Error
+sub_contravariant = super_contravariant;
+
+type Invariant<in out T> = {
+    f: (x: T) => T;
+}
+
+declare let super_invariant: Invariant<unknown>;
+declare let sub_invariant: Invariant<string>;
+
+super_invariant = sub_invariant;  // Error
+sub_invariant = super_invariant;  // Error
+
+// Variance of various type constructors
+
+type T10<out T> = T;
+type T11<in T> = keyof T;
+type T12<out T, out K extends keyof T> = T[K];
+type T13<in out T> = T[keyof T];
+
+// Variance annotation errors
+
+type Covariant1<in T> = {  // Error
+    x: T;
+}
+
+type Contravariant1<out T> = keyof T;  // Error
+
+type Contravariant2<out T> = {  // Error
+    f: (x: T) => void;
+}
+
+type Invariant1<in T> = {  // Error
+    f: (x: T) => T;
+}
+
+type Invariant2<out T> = {  // Error
+    f: (x: T) => T;
+}
+
+// Variance in circular types
+
+type Foo1<in T> = {  // Error
+    x: T;
+    f: FooFn1<T>;
+}
+
+type FooFn1<T> = (foo: Bar1<T[]>) => void;
+
+type Bar1<T> = {
+    value: Foo1<T[]>;
+}
+
+type Foo2<out T> = {  // Error
+    x: T;
+    f: FooFn2<T>;
+}
+
+type FooFn2<T> = (foo: Bar2<T[]>) => void;
+
+type Bar2<T> = {
+    value: Foo2<T[]>;
+}
+
+type Foo3<in out T> = {
+    x: T;
+    f: FooFn3<T>;
+}
+
+type FooFn3<T> = (foo: Bar3<T[]>) => void;
+
+type Bar3<T> = {
+    value: Foo3<T[]>;
+}

packages/babel-generator/test/fixtures/typescript/variance-annotations-with-jsx/options.json

@@ -0,0 +1,4 @@
+{
+  "BABEL_8_BREAKING": false,
+  "plugins": ["jsx", "typescript"]
+}

packages/babel-generator/test/fixtures/typescript/variance-annotations-with-jsx/output.js

@@ -0,0 +1,78 @@
+// valid JSX
+<in T>() => {}</in>;
+type Covariant<out T> = {
+  x: T;
+};
+declare let super_covariant: Covariant<unknown>;
+declare let sub_covariant: Covariant<string>;
+super_covariant = sub_covariant;
+sub_covariant = super_covariant; // Error
+
+type Contravariant<in T> = {
+  f: (x: T) => void;
+};
+declare let super_contravariant: Contravariant<unknown>;
+declare let sub_contravariant: Contravariant<string>;
+super_contravariant = sub_contravariant; // Error
+
+sub_contravariant = super_contravariant;
+type Invariant<in out T> = {
+  f: (x: T) => T;
+};
+declare let super_invariant: Invariant<unknown>;
+declare let sub_invariant: Invariant<string>;
+super_invariant = sub_invariant; // Error
+
+sub_invariant = super_invariant; // Error
+// Variance of various type constructors
+
+type T10<out T> = T;
+type T11<in T> = keyof T;
+type T12<out T, out K extends keyof T> = T[K];
+type T13<in out T> = T[keyof T]; // Variance annotation errors
+
+type Covariant1<in T> = {
+  // Error
+  x: T;
+};
+type Contravariant1<out T> = keyof T; // Error
+
+type Contravariant2<out T> = {
+  // Error
+  f: (x: T) => void;
+};
+type Invariant1<in T> = {
+  // Error
+  f: (x: T) => T;
+};
+type Invariant2<out T> = {
+  // Error
+  f: (x: T) => T;
+}; // Variance in circular types
+
+type Foo1<in T> = {
+  // Error
+  x: T;
+  f: FooFn1<T>;
+};
+type FooFn1<T> = (foo: Bar1<T[]>) => void;
+type Bar1<T> = {
+  value: Foo1<T[]>;
+};
+type Foo2<out T> = {
+  // Error
+  x: T;
+  f: FooFn2<T>;
+};
+type FooFn2<T> = (foo: Bar2<T[]>) => void;
+type Bar2<T> = {
+  value: Foo2<T[]>;
+};
+type Foo3<in out T> = {
+  x: T;
+  f: FooFn3<T>;
+};
+type FooFn3<T> = (foo: Bar3<T[]>) => void;
+type Bar3<T> = {
+  value: Foo3<T[]>;
+};

packages/babel-parser/src/plugins/typescript/index.js

@@ -47,7 +47,8 @@ type TsModifier =
   | "declare"
   | "static"
   | "override"
-  | N.Accessibility;
+  | N.Accessibility
+  | N.VarianceAnnotations;
 
 function nonNull<T>(x: ?T): T {
   if (x == null) {
@@ -153,6 +154,14 @@ const TSErrors = ParseErrorEnum`typescript`(_ => ({
   InvalidModifierOnTypeMember: _<{| modifier: TsModifier |}>(
     ({ modifier }) => `'${modifier}' modifier cannot appear on a type member.`,
   ),
+  InvalidModifierOnTypeParameter: _<{| modifier: TsModifier |}>(
+    ({ modifier }) =>
+      `'${modifier}' modifier cannot appear on a type parameter.`,
+  ),
+  InvalidModifierOnTypeParameterPositions: _<{| modifier: TsModifier |}>(
+    ({ modifier }) =>
+      `'${modifier}' modifier can only appear on a type parameter of a class, interface or type alias.`,
+  ),
   InvalidModifiersOrder: _<{| orderedModifiers: [TsModifier, TsModifier] |}>(
     ({ orderedModifiers }) =>
       `'${orderedModifiers[0]}' modifier must precede '${orderedModifiers[1]}' modifier.`,
@@ -286,6 +295,10 @@ function tsIsAccessModifier(modifier: string): boolean %checks {
   );
 }
 
+function tsIsVarianceAnnotations(modifier: string): boolean %checks {
+  return modifier === "in" || modifier === "out";
+}
+
 export default (superClass: Class<Parser>): Class<Parser> =>
   class extends superClass {
     getScopeHandler(): Class<TypeScriptScopeHandler> {
@@ -324,7 +337,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       allowedModifiers: T[],
       stopOnStartOfClassStaticBlock?: boolean,
     ): ?T {
-      if (!tokenIsIdentifier(this.state.type)) {
+      if (!tokenIsIdentifier(this.state.type) && this.state.type !== tt._in) {
         return undefined;
       }
 
@@ -350,6 +363,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       allowedModifiers,
       disallowedModifiers,
       stopOnStartOfClassStaticBlock,
+      errorTemplate = TSErrors.InvalidModifierOnTypeMember,
     }: {
       modified: {
         [key: TsModifier]: ?true,
@@ -358,6 +372,8 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       allowedModifiers: TsModifier[],
       disallowedModifiers?: TsModifier[],
       stopOnStartOfClassStaticBlock?: boolean,
+      // FIXME: make sure errorTemplate can receive `modifier`
+      errorTemplate?: any,
     }): void {
       const enforceOrder = (loc, modifier, before, after) => {
         if (modifier === before && modified[after]) {
@@ -401,6 +417,13 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
             modified.accessibility = modifier;
           }
+        } else if (tsIsVarianceAnnotations(modifier)) {
+          if (modified[modifier]) {
+            this.raise(TSErrors.DuplicateModifier, { at: startLoc, modifier });
+          }
+          modified[modifier] = true;
+
+          enforceOrder(startLoc, modifier, "in", "out");
         } else {
           if (Object.hasOwnProperty.call(modified, modifier)) {
             this.raise(TSErrors.DuplicateModifier, { at: startLoc, modifier });
@@ -417,7 +440,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         }
 
         if (disallowedModifiers?.includes(modifier)) {
-          this.raise(TSErrors.InvalidModifierOnTypeMember, {
+          this.raise(errorTemplate, {
             at: startLoc,
             modifier,
           });
@@ -614,21 +637,57 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       return this.finishNode(node, "TSTypeQuery");
     }
 
-    tsParseTypeParameter(): N.TsTypeParameter {
+    tsParseInOutModifiers(node: N.TsTypeParameter) {
+      this.tsParseModifiers({
+        modified: node,
+        allowedModifiers: ["in", "out"],
+        disallowedModifiers: [
+          "public",
+          "private",
+          "protected",
+          "readonly",
+          "declare",
+          "abstract",
+          "override",
+        ],
+        errorTemplate: TSErrors.InvalidModifierOnTypeParameter,
+      });
+    }
+
+    // for better error recover
+    tsParseNoneModifiers(node: N.TsTypeParameter) {
+      this.tsParseModifiers({
+        modified: node,
+        allowedModifiers: [],
+        disallowedModifiers: ["in", "out"],
+        errorTemplate: TSErrors.InvalidModifierOnTypeParameterPositions,
+      });
+    }
+
+    tsParseTypeParameter(
+      parseModifiers: (
+        node: N.TsTypeParameter,
+      ) => void = this.tsParseNoneModifiers.bind(this),
+    ): N.TsTypeParameter {
       const node: N.TsTypeParameter = this.startNode();
+
+      parseModifiers(node);
+
       node.name = this.tsParseTypeParameterName();
       node.constraint = this.tsEatThenParseType(tt._extends);
       node.default = this.tsEatThenParseType(tt.eq);
       return this.finishNode(node, "TSTypeParameter");
     }
 
-    tsTryParseTypeParameters(): ?N.TsTypeParameterDeclaration {
+    tsTryParseTypeParameters(
+      parseModifiers: ?(node: N.TsTypeParameter) => void,
+    ): ?N.TsTypeParameterDeclaration {
       if (this.match(tt.lt)) {
-        return this.tsParseTypeParameters();
+        return this.tsParseTypeParameters(parseModifiers);
       }
     }
 
-    tsParseTypeParameters() {
+    tsParseTypeParameters(parseModifiers: ?(node: N.TsTypeParameter) => void) {
       const node: N.TsTypeParameterDeclaration = this.startNode();
 
       if (this.match(tt.lt) || this.match(tt.jsxTagStart)) {
@@ -641,7 +700,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
       node.params = this.tsParseBracketedList(
         "TypeParametersOrArguments",
-        this.tsParseTypeParameter.bind(this),
+        this.tsParseTypeParameter.bind(this, parseModifiers),
         /* bracket */ false,
         /* skipFirstToken */ true,
         refTrailingCommaPos,
@@ -1599,7 +1658,9 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         this.raise(TSErrors.MissingInterfaceName, { at: this.state.startLoc });
       }
 
-      node.typeParameters = this.tsTryParseTypeParameters();
+      node.typeParameters = this.tsTryParseTypeParameters(
+        this.tsParseInOutModifiers.bind(this),
+      );
       if (this.eat(tt._extends)) {
         node.extends = this.tsParseHeritageClause("extends");
       }
@@ -1614,8 +1675,12 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     ): N.TsTypeAliasDeclaration {
       node.id = this.parseIdentifier();
       this.checkIdentifier(node.id, BIND_TS_TYPE);
+
       node.typeAnnotation = this.tsInType(() => {
-        node.typeParameters = this.tsTryParseTypeParameters();
+        node.typeParameters = this.tsTryParseTypeParameters(
+          this.tsParseInOutModifiers.bind(this),
+        );
+
         this.expect(tt.eq);
 
         if (
@@ -2640,7 +2705,9 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       this.tsParseModifiers({
         modified: member,
         allowedModifiers: modifiers,
+        disallowedModifiers: ["in", "out"],
         stopOnStartOfClassStaticBlock: true,
+        errorTemplate: TSErrors.InvalidModifierOnTypeParameterPositions,
       });
 
       const callParseClassMemberWithIsStatic = () => {
@@ -2876,7 +2943,9 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         optionalId,
         (node: any).declare ? BIND_TS_AMBIENT : BIND_CLASS,
       );
-      const typeParameters = this.tsTryParseTypeParameters();
+      const typeParameters = this.tsTryParseTypeParameters(
+        this.tsParseInOutModifiers.bind(this),
+      );
       if (typeParameters) node.typeParameters = typeParameters;
     }