TypeScript: Support conditional types syntax (#7404)

Microsoft/TypeScript#21316 and Microsoft/TypeScript#21496

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

@@ -256,6 +256,28 @@ export function tsPrintUnionOrIntersectionType(node, sep) {
   });
 }
 
+export function TSConditionalType(node) {
+  this.print(node.checkType);
+  this.space();
+  this.word("extends");
+  this.space();
+  this.print(node.extendsType);
+  this.space();
+  this.token("?");
+  this.space();
+  this.print(node.trueType);
+  this.space();
+  this.token(":");
+  this.space();
+  this.print(node.falseType);
+}
+
+export function TSInferType(node) {
+  this.token("infer");
+  this.space();
+  this.print(node.typeParameter);
+}
+
 export function TSParenthesizedType(node) {
   this.token("(");
   this.print(node.typeAnnotation, node);

packages/babel-generator/test/fixtures/typescript/types-conditional-infer/input.js

@@ -0,0 +1 @@
+type Element<T> = T extends (infer U)[] ? U : T;

packages/babel-generator/test/fixtures/typescript/types-conditional-infer/output.js

@@ -0,0 +1 @@
+type Element<T> = T extends (infer U)[] ? U : T;

packages/babel-generator/test/fixtures/typescript/types-conditional/input.js

@@ -0,0 +1 @@
+let x: number extends string ? boolean : null;

packages/babel-generator/test/fixtures/typescript/types-conditional/output.js

@@ -0,0 +1 @@
+let x: number extends string ? boolean : null;

packages/babel-types/README.md

@@ -1875,6 +1875,22 @@ Aliases: `TSTypeElement`
 
 ---
 
+### tSConditionalType
+```javascript
+t.tsConditionalType(checkType, extendsType, trueType, falseType)
+```
+
+See also `t.isTSConditionalType(node, opts)` and `t.assertTSConditionalType(node, opts)`.
+
+Aliases: `TSType`
+
+ - `checkType`: `TSType` (required)
+ - `extendsType`: `TSType` (required)
+ - `trueType`: `TSType` (required)
+ - `falseType`: `TSType` (required)
+
+---
+
 ### tSConstructSignatureDeclaration
 ```javascript
 t.tsConstructSignatureDeclaration(typeParameters, parameters, typeAnnotation)
@@ -2074,6 +2090,19 @@ Aliases: `TSType`
 
 ---
 
+### tSInferType
+```javascript
+t.tsInferType(typeParameter)
+```
+
+See also `t.isTSInferType(node, opts)` and `t.assertTSInferType(node, opts)`.
+
+Aliases: `TSType`
+
+ - `typeParameter`: `TSType` (required)
+
+---
+
 ### tSInterfaceBody
 ```javascript
 t.tsInterfaceBody(body)

packages/babel-types/src/asserts/generated/index.js

@@ -801,6 +801,15 @@ export function assertTSIntersectionType(
 ): void {
   assert("TSIntersectionType", node, opts);
 }
+export function assertTSConditionalType(
+  node: Object,
+  opts?: Object = {},
+): void {
+  assert("TSConditionalType", node, opts);
+}
+export function assertTSInferType(node: Object, opts?: Object = {}): void {
+  assert("TSInferType", node, opts);
+}
 export function assertTSParenthesizedType(
   node: Object,
   opts?: Object = {},

packages/babel-types/src/builders/generated/index.js

@@ -774,6 +774,16 @@ export function TSIntersectionType(...args: Array<any>): Object {
 }
 export { TSIntersectionType as tsIntersectionType };
 export { TSIntersectionType as tSIntersectionType };
+export function TSConditionalType(...args: Array<any>): Object {
+  return builder("TSConditionalType", ...args);
+}
+export { TSConditionalType as tsConditionalType };
+export { TSConditionalType as tSConditionalType };
+export function TSInferType(...args: Array<any>): Object {
+  return builder("TSInferType", ...args);
+}
+export { TSInferType as tsInferType };
+export { TSInferType as tSInferType };
 export function TSParenthesizedType(...args: Array<any>): Object {
   return builder("TSParenthesizedType", ...args);
 }

packages/babel-types/src/definitions/typescript.js

@@ -223,6 +223,25 @@ const unionOrIntersection = {
 defineType("TSUnionType", unionOrIntersection);
 defineType("TSIntersectionType", unionOrIntersection);
 
+defineType("TSConditionalType", {
+  aliases: ["TSType"],
+  visitor: ["checkType", "extendsType", "trueType", "falseType"],
+  fields: {
+    checkType: validateType("TSType"),
+    extendsType: validateType("TSType"),
+    trueType: validateType("TSType"),
+    falseType: validateType("TSType"),
+  },
+});
+
+defineType("TSInferType", {
+  aliases: ["TSType"],
+  visitor: ["typeParameter"],
+  fields: {
+    typeParameter: validateType("TSType"),
+  },
+});
+
 defineType("TSParenthesizedType", {
   aliases: ["TSType"],
   visitor: ["typeAnnotation"],

packages/babel-types/src/validators/generated/index.js

@@ -608,6 +608,12 @@ export function isTSUnionType(node: Object, opts?: Object): boolean {
 export function isTSIntersectionType(node: Object, opts?: Object): boolean {
   return is("TSIntersectionType", node, opts);
 }
+export function isTSConditionalType(node: Object, opts?: Object): boolean {
+  return is("TSConditionalType", node, opts);
+}
+export function isTSInferType(node: Object, opts?: Object): boolean {
+  return is("TSInferType", node, opts);
+}
 export function isTSParenthesizedType(node: Object, opts?: Object): boolean {
   return is("TSParenthesizedType", node, opts);
 }

packages/babylon/src/plugins/typescript.js

@@ -617,11 +617,22 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       return this.finishNode(node, "TSTypeOperator");
     }
 
+    tsParseInferType(): N.TsInferType {
+      const node = this.startNode();
+      this.expectContextual("infer");
+      const typeParameter = this.startNode();
+      typeParameter.name = this.parseIdentifierName(typeParameter.start);
+      node.typeParameter = this.finishNode(typeParameter, "TypeParameter");
+      return this.finishNode(node, "TSInferType");
+    }
+
     tsParseTypeOperatorOrHigher(): N.TsType {
       const operator = ["keyof", "unique"].find(kw => this.isContextual(kw));
       return operator
         ? this.tsParseTypeOperator(operator)
-        : this.tsParseArrayTypeOrHigher();
+        : this.isContextual("infer")
+          ? this.tsParseInferType()
+          : this.tsParseArrayTypeOrHigher();
     }
 
     tsParseUnionOrIntersectionType(
@@ -774,6 +785,21 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     tsParseType(): N.TsType {
       // Need to set `state.inType` so that we don't parse JSX in a type context.
       assert(this.state.inType);
+      const type = this.tsParseNonConditionalType();
+      if (this.hasPrecedingLineBreak() || !this.eat(tt._extends)) {
+        return type;
+      }
+      const node: N.TsConditionalType = this.startNodeAtNode(type);
+      node.checkType = type;
+      node.extendsType = this.tsParseNonConditionalType();
+      this.expect(tt.question);
+      node.trueType = this.tsParseType();
+      this.expect(tt.colon);
+      node.falseType = this.tsParseType();
+      return this.finishNode(node, "TSConditionalType");
+    }
+
+    tsParseNonConditionalType(): N.TsType {
       if (this.tsIsStartOfFunctionType()) {
         return this.tsParseFunctionOrConstructorType("TSFunctionType");
       }

packages/babylon/src/types.js

@@ -1154,6 +1154,19 @@ export type TsIntersectionType = TsUnionOrIntersectionTypeBase & {
   type: "TSIntersectionType",
 };
 
+export type TsConditionalType = TsTypeBase & {
+  type: "TSConditionalType",
+  checkType: TsType,
+  extendsType: TsType,
+  trueType: TsType,
+  falseType: tsType,
+};
+
+export type InferType = TsTypeBase & {
+  type: "TSInferType",
+  typeParameter: TypeParameter,
+};
+
 export type TsParenthesizedType = TsTypeBase & {
   type: "TSParenthesizedType",
   typeAnnotation: TsType,

packages/babylon/test/fixtures/typescript/types/conditional-infer/input.js

@@ -0,0 +1 @@
+type Element<T> = T extends (infer U)[] ? U : T;

packages/babylon/test/fixtures/typescript/types/conditional-infer/output.json

@@ -0,0 +1,271 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 48,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 48
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 48,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 48
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "TSTypeAliasDeclaration",
+        "start": 0,
+        "end": 48,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 48
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 5,
+          "end": 12,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 5
+            },
+            "end": {
+              "line": 1,
+              "column": 12
+            },
+            "identifierName": "Element"
+          },
+          "name": "Element"
+        },
+        "typeParameters": {
+          "type": "TSTypeParameterDeclaration",
+          "start": 12,
+          "end": 15,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 12
+            },
+            "end": {
+              "line": 1,
+              "column": 15
+            }
+          },
+          "params": [
+            {
+              "type": "TSTypeParameter",
+              "start": 13,
+              "end": 14,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 13
+                },
+                "end": {
+                  "line": 1,
+                  "column": 14
+                }
+              },
+              "name": "T"
+            }
+          ]
+        },
+        "typeAnnotation": {
+          "type": "TSConditionalType",
+          "start": 18,
+          "end": 47,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 18
+            },
+            "end": {
+              "line": 1,
+              "column": 47
+            }
+          },
+          "checkType": {
+            "type": "TSTypeReference",
+            "start": 18,
+            "end": 19,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 18
+              },
+              "end": {
+                "line": 1,
+                "column": 19
+              }
+            },
+            "typeName": {
+              "type": "Identifier",
+              "start": 18,
+              "end": 19,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 18
+                },
+                "end": {
+                  "line": 1,
+                  "column": 19
+                },
+                "identifierName": "T"
+              },
+              "name": "T"
+            }
+          },
+          "extendsType": {
+            "type": "TSArrayType",
+            "start": 28,
+            "end": 39,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 28
+              },
+              "end": {
+                "line": 1,
+                "column": 39
+              }
+            },
+            "elementType": {
+              "type": "TSParenthesizedType",
+              "start": 28,
+              "end": 37,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 28
+                },
+                "end": {
+                  "line": 1,
+                  "column": 37
+                }
+              },
+              "typeAnnotation": {
+                "type": "TSInferType",
+                "start": 29,
+                "end": 36,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 29
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 36
+                  }
+                },
+                "typeParameter": {
+                  "type": "TypeParameter",
+                  "start": 35,
+                  "end": 36,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 35
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 36
+                    }
+                  },
+                  "name": "U"
+                }
+              }
+            }
+          },
+          "trueType": {
+            "type": "TSTypeReference",
+            "start": 42,
+            "end": 43,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 42
+              },
+              "end": {
+                "line": 1,
+                "column": 43
+              }
+            },
+            "typeName": {
+              "type": "Identifier",
+              "start": 42,
+              "end": 43,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 42
+                },
+                "end": {
+                  "line": 1,
+                  "column": 43
+                },
+                "identifierName": "U"
+              },
+              "name": "U"
+            }
+          },
+          "falseType": {
+            "type": "TSTypeReference",
+            "start": 46,
+            "end": 47,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 46
+              },
+              "end": {
+                "line": 1,
+                "column": 47
+              }
+            },
+            "typeName": {
+              "type": "Identifier",
+              "start": 46,
+              "end": 47,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 46
+                },
+                "end": {
+                  "line": 1,
+                  "column": 47
+                },
+                "identifierName": "T"
+              },
+              "name": "T"
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babylon/test/fixtures/typescript/types/conditional/input.js

@@ -0,0 +1 @@
+let x: number extends string ? boolean : null;

packages/babylon/test/fixtures/typescript/types/conditional/output.json

@@ -0,0 +1,175 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 46,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 46
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 46,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 46
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "VariableDeclaration",
+        "start": 0,
+        "end": 46,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 46
+          }
+        },
+        "declarations": [
+          {
+            "type": "VariableDeclarator",
+            "start": 4,
+            "end": 45,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 4
+              },
+              "end": {
+                "line": 1,
+                "column": 45
+              }
+            },
+            "id": {
+              "type": "Identifier",
+              "start": 4,
+              "end": 45,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 4
+                },
+                "end": {
+                  "line": 1,
+                  "column": 45
+                },
+                "identifierName": "x"
+              },
+              "name": "x",
+              "typeAnnotation": {
+                "type": "TSTypeAnnotation",
+                "start": 5,
+                "end": 45,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 5
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 45
+                  }
+                },
+                "typeAnnotation": {
+                  "type": "TSConditionalType",
+                  "start": 7,
+                  "end": 45,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 45
+                    }
+                  },
+                  "checkType": {
+                    "type": "TSNumberKeyword",
+                    "start": 7,
+                    "end": 13,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 7
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 13
+                      }
+                    }
+                  },
+                  "extendsType": {
+                    "type": "TSStringKeyword",
+                    "start": 22,
+                    "end": 28,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 22
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 28
+                      }
+                    }
+                  },
+                  "trueType": {
+                    "type": "TSBooleanKeyword",
+                    "start": 31,
+                    "end": 38,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 31
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 38
+                      }
+                    }
+                  },
+                  "falseType": {
+                    "type": "TSNullKeyword",
+                    "start": 41,
+                    "end": 45,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 41
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 45
+                      }
+                    }
+                  }
+                }
+              }
+            },
+            "init": null
+          }
+        ],
+        "kind": "let"
+      }
+    ],
+    "directives": []
+  }
+}