feat(es/parser): Add an option to disallow ambiguous jsx (#6913)

crates/swc/src/config/mod.rs

@@ -775,6 +775,7 @@ impl Default for Rc {
                 jsc: JscConfig {
                     syntax: Some(Syntax::Typescript(TsConfig {
                         tsx: false,
+                        disallow_ambiguous_jsx_like: true,
                         ..Default::default()
                     })),
                     ..Default::default()

crates/swc/tests/rust_api.rs

@@ -136,6 +136,7 @@ fn shopify_2_same_opt() {
                         decorators: false,
                         dts: false,
                         no_early_errors: false,
+                        disallow_ambiguous_jsx_like: false,
                     })),
                     transform: None.into(),
                     external_helpers: false.into(),

crates/swc/tests/tsc.rs

@@ -380,6 +380,7 @@ fn matrix(input: &Path) -> Vec<TestUnitData> {
                                 decorators,
                                 dts: false,
                                 no_early_errors: false,
+                                disallow_ambiguous_jsx_like: false,
                             })),
                             external_helpers: true.into(),
                             target: Some(target),

crates/swc_ecma_dep_graph/src/lib.rs

@@ -399,6 +399,7 @@ mod tests {
                     tsx: file_name.contains("tsx"),
                     decorators: true,
                     no_early_errors: true,
+                    disallow_ambiguous_jsx_like: false,
                 }),
                 EsVersion::Es2015,
                 (&*fm).into(),

crates/swc_ecma_parser/src/error.rs

@@ -278,6 +278,9 @@ pub enum SyntaxError {
         span: Span,
         note: &'static str,
     },
+
+    ReservedTypeAssertion,
+    ReservedArrowTypeParam,
 }
 
 impl SyntaxError {
@@ -709,6 +712,14 @@ impl SyntaxError {
                 format!("Unexpected token. Did you mean {}?", did_you_mean).into()
             }
             SyntaxError::WithLabel { inner, .. } => inner.error.1.msg(),
+            SyntaxError::ReservedTypeAssertion => "This syntax is reserved in files with the .mts \
+                                                   or .cts extension. Use an `as` expression \
+                                                   instead."
+                .into(),
+            SyntaxError::ReservedArrowTypeParam => "This syntax is reserved in files with the \
+                                                    .mts or .cts extension. Add a trailing comma, \
+                                                    as in `<T,>() => ...`."
+                .into(),
         }
     }
 }

crates/swc_ecma_parser/src/lib.rs

@@ -275,6 +275,13 @@ impl Syntax {
             Syntax::Es(..) => true,
         }
     }
+
+    fn disallow_ambiguous_jsx_like(self) -> bool {
+        match self {
+            Syntax::Typescript(t) => t.disallow_ambiguous_jsx_like,
+            _ => false,
+        }
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Deserialize)]
@@ -292,6 +299,14 @@ pub struct TsConfig {
 
     #[serde(skip, default)]
     pub no_early_errors: bool,
+
+    /// babel: `disallowAmbiguousJSXLike`
+    /// Even when JSX parsing is not enabled, this option disallows using syntax
+    /// that would be ambiguous with JSX (`<X> y` type assertions and
+    /// `<X>()=>{}` type arguments)
+    /// see: https://babeljs.io/docs/en/babel-plugin-transform-typescript#disallowambiguousjsxlike
+    #[serde(skip, default)]
+    pub disallow_ambiguous_jsx_like: bool,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Deserialize)]

crates/swc_ecma_parser/src/parser/expr.rs

@@ -82,6 +82,7 @@ impl<I: Tokens> Parser<I> {
     #[cfg_attr(feature = "debug", tracing::instrument(skip_all))]
     fn parse_assignment_expr_base(&mut self) -> PResult<Box<Expr>> {
         trace_cur!(self, parse_assignment_expr_base);
+        let start = self.input.cur_span();
 
         if self.input.syntax().typescript()
             && (is_one_of!(self, '<', JSXTagStart))
@@ -120,6 +121,9 @@ impl<I: Tokens> Parser<I> {
                 Ok(Some(arrow))
             });
             if let Some(res) = res {
+                if self.input.syntax().disallow_ambiguous_jsx_like() {
+                    self.emit_err(start, SyntaxError::ReservedArrowTypeParam);
+                }
                 return Ok(res);
             }
         }

crates/swc_ecma_parser/src/parser/typescript.rs

@@ -994,6 +994,10 @@ impl<I: Tokens> Parser<I> {
     pub(super) fn parse_ts_type_assertion(&mut self, start: BytePos) -> PResult<TsTypeAssertion> {
         debug_assert!(self.input.syntax().typescript());
 
+        if self.input.syntax().disallow_ambiguous_jsx_like() {
+            self.emit_err(span!(self, start), SyntaxError::ReservedTypeAssertion);
+        }
+
         // Not actually necessary to set state.inType because we never reach here if JSX
         // plugin is enabled, but need `tsInType` to satisfy the assertion in
         // `tsParseType`.

crates/swc_ecma_parser/tests/typescript-errors/disallow-ambiguous-jsx-like/cts-case1/input.cts

@@ -0,0 +1 @@
+<T>x;

crates/swc_ecma_parser/tests/typescript-errors/disallow-ambiguous-jsx-like/cts-case1/input.cts.swc-stderr

@@ -0,0 +1,6 @@
+
+  x This syntax is reserved in files with the .mts or .cts extension. Use an `as` expression instead.
+   ,-[$DIR/tests/typescript-errors/disallow-ambiguous-jsx-like/cts-case1/input.cts:1:1]
+ 1 | <T>x;
+   : ^
+   `----

crates/swc_ecma_parser/tests/typescript-errors/disallow-ambiguous-jsx-like/cts-case2/input.cts

@@ -0,0 +1 @@
+<T>() => 1;

crates/swc_ecma_parser/tests/typescript-errors/disallow-ambiguous-jsx-like/cts-case2/input.cts.swc-stderr

@@ -0,0 +1,6 @@
+
+  x This syntax is reserved in files with the .mts or .cts extension. Add a trailing comma, as in `<T,>() => ...`.
+   ,-[$DIR/tests/typescript-errors/disallow-ambiguous-jsx-like/cts-case2/input.cts:1:1]
+ 1 | <T>() => 1;
+   : ^
+   `----

crates/swc_ecma_parser/tests/typescript-errors/disallow-ambiguous-jsx-like/mts-case1/input.mts

@@ -0,0 +1 @@
+<T>x;

crates/swc_ecma_parser/tests/typescript-errors/disallow-ambiguous-jsx-like/mts-case1/input.mts.swc-stderr

@@ -0,0 +1,6 @@
+
+  x This syntax is reserved in files with the .mts or .cts extension. Use an `as` expression instead.
+   ,-[$DIR/tests/typescript-errors/disallow-ambiguous-jsx-like/mts-case1/input.mts:1:1]
+ 1 | <T>x;
+   : ^
+   `----

crates/swc_ecma_parser/tests/typescript-errors/disallow-ambiguous-jsx-like/mts-case2/input.mts

@@ -0,0 +1 @@
+<T>(x) => 1;

crates/swc_ecma_parser/tests/typescript-errors/disallow-ambiguous-jsx-like/mts-case2/input.mts.swc-stderr

@@ -0,0 +1,6 @@
+
+  x This syntax is reserved in files with the .mts or .cts extension. Add a trailing comma, as in `<T,>() => ...`.
+   ,-[$DIR/tests/typescript-errors/disallow-ambiguous-jsx-like/mts-case2/input.mts:1:1]
+ 1 | <T>(x) => 1;
+   : ^
+   `----

crates/swc_ecma_parser/tests/typescript.rs

@@ -242,6 +242,7 @@ where
                 tsx: fname.contains("tsx"),
                 decorators: true,
                 no_early_errors,
+                disallow_ambiguous_jsx_like: fname.contains("cts") || fname.contains("mts"),
                 ..Default::default()
             }),
             EsVersion::Es2015,
@@ -266,6 +267,8 @@ where
 }
 
 #[testing::fixture("tests/typescript-errors/**/*.ts")]
+#[testing::fixture("tests/typescript-errors/**/*.mts")]
+#[testing::fixture("tests/typescript-errors/**/*.cts")]
 #[testing::fixture("tests/typescript-errors/**/*.tsx")]
 fn errors(file: PathBuf) {
     let file_name = file.display().to_string();

crates/swc_ecma_parser/tests/typescript/disallow-ambiguous-jsx-like/cts/input.cts

@@ -0,0 +1,2 @@
+<T,>() => 1;
+<T,>(x) => 1;

crates/swc_ecma_parser/tests/typescript/disallow-ambiguous-jsx-like/cts/input.cts.json

@@ -0,0 +1,149 @@
+{
+  "type": "Script",
+  "span": {
+    "start": 1,
+    "end": 27,
+    "ctxt": 0
+  },
+  "body": [
+    {
+      "type": "ExpressionStatement",
+      "span": {
+        "start": 1,
+        "end": 13,
+        "ctxt": 0
+      },
+      "expression": {
+        "type": "ArrowFunctionExpression",
+        "span": {
+          "start": 1,
+          "end": 12,
+          "ctxt": 0
+        },
+        "params": [],
+        "body": {
+          "type": "NumericLiteral",
+          "span": {
+            "start": 11,
+            "end": 12,
+            "ctxt": 0
+          },
+          "value": 1.0,
+          "raw": "1"
+        },
+        "async": false,
+        "generator": false,
+        "typeParameters": {
+          "type": "TsTypeParameterDeclaration",
+          "span": {
+            "start": 1,
+            "end": 5,
+            "ctxt": 0
+          },
+          "parameters": [
+            {
+              "type": "TsTypeParameter",
+              "span": {
+                "start": 2,
+                "end": 3,
+                "ctxt": 0
+              },
+              "name": {
+                "type": "Identifier",
+                "span": {
+                  "start": 2,
+                  "end": 3,
+                  "ctxt": 0
+                },
+                "value": "T",
+                "optional": false
+              },
+              "in": false,
+              "out": false,
+              "const": false,
+              "constraint": null,
+              "default": null
+            }
+          ]
+        },
+        "returnType": null
+      }
+    },
+    {
+      "type": "ExpressionStatement",
+      "span": {
+        "start": 14,
+        "end": 27,
+        "ctxt": 0
+      },
+      "expression": {
+        "type": "ArrowFunctionExpression",
+        "span": {
+          "start": 14,
+          "end": 26,
+          "ctxt": 0
+        },
+        "params": [
+          {
+            "type": "Identifier",
+            "span": {
+              "start": 19,
+              "end": 20,
+              "ctxt": 0
+            },
+            "value": "x",
+            "optional": false,
+            "typeAnnotation": null
+          }
+        ],
+        "body": {
+          "type": "NumericLiteral",
+          "span": {
+            "start": 25,
+            "end": 26,
+            "ctxt": 0
+          },
+          "value": 1.0,
+          "raw": "1"
+        },
+        "async": false,
+        "generator": false,
+        "typeParameters": {
+          "type": "TsTypeParameterDeclaration",
+          "span": {
+            "start": 14,
+            "end": 18,
+            "ctxt": 0
+          },
+          "parameters": [
+            {
+              "type": "TsTypeParameter",
+              "span": {
+                "start": 15,
+                "end": 16,
+                "ctxt": 0
+              },
+              "name": {
+                "type": "Identifier",
+                "span": {
+                  "start": 15,
+                  "end": 16,
+                  "ctxt": 0
+                },
+                "value": "T",
+                "optional": false
+              },
+              "in": false,
+              "out": false,
+              "const": false,
+              "constraint": null,
+              "default": null
+            }
+          ]
+        },
+        "returnType": null
+      }
+    }
+  ],
+  "interpreter": null
+}

crates/swc_ecma_parser/tests/typescript/disallow-ambiguous-jsx-like/mts/input.mts

@@ -0,0 +1,2 @@
+<T,>() => 1;
+<T,>(x) => 1;