Parse TypeScript syntax

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Parser and variable analyzer:

• interfaces
• classes
• type annotations on variable declarations
• <type>variable type assertions
• abstract methods
• as type assertions
• ! postfix operator
• type expression syntax
• generic parameters
• generic arguments
• decorators (Parse JS/TS decorators #964)
• enums
• import type
• export interface, export type, etc.
• namespaces
• declare
• module
• type aliases
• this parameters
• type predicates
• predeclared global types (e.g. Generator)
• type T<U>=number; (>=) TypeScript: parse let x:T<U>=y #848
• export abstract class
• satisfies
• infer (e.g. extends infer T extends syntax fail to compile evanw/esbuild#2712)
• false-positive(typescript): cannot use extends in generic parameter definition #919
• false-positive(typescript): cannot set default generic parameter value in function definition #921
• generic in/out
• constructor(public foo: number), constructor(public readonly foo: number)
• function f<const T>() {}
• TODOs (e.g. Multiple crashes when checking broken files #974, bug(false-positive): quick-lint does not allow a type and variable to have the same name #981)
• public declare readonly myField: number;
• export declare function ...
• <Type<GenericArg> /> (JSX + generic arguments)
• .d.ts syntax
• error on merged class/interface with mixed exportness (sorta) #1107
• let foo!: Bar;

Integrations:

• CLI: .ts, .tsx, .d.ts
• CLI: --language=typescript option
• LSP
• VS Code extension
• Vim plugins
• Emacs plugins
  • Flymake
  • Flycheck 8$: enable TypeScript for Flycheck Emacs plugin #1148
  • Eglot 10$: enable TypeScript for Eglot Emacs plugin #1146
  • lsp-mode 10$: enable TypeScript for LSP Mode Emacs plugin #1147
• Sublime Text plugin
• Kate plugin 10$: enable TypeScript for Kate plugin #1149
• web demo
• Experimental:
  • CLI: --language=experimental-typescript option
  • CLI: .ts, .tsx, .d.ts (--language=experimental-default option)
  • LSP
  • Emacs plugins
  • VS Code extension
  • Vim plugins

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TypeScript keywords: https://github.com/microsoft/TypeScript/blob/99ffa394a838a5528d6118fb3c23f81fd8e99ab2/src/compiler/scanner.ts#L81

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Interfaces

• interfaces are typechecking-only and cannot be used in expressions.
• functions, const/let/var/catch variables, and parameters are runtime-only and cannot be used in types.
• classes are usable both in expressions and in types.
• imported variables are usable according to the above rules. Without looking at the imported module, there is no way to know if an imported variable can be used in an expression or in a type.

Conflicts:

• If an interface and a function/variable have the same name, there is no ambiguity.
• If an interface has the same name as an imported class or interface, there is a compile error.
• If an interface has the same name as an imported function/const/let/var, there is no compile error.
• If an interface and a class have the same name, then the declarations seem to be merged (union of all members). This can lead to violations in the type system. For example:

interface I { field: number }
class I { }
let o = new I(); // not a type error
console.log(o.field.toString()); // run-time error!

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Some interesting syntax quirks related to JSX:
https://github.com/rome/tools/blob/f68757316355bb931c0420a686082297978a370e/crates/rome_js_parser/test_data/inline/err/jsx_or_type_assertion.js
https://stackoverflow.com/a/54614279/39992

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Here's an interesting file we could use for performance testing (almost 7 MiB): https://raw.githubusercontent.com/NativeScript/NativeScript/main/packages/types-android/src/lib/android/android-platform-31.d.ts

and another (over 2 MiB): https://github.com/microsoft/TypeScript/blob/main/src/compiler/checker.ts

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TypeScript has too many syntax-level features. @_@

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TypeScript has too many syntax-level features. @_@

you're tellin' me!

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Shipped in version 3.0.0.