Add SyntaxErrorConstructor type, fixes #216

CHANGELOG.md

@@ -31,6 +31,7 @@ Released: TBD
 - [#169](https://github.com/peggyjs/peggy/issues/169): Expose string escape functions
 - [#197](https://github.com/peggyjs/peggy/pull/197): Fix a regression of redundant commas in the
   character classes in the error messages, introduced in fad4ab74d1de67ef1902cd22d479c81ccab73224
+- [#216](https://github.com/peggyjs/peggy/issues/216): Fix typescript definition of SyntaxError
 
 1.2.0
 -----

lib/peg.d.ts

@@ -421,6 +421,25 @@ export namespace parser {
     | EndExpectation
     | OtherExpectation;
 
+  interface SyntaxErrorConstructor {
+    new (
+      message: string,
+      expected: Expectation[] | null,
+      found: string | null,
+      location: LocationRange
+    ): SyntaxError;
+    readonly prototype: SyntaxError;
+
+    // Static methods
+    /**
+     * Constructs the human-readable message from the machine representation.
+     *
+     * @param expected Array of expected items, generated by the parser
+     * @param found Any text that will appear as found in the input instead of expected
+     */
+    buildMessage(expected: Expectation[], found: string): string;
+  }
+
   /** Thrown if the grammar contains a syntax error. */
   class SyntaxError extends Error {
     /** Location where error was originated. */
@@ -457,14 +476,6 @@ export namespace parser {
      * @returns the formatted error
      */
     format(sources: SourceText[]): string;
-
-    /**
-     * Constructs the human-readable message from the machine representation.
-     *
-     * @param expected Array of expected items, generated by the parser
-     * @param found Any text that will appear as found in the input instead of expected
-     */
-    static buildMessage(expected: Expectation[], found: string): string;
   }
 }
 
@@ -817,7 +828,7 @@ export interface ParserOptions {
 export interface Parser {
   parse(input: string, options?: ParserOptions): any;
 
-  SyntaxError: parser.SyntaxError;
+  SyntaxError: parser.SyntaxErrorConstructor;
 }
 
 export interface ParserTracer {

test/types/peg.test-d.ts

@@ -31,6 +31,19 @@ describe("peg.d.ts", () => {
     expect(res).toStrictEqual(["buzz", 11, "fizz"]);
   });
 
+  it("types SyntaxError correctly", () => {
+    const parser = peggy.generate(src);
+
+    expectType<peggy.parser.SyntaxErrorConstructor>(parser.SyntaxError);
+    expectType<peggy.parser.SyntaxError>(new parser.SyntaxError("", null, null, {
+      source: null,
+      start: { line: 0, column: 0, offset: 0 },
+      end: { line: 0, column: 0, offset: 0 },
+    }));
+
+    expectType<string>(parser.SyntaxError.buildMessage([], ""));
+  });
+
   it("takes a valid tracer", () => {
     const parser = peggy.generate(src, { trace: true });
     expectType<peggy.Parser>(parser);