fix(es/parser): Rescan << as < when parsing type args (#8607)

**Description:** The related issue is a product to the fact that the lexer sees a `<<` token in `fun<<T>...` and therefore parses the type args as an arrow function. This PR adds the handling of the "split" of `<<` when beginning to parse type args. I am open for suggestions, I still find this a bit odd (in `parse_ts_type_args()`): ```rs if is!(p, "<<") { p.input.cut_lshift(); } else { expect!(p, '<'); } ``` **Related issue:** - Closes #7187 - Closes #8209 - Closes #8581
swc-project · Feb 6, 2024 · 9e6dad9 · 9e6dad9
1 parent c3f67ce
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diff --git a/crates/swc/tests/fixture/issues-7xxx/7187/input/.swcrc b/crates/swc/tests/fixture/issues-7xxx/7187/input/.swcrc
@@ -0,0 +1,22 @@
+{
+  "jsc": {
+    "parser": {
+      "syntax": "typescript",
+      "tsx": true
+    },
+    "target": "es2022",
+    "transform": {
+      "useDefineForClassFields": true,
+      "react": {
+        "importSource": "https://esm.sh/preact",
+        "runtime": "automatic"
+      }
+    },
+    "loose": false
+  },
+  "module": {
+    "type": "es6"
+  },
+  "minify": false,
+  "isModule": true
+}
diff --git a/crates/swc/tests/fixture/issues-7xxx/7187/input/index.ts b/crates/swc/tests/fixture/issues-7xxx/7187/input/index.ts
@@ -0,0 +1 @@
+assertType<<K>(key: K) => K>(foo);
diff --git a/crates/swc/tests/fixture/issues-7xxx/7187/output/index.ts b/crates/swc/tests/fixture/issues-7xxx/7187/output/index.ts
@@ -0,0 +1 @@
+assertType(foo);
diff --git a/crates/swc/tests/fixture/issues-8xxx/8209/input/.swcrc b/crates/swc/tests/fixture/issues-8xxx/8209/input/.swcrc
@@ -0,0 +1,28 @@
+{
+  "jsc": {
+    "parser": {
+      "syntax": "typescript",
+      "tsx": true
+    },
+    "target": "es2022",
+    "transform": {
+      "optimizer": {
+        "globals": {
+          "vars": {
+            "__NODE__": "true"
+          }
+        },
+      },
+    },
+    "loose": false,
+    "minify": {
+      "compress": false,
+      "mangle": false
+    }
+  },
+  "module": {
+    "type": "es6"
+  },
+  "minify": false,
+  "isModule": true
+}
diff --git a/crates/swc/tests/fixture/issues-8xxx/8209/input/input.ts b/crates/swc/tests/fixture/issues-8xxx/8209/input/input.ts
@@ -0,0 +1,3 @@
+const Context = createContext<<Key extends keyof Config>(key: Key) => Config[Key]>(
+    (key) => properties[key]?.default
+);
diff --git a/crates/swc/tests/fixture/issues-8xxx/8209/output/input.ts b/crates/swc/tests/fixture/issues-8xxx/8209/output/input.ts
@@ -0,0 +1 @@
+const Context = createContext((key)=>properties[key]?.default);
diff --git a/crates/swc_ecma_parser/src/macros.rs b/crates/swc_ecma_parser/src/macros.rs
@@ -110,6 +110,9 @@ macro_rules! tok {
     ('<') => {
         crate::token::Token::BinOp(crate::token::BinOpToken::Lt)
     };
+    ("<<") => {
+        crate::token::Token::BinOp(crate::token::BinOpToken::LShift)
+    };
     ('>') => {
         crate::token::Token::BinOp(crate::token::BinOpToken::Gt)
     };

diff --git a/crates/swc_ecma_parser/src/parser/expr.rs b/crates/swc_ecma_parser/src/parser/expr.rs
@@ -1596,7 +1596,7 @@ impl<I: Tokens> Parser<I> {
         let callee = self.parse_new_expr()?;
         return_if_arrow!(self, callee);
 
-        let type_args = if self.input.syntax().typescript() && is!(self, '<') {
+        let type_args = if self.input.syntax().typescript() && is_one_of!(self, '<', "<<") {
             self.try_parse_ts(|p| {
                 let type_args = p.parse_ts_type_args()?;
                 if is!(p, '(') {

diff --git a/crates/swc_ecma_parser/src/parser/input.rs b/crates/swc_ecma_parser/src/parser/input.rs
@@ -383,6 +383,19 @@ impl<I: Tokens> Buffer<I> {
         }
     }
 
+    #[inline]
+    pub fn cut_lshift(&mut self) {
+        debug_assert!(
+            self.is(&tok!("<<")),
+            "parser should only call cut_lshift when encountering LShift token"
+        );
+        self.cur = Some(TokenAndSpan {
+            token: tok!('<'),
+            span: self.cur_span().with_lo(self.cur_span().lo + BytePos(1)),
+            had_line_break: false,
+        });
+    }
+
     #[inline]
     pub fn is(&mut self, expected: &Token) -> bool {
         match self.cur() {

diff --git a/crates/swc_ecma_parser/src/parser/typescript.rs b/crates/swc_ecma_parser/src/parser/typescript.rs
@@ -2666,7 +2666,11 @@ impl<I: Tokens> Parser<I> {
             // Temporarily remove a JSX parsing context, which makes us scan different
             // tokens.
             p.ts_in_no_context(|p| {
-                expect!(p, '<');
+                if is!(p, "<<") {
+                    p.input.cut_lshift();
+                } else {
+                    expect!(p, '<');
+                }
                 p.parse_ts_delimited_list(ParsingContext::TypeParametersOrArguments, |p| {
                     trace_cur!(p, parse_ts_type_args__arg);
 

diff --git a/crates/swc_ecma_parser/tests/typescript/issue-7187/input.ts b/crates/swc_ecma_parser/tests/typescript/issue-7187/input.ts
@@ -0,0 +1 @@
+assertType<<K>(key: K) => K>(foo);
diff --git a/crates/swc_ecma_parser/tests/typescript/issue-7187/input.ts.json b/crates/swc_ecma_parser/tests/typescript/issue-7187/input.ts.json
@@ -0,0 +1,169 @@
+{
+  "type": "Script",
+  "span": {
+    "start": 1,
+    "end": 35,
+    "ctxt": 0
+  },
+  "body": [
+    {
+      "type": "ExpressionStatement",
+      "span": {
+        "start": 1,
+        "end": 35,
+        "ctxt": 0
+      },
+      "expression": {
+        "type": "CallExpression",
+        "span": {
+          "start": 1,
+          "end": 34,
+          "ctxt": 0
+        },
+        "callee": {
+          "type": "Identifier",
+          "span": {
+            "start": 1,
+            "end": 11,
+            "ctxt": 0
+          },
+          "value": "assertType",
+          "optional": false
+        },
+        "arguments": [
+          {
+            "spread": null,
+            "expression": {
+              "type": "Identifier",
+              "span": {
+                "start": 30,
+                "end": 33,
+                "ctxt": 0
+              },
+              "value": "foo",
+              "optional": false
+            }
+          }
+        ],
+        "typeArguments": {
+          "type": "TsTypeParameterInstantiation",
+          "span": {
+            "start": 11,
+            "end": 29,
+            "ctxt": 0
+          },
+          "params": [
+            {
+              "type": "TsFunctionType",
+              "span": {
+                "start": 12,
+                "end": 28,
+                "ctxt": 0
+              },
+              "params": [
+                {
+                  "type": "Identifier",
+                  "span": {
+                    "start": 16,
+                    "end": 22,
+                    "ctxt": 0
+                  },
+                  "value": "key",
+                  "optional": false,
+                  "typeAnnotation": {
+                    "type": "TsTypeAnnotation",
+                    "span": {
+                      "start": 19,
+                      "end": 22,
+                      "ctxt": 0
+                    },
+                    "typeAnnotation": {
+                      "type": "TsTypeReference",
+                      "span": {
+                        "start": 21,
+                        "end": 22,
+                        "ctxt": 0
+                      },
+                      "typeName": {
+                        "type": "Identifier",
+                        "span": {
+                          "start": 21,
+                          "end": 22,
+                          "ctxt": 0
+                        },
+                        "value": "K",
+                        "optional": false
+                      },
+                      "typeParams": null
+                    }
+                  }
+                }
+              ],
+              "typeParams": {
+                "type": "TsTypeParameterDeclaration",
+                "span": {
+                  "start": 12,
+                  "end": 15,
+                  "ctxt": 0
+                },
+                "parameters": [
+                  {
+                    "type": "TsTypeParameter",
+                    "span": {
+                      "start": 13,
+                      "end": 14,
+                      "ctxt": 0
+                    },
+                    "name": {
+                      "type": "Identifier",
+                      "span": {
+                        "start": 13,
+                        "end": 14,
+                        "ctxt": 0
+                      },
+                      "value": "K",
+                      "optional": false
+                    },
+                    "in": false,
+                    "out": false,
+                    "const": false,
+                    "constraint": null,
+                    "default": null
+                  }
+                ]
+              },
+              "typeAnnotation": {
+                "type": "TsTypeAnnotation",
+                "span": {
+                  "start": 24,
+                  "end": 28,
+                  "ctxt": 0
+                },
+                "typeAnnotation": {
+                  "type": "TsTypeReference",
+                  "span": {
+                    "start": 27,
+                    "end": 28,
+                    "ctxt": 0
+                  },
+                  "typeName": {
+                    "type": "Identifier",
+                    "span": {
+                      "start": 27,
+                      "end": 28,
+                      "ctxt": 0
+                    },
+                    "value": "K",
+                    "optional": false
+                  },
+                  "typeParams": null
+                }
+              }
+            }
+          ]
+        }
+      }
+    }
+  ],
+  "interpreter": null
+}
diff --git a/crates/swc_ecma_parser/tests/typescript/issue-8209/input.ts b/crates/swc_ecma_parser/tests/typescript/issue-8209/input.ts
@@ -0,0 +1,3 @@
+const Context = createContext<<Key extends keyof Config>(key: Key) => Config[Key]>(
+    (key) => properties[key]?.default
+);