fix #1512: asi issue with "." and type parameters

CHANGELOG.md

@@ -25,6 +25,19 @@
 
     This mirrors how the JS code generator similarly avoids the character sequence `</script`.
 
+* Fix a TypeScript parsing edge case with ASI (Automatic Semicolon Insertion) ([#1512](https://github.com/evanw/esbuild/issues/1512))
+
+    This fixes a parsing bug where TypeScript types consisting of multiple identifiers joined together with a `.` could incorrectly extend onto the next line if the next line started with `<`. This problem was due to ASI; esbuild should be automatically inserting a semicolon at the end of the line:
+
+    ```ts
+    let x: {
+      <A extends B>(): c.d
+      <E extends F>(): g.h
+    }
+    ```
+
+    Previously the above code was a syntax error. With this release, this code is now parsed correctly.
+
 ## 0.12.19
 
 * Add support for CSS source maps ([#519](https://github.com/evanw/esbuild/issues/519))

internal/js_parser/ts_parser.go

@@ -388,7 +388,11 @@ func (p *parser) skipTypeScriptTypeWithOpts(level js_ast.L, opts skipTypeOpts) {
 				p.lexer.Expect(js_lexer.TIdentifier)
 			}
 			p.lexer.Next()
-			p.skipTypeScriptTypeArguments(false /* isInsideJSXElement */)
+
+			// "{ <A extends B>(): c.d \n <E extends F>(): g.h }" must not become a single type
+			if !p.lexer.HasNewlineBefore {
+				p.skipTypeScriptTypeArguments(false /* isInsideJSXElement */)
+			}
 
 		case js_lexer.TOpenBracket:
 			// "{ ['x']: string \n ['y']: string }" must not become a single type

internal/js_parser/ts_parser_test.go

@@ -115,6 +115,12 @@ func TestTSTypes(t *testing.T) {
 	expectParseErrorTS(t, "let x: typeof readonly Array", "<stdin>: error: Expected \";\" but found \"Array\"\n")
 	expectPrintedTS(t, "let x: `y`", "let x;\n")
 	expectParseErrorTS(t, "let x: tag`y`", "<stdin>: error: Expected \";\" but found \"`y`\"\n")
+	expectPrintedTS(t, "let x: { <A extends B>(): c.d \n <E extends F>(): g.h }", "let x;\n")
+	expectPrintedTSX(t, "type x = a.b \n <c></c>", "/* @__PURE__ */ React.createElement(\"c\", null);\n")
+	expectPrintedTS(t, "type Foo = a.b \n | c.d", "")
+	expectPrintedTS(t, "type Foo = a.b \n & c.d", "")
+	expectPrintedTS(t, "type Foo = \n | a.b \n | c.d", "")
+	expectPrintedTS(t, "type Foo = \n & a.b \n & c.d", "")
 
 	expectPrintedTS(t, "let x: A.B<X.Y>", "let x;\n")
 	expectPrintedTS(t, "let x: A.B<X.Y>=2", "let x = 2;\n")