Support definite assignment assertion x!: i32 (#260)

tests/parser/definite-assignment-assertion.ts

@@ -0,0 +1,9 @@
+class C {
+  x!: i32;
+  x!: i32 = 0;
+  static x!: i32;
+}
+function f(): void {
+  let x!: i32;
+  let x!: i32 = 0;
+}

tests/parser/definite-assignment-assertion.ts.fixture.ts

@@ -0,0 +1,12 @@
+class C {
+  x!: i32;
+  x!: i32 = 0;
+  static x!: i32;
+}
+function f(): void {
+  let x!: i32;
+  let x!: i32 = 0;
+}
+// ERROR 1255: "A definite assignment assertion '!' is not permitted in this context." in definite-assignment-assertion.ts:3:10
+// ERROR 1255: "A definite assignment assertion '!' is not permitted in this context." in definite-assignment-assertion.ts:4:14
+// ERROR 1255: "A definite assignment assertion '!' is not permitted in this context." in definite-assignment-assertion.ts:8:6

tests/parser/optional-property.ts

@@ -0,0 +1,3 @@
+class C {
+  x?: i32;
+}

tests/parser/optional-property.ts.fixture.ts

@@ -0,0 +1,4 @@
+class C {
+  x: i32;
+}
+// ERROR 219: "Optional properties are not supported." in optional-property.ts:2:9