Port babel-parser changes from 2021-03-15 to 2021-04-28 (#636)

Instructions: https://github.com/alangpierce/sucrase/wiki/Porting-changes-from-Babel's-parser

4b674ea031 v7.13.11
🚫 Release only.

beb7cf8b24 Sort error keys with ESLint (#13020)
🚫 Babel-internal change.

edb11baabf v7.13.12
🚫 Release only.

4f727139ec fix(ts): Allow parenthesized "assert and assign" (#12933)
🚫 Seems to work fine in Sucrase.

0067fd9e02 Disallow await before exponential (#12441)
🚫 Validation only.

2f8203f190 v7.13.13
🚫 Release only.

8efbac4a5d fix: the LHS in for-of loop should not start with let (#13049)
🚫 Validation only.

a647b9ea6b Convert `@babel/core` to TypeScript (#12929)
🚫 Babel-internal.

7fe3ebf4db fix: raise `SyntaxError` for unparenthesized assert and assign (#13099)
🚫 Validation only.

42e630e8a2 Allow trailing comma after rest parameter in TSDeclareFunction (#13101)
🚫 Seems to work fine in Sucrase.

e50f6f7eef v7.13.15
🚫 Release only.

368bf893fa [ts] raise `SyntaxError` for `declare` before getter/setter (#13143)
🚫 Validation only.

d94a8e50ed v7.13.16
🚫 Release only.

10f4d08efb refactor: avoid parsing logic on locations (#13200)
🚫 Refactor not relevant to Sucrase.

0ee98139a6 Introduce parser error codes (#13033)
🚫 Error handling not relevant to Sucrase.

eac0259ce2 Support TS 4.3 static index signature in classes (#13096)
✅ Ported and updated parser to mark all modifiers as type tokens.

f8aa32f767 Support parsing Flow's Indexed Access Types (#13053)
✅ Straightforward port.

bf14a106ad Support TS 4.3 `override` syntax in class (#13097)
✅ Ported non-validation parts and implemented the feature in the transformer as well.

2521c666f7 Add internal ESLint rule for consistent parser error messages (#13130)
🚫 Error messaging only.

7484b51e56 Support TS 4.3 `get`/`set` type members (#13089)
✅ Ported, though the implementation needed some changes to avoid depending on the AST.

c949660b34 babel-parser: Deep freeze for `makeErrorTemplates` (#13142)
🚫 Babel internal.

generator/generateReadWordTree.ts

@@ -66,6 +66,7 @@ const CONTEXTUAL_KEYWORDS = [
   "opaque",
   "private",
   "protected",
+  "override",
   "proto",
   "public",
   "readonly",

generator/generateTokenTypes.ts

@@ -164,6 +164,7 @@ const types = {
   _public: new KeywordTokenType("public"),
   _private: new KeywordTokenType("private"),
   _protected: new KeywordTokenType("protected"),
+  _override: new KeywordTokenType("override"),
   _as: new KeywordTokenType("as"),
   _enum: new KeywordTokenType("enum"),
   _type: new KeywordTokenType("type"),

src/parser/plugins/flow.ts

@@ -645,7 +645,13 @@ function flowParsePostfixType(): void {
   flowParsePrimaryType();
   while (!canInsertSemicolon() && match(tt.bracketL)) {
     expect(tt.bracketL);
-    expect(tt.bracketR);
+    if (eat(tt.bracketR)) {
+      // Array type
+    } else {
+      // Indexed access type
+      flowParseType();
+      expect(tt.bracketR);
+    }
   }
 }
 

src/parser/plugins/typescript.ts

@@ -32,11 +32,8 @@ import {
   baseParseMaybeDecoratorArguments,
   parseBlockBody,
   parseClass,
-  parseClassProperty,
-  parseClassPropertyName,
   parseFunction,
   parseFunctionParams,
-  parsePostMemberNameModifiers,
   parseStatement,
   parseVarStatement,
 } from "../traverser/statement";
@@ -96,6 +93,15 @@ function tsNextTokenCanFollowModifier(): boolean {
   }
 }
 
+export function tsParseModifiers(allowedModifiers: Array<ContextualKeyword>): void {
+  while (true) {
+    const modifier = tsParseModifier(allowedModifiers);
+    if (modifier === null) {
+      break;
+    }
+  }
+}
+
 /** Parses a modifier matching one the given modifier names. */
 export function tsParseModifier(
   allowedModifiers: Array<ContextualKeyword>,
@@ -125,6 +131,9 @@ export function tsParseModifier(
       case ContextualKeyword._protected:
         state.tokens[state.tokens.length - 1].type = tt._protected;
         break;
+      case ContextualKeyword._override:
+        state.tokens[state.tokens.length - 1].type = tt._override;
+        break;
       case ContextualKeyword._declare:
         state.tokens[state.tokens.length - 1].type = tt._declare;
         break;
@@ -307,6 +316,13 @@ function tsParseTypeMember(): void {
   if (found) {
     return;
   }
+  if (
+    (isContextual(ContextualKeyword._get) || isContextual(ContextualKeyword._set)) &&
+    tsNextTokenCanFollowModifier()
+  ) {
+    // This is a getter/setter on a type. The tsNextTokenCanFollowModifier
+    // function already called next() for us, so continue parsing the name.
+  }
   parsePropertyName(-1 /* Types don't need context IDs. */);
   tsParsePropertyOrMethodSignature(readonly);
 }
@@ -1279,44 +1295,28 @@ export function tsParseAccessModifier(): void {
   ]);
 }
 
-export function tsTryParseClassMemberWithIsStatic(
-  isStatic: boolean,
-  classContextId: number,
-): boolean {
-  let isAbstract = false;
-  let isReadonly = false;
-
-  while (true) {
-    const mod = tsParseModifier([
-      ContextualKeyword._abstract,
-      ContextualKeyword._readonly,
-      ContextualKeyword._declare,
-    ]);
-    if (mod == null) {
-      break;
-    }
-    if (mod === ContextualKeyword._readonly) {
-      isReadonly = true;
-    }
-    if (mod === ContextualKeyword._abstract) {
-      isAbstract = true;
-    }
-  }
+export function tsTryParseClassMemberWithIsStatic(isStatic: boolean): boolean {
+  const memberStartIndexAfterStatic = state.tokens.length;
+  tsParseModifiers([
+    ContextualKeyword._abstract,
+    ContextualKeyword._readonly,
+    ContextualKeyword._declare,
+    ContextualKeyword._static,
+    ContextualKeyword._override,
+  ]);
 
-  // We no longer check for public/private/etc, but tsTryParseIndexSignature should just return
-  // false in that case for valid code.
-  if (!isAbstract && !isStatic) {
-    const found = tsTryParseIndexSignature();
-    if (found) {
-      return true;
+  const modifiersEndIndex = state.tokens.length;
+  const found = tsTryParseIndexSignature();
+  if (found) {
+    // Index signatures are type declarations, so set the modifier tokens as
+    // type tokens. Most tokens could be assumed to be type tokens, but `static`
+    // is ambiguous unless we set it explicitly here.
+    const memberStartIndex = isStatic
+      ? memberStartIndexAfterStatic - 1
+      : memberStartIndexAfterStatic;
+    for (let i = memberStartIndex; i < modifiersEndIndex; i++) {
+      state.tokens[i].isType = true;
     }
-  }
-
-  if (isReadonly) {
-    // Must be a property (if not an index signature).
-    parseClassPropertyName(classContextId);
-    parsePostMemberNameModifiers();
-    parseClassProperty();
     return true;
   }
   return false;

src/parser/tokenizer/keywords.ts

@@ -23,6 +23,7 @@ export enum ContextualKeyword {
   _namespace,
   _of,
   _opaque,
+  _override,
   _private,
   _protected,
   _proto,