Optimization (inference match result): Test compiler interface in order to generate MatchResult

Author: hildjj

lib/compiler/passes/inference-match-result.js

@@ -59,6 +59,14 @@ function inferenceMatchResult(ast) {
           // 6 == 3! -- permutations count for all transitions from one match
           // state to another.
           // After 6 iterations the cycle with guarantee begins
+          // For example, an input of `start = [] start` will generate the
+          // sequence: 0 -> -1 -> -1 (then stop)
+          //
+          // A more complex grammar theoretically would generate the
+          // sequence: 0 -> 1 -> 0 -> -1 -> 0 -> 1 -> ... (then cycle)
+          // but there are no examples of such grammars yet (possible, they
+          // do not exist at all)
+
           // istanbul ignore next  This is canary test, shouldn't trigger in real life
           if (++count > 6) {
             throw new GrammarError(

test/types/peg.test-d.ts

@@ -308,6 +308,21 @@ describe("peg.d.ts", () => {
       "zero_or_more",
     ]);
   });
+
+  it("compiles", () => {
+    const ast = peggy.parser.parse("start = 'foo'", {
+      grammarSource: "it compiles",
+      reservedWords: peggy.RESERVED_WORDS.slice(),
+    });
+    expectType<peggy.ast.Grammar>(ast);
+    const parser = peggy.compiler.compile(
+      ast,
+      peggy.compiler.passes
+    );
+    expectType<peggy.Parser>(parser);
+    expectType<peggy.ast.MatchResult|undefined>(ast.rules[0].match);
+    expect(ast.rules[0].match).toBe(0);
+  });
 });
 
 describe("run tsd", () => {