Implement Smart Pipeline proposal in @babel/parser

packages/babel-parser/src/tokenizer/index.js

@@ -404,6 +404,43 @@ export default class Tokenizer extends LocationParser {
   //
   // All in the name of speed.
   //
+  readToken_numberSign(code: number): void {
+    if (this.state.pos === 0 && this.readToken_interpreter()) {
+      return;
+    }
+
+    const nextPos = this.state.pos + 1;
+    const next = this.input.charCodeAt(nextPos);
+    // if (isIdentifierStart(next)) {
+    if (
+      (this.hasPlugin("classPrivateProperties") ||
+        this.hasPlugin("classPrivateMethods")) &&
+      this.state.classLevel > 0
+    ) {
+      ++this.state.pos;
+      this.finishToken(tt.hash);
+      return;
+    } else if (
+      "smart" === this.getPluginOption("pipelineOperator", "proposal")
+    ) {
+      if (next >= charCodes.digit0 && next <= charCodes.digit9) {
+        this.raise(
+          this.state.pos,
+          `Unexpected digit after topic reference: '#${String.fromCodePoint(
+            next,
+          )}'`,
+        );
+      } else {
+        this.finishOp(tt.primaryTopicReference, 1);
+      }
+    } else {
+      this.raise(
+        this.state.pos,
+        `Unexpected character '${codePointToString(code)}'`,
+      );
+    }
+  }
+
   readToken_dot(): void {
     const next = this.input.charCodeAt(this.state.pos + 1);
     if (next >= charCodes.digit0 && next <= charCodes.digit9) {
@@ -651,25 +688,12 @@ export default class Tokenizer extends LocationParser {
 
   getTokenFromCode(code: number): void {
     switch (code) {
-      case charCodes.numberSign:
-        if (this.state.pos === 0 && this.readToken_interpreter()) {
-          return;
-        }
+      // The interpretation of a number sign "#" depends on whether it is
+      // followed by an identifier or not.
 
-        if (
-          (this.hasPlugin("classPrivateProperties") ||
-            this.hasPlugin("classPrivateMethods")) &&
-          this.state.classLevel > 0
-        ) {
-          ++this.state.pos;
-          this.finishToken(tt.hash);
-          return;
-        } else {
-          this.raise(
-            this.state.pos,
-            `Unexpected character '${codePointToString(code)}'`,
-          );
-        }
+      case charCodes.numberSign:
+        this.readToken_numberSign(code);
+        return;
 
       // The interpretation of a dot depends on whether it is followed
       // by a digit or another two dots.

packages/babel-parser/src/tokenizer/state.js

@@ -33,6 +33,12 @@ export default class State {
     this.hasFlowComment = false;
     this.isIterator = false;
 
+    // Used by smartPipelines.
+    this.topicContextState = {
+      maxNumOfResolvableTopics: 0,
+      maxTopicIndex: undefined,
+    };
+
     this.classLevel = 0;
 
     this.labels = [];
@@ -111,6 +117,9 @@ export default class State {
   hasFlowComment: boolean;
   isIterator: boolean;
 
+  // For the smartPipelines plugin:
+  topicContextState: tt.TopicContextState;
+
   // Check whether we are in a (nested) class or not.
   classLevel: number;
 

packages/babel-parser/src/tokenizer/types.js

@@ -86,6 +86,7 @@ export const types: { [name: string]: TokenType } = {
   regexp: new TokenType("regexp", { startsExpr }),
   string: new TokenType("string", { startsExpr }),
   name: new TokenType("name", { startsExpr }),
+  primaryTopicReference: new TokenType("#", { startsExpr }),
   eof: new TokenType("eof"),
 
   // Punctuation token types.
@@ -199,3 +200,17 @@ export const keywords = {
 Object.keys(keywords).forEach(name => {
   types["_" + name] = keywords[name];
 });
+
+// A type for the smartPipelines plugin.
+export type TopicContextState = {
+  // When a topic binding has been currently established,
+  // then this is 1. Otherwise, it is 0. This is forwards compatible
+  // with a future plugin for multiple lexical topics.
+  maxNumOfResolvableTopics: number,
+
+  // When a topic binding has been currently established, and if that binding
+  // has been used as a topic reference `#`, then this is 0. Otherwise, it is
+  // `null`. This is forwards compatible with a future plugin for multiple
+  // lexical topics.
+  maxTopicIndex: null | 0,
+};