CHANGELOG.md

0.24.1

2024-10-25

A bugfix release for Teal 0.24. Several fixes that bring the implementation closer to the vision of what the 2024 edition is intended to be, thanks to the invaluable feedback of the user community!

This release features commits by François Perrad, Steve Vermeulen and Hisham Muhammad.

What's New

Language

• Standard library
  • Improved signatures for math.frexp and math.ldexp

Fixes

As expected, fixes are mainly related to the new features introduced in Teal 0.24:

• Better handling of abstract vs. concrete types
  • Fixed subtyping and casting checks for records vs. interfaces (#830).
  • Disallow passing non-record types as arguments (#813).
  • Allow interface instances to be required concretely
  • Always elide abstract types from generated code
• Fixes for improved type inference
  • Fixed type inference for is x == nil or ... (#823).
  • Resolve type parameter in setmetatable using nested records (#772).
  • Ignore non-literal booleans in table key declarations (#816).
  • Type variables from function results also resolve arguments (#838).
  • Do not mistake missing optional argument for a vararg.
• Improved code generation
  • Generate __is-aware code for is on unions (#742).
  • Handles metamethod for __eq (#814).
• Fixes for self type
  • Fixed a nil reference exception (#824).
  • Corrected resolution of self in methods (#812).

0.24.0 - Teal Spring '24

2024-10-07

This a big release! Teal 0.24.0, codenamed "Teal Spring '24" as a nod to the coolest language release name ever ("Clipper Summer '87"), is a culmination of work that has spanned multiple years, and it would not be possible without the amazing feedback given by the community on the next branch, where this was developed. This release does include that "lot of new code" that I wanted to merge in the "near future", which I referred to in the changelog entry for the previous release. It is nice to see it all coming together!

The main feature is the addition of interfaces, which introduces a model for subtyping table types in the language. That should allow for representing the various kinds of object models that are used across the Lua ecosystem, without promoting any particular class/object system over the others. Most of the other changes, such as macro expressions, came along as related features built to support this. The support for optional argument markers is a stop towards stricter type safety, and the addition of pragma markers to control this feature is a statement of intent for allowing gradual transitions as the language evolves. All in all, the goal is to make the 2024 edition of Teal a safer and more pleasant language to use.

And yes, an October release is called Spring because it is now spring in the southern hemisphere. :)

This release features commits by François Perrad, Victor Ilchev and Hisham Muhammad.

What's New

Language

• Interfaces: you can now declare abstract interfaces, and record types can implement them. This allows you to declare subtyping relations, and better support inheritance models (e.g. local record Circle is Shape).
  • Records and interfaces may declare a where clause with an expression over self, which allows the is operator to discriminate the type.
  • With discriminated record types, it is now possible to declare unions over multiple record types.
  • "Arrayrecords" are no longer a distinct type: they are just records that implement an array interface (e.g. local record R is {T})
  • Type variables in functions can now have constraints on interfaces (e.g. function my_func<F is MyInterface>(...))
  • self is now a valid type that can be used when declaring arguments in functions declared in interfaces and records
    • When a record is declared to be a subtype of an interface using is, any function arguments using self in the parent interface type will then resolve to the child record's type.
• Optional/required arguments in function calls - functions may declare arguments as optional, affecting the required arity of function calls. The rightmost arguments of a function can have their variable names annotated with a ? sign, indicating that the argument does not need to be passed in a function call. This refers only to the presence of the argument in a call, and not to its type or nullability: a required argument may still be called with an explicit null, but an optional argument may be elided.
  • In previous versions of Teal, all function arguments were effectively optional. This means that Teal is now stricter which checking for function calls. You can use --feat-arity=off in the command line or feat_arity = "off" in tlconfig.lua to obtain the previous behavior.
  • To convert code that uses the old arity checking rules to the new behavior, you can also use compiler pragmas in the code, --#pragma arity off and --#pragma arity off to disable or enable stricter arity checks.
• Macro expressions: you can declare a restricted form of function called a macroexp, which is always expanded inline. These can also be used to declare compile-time metamethods, which expand without requiring a metatable at runtime. The where clauses used in interfaces and records are syntax sugar for macro expressions that implement a pseudo-metamethod __is.
• Dynamic require calls that do not take a module name as a literal string are now allowed, and return any; you can load a static type definition using local type MyType = require("...") and then cast your dynamic require like so: local my_mod = require(var) as MyType
• The type system is more nominal: all named types are now treated nominally, except for unions, which are always type aliases. Previously record types were nominal, but a named typed that resolved to a primitive such as integer was structural. There are still subleties on the rules for when a local type produces a new distinct type or an alias; they are explained in the docs.
• The <total> attribute for variables can now only be applied when initializing variables with literal tables. This is a minor breaking change, but the usefulness of this attribute in other cases was very limited, and it also produced misleading results.
• Improved type signatures in the standard library
  • select produces variadic returns

API

• Simplified API in the tl module.
  • The 0.15 API is still supported for backwards compatibility.

Tooling

• tl build was removed. Cyan should be used instead as the build tool for Teal projects.

Fixes

• Fix commits included in this release refer both to bugs present in the master branch as well as fixes specific to the 0.24 series, reported by the community during the beta testing of this release. The Git history and the GitHub issues list contain a more detailed accounting of the bugfixes that went into this release. Some of the fixes include:
  • tl check now reports if the input file does not exist.
  • Reporting location of the end of an if block correctly.
  • No longer crash if a require() epression fails to resolve (#778).
  • tl types now reports the types of variables in for loops.
  • Improved error message when calling functions with insufficient arguments.
  • Disallowing using a base type as a type variable name.
  • Type arguments resolving correctly in recursive functions.
  • Type arguments resolving correctly in nested records (#754).
  • or type inference between types with a subtyping relation resolves to whichever is the larger type.
  • Reporting an error if an iterator used in a generic for does not declare a return value type (#736).
  • When checking <total> values, no longer reporting record function and metamethods as missing fields (#749).
  • Localizing a record no longer makes the local a type (#759).
  • Bad assignments of record tables are reported (#752).
  • Nominal type alias declarations work as expected (#238).
  • Nominals with generics can be resolved correcty (#777).
  • Nested types are not closed too early (#775).
  • Not failing when resolving nested empty tables.
  • Exporting generics and type aliases from modules correctly using return at the toplevel (#804).

0.15.3

2023-11-05

It's been a long time since the last release! Lots of fixes got merged in, and there's a lot of new code that I want to merge in the near future. So, let's get a more fix-oriented release out before more significant changes.

This release features commits by @JLPLabs, François Perrad, JR Mitchell and Hisham Muhammad.

What's New

Language

• Accept return-like syntax for vararg inputs in function type signatures (e.g. function(string...): string...)
• Parser no longer accepts annotations (e.g. <const>) in for-in variables. It used to accept but ignore them before.
• New warning for or between incompatible types in a context where no union is expected.
• Record functions now implicitly inherit type variables from its parent record's definition. (#669)
• Standard library improvements:
  • improved return values for debug.getlocal
  • improvements to utf8.codes signature
  • io.write and file:write signatures also accept numbers
  • file:close signature now produces Lua 5.2+ returns (and matches Lua 5.2+ behavior thanks to update in Compat-5.3 library)
  • file reader functions (io.read, io.lines, FILE:read, FILE:lines) now support the "n"/"*n" pattern

Fixes

• No longer produces spurious warnings when using methods with pcall. (#668)
• Better acceptance of record and enum as soft keywords.
• is inference now takes into account that unions also imply nil, therefore accepting an else case even if all cases of an union are tested in if/else if branches. (#699)
• :-style function calls also check for the __index metamethod. Also avoids mistaking __index for an incorrect method use.
• Resolves type arguments when both types in an or expression match the expected type. (#709)
• Checks records nominally when resolving metamethods for operators. (#710)
• Avoids confusing a localized global for an automatic type narrowing when reporting unused variables.
• When generating compatibility bit32 code, always do it, even for invalid variables, instead of emitting incompatible operators.
• Compiler no longer crashes if type variable resolution fails when setting an inference location.
• Compiler no longer crashes when checking for a reassigned const global.

Code generation

• Unused local types no longer emit dummy variables.

Tooling

• tl for many files is much faster as it avoids running the GC on every file.
• Package loader now populates the ... tuple

0.15.2

2023-04-27

This is primarily a bugfix release, but it does include some significant quality-of-life improvements when using record methods.

This release features commits by JR Mitchell, @IcyLava and Hisham Muhammad.

What's New

Language

• Improved checks over uses of self in forward-declared methods:
  • In a record declaration, when fields of type function are declared within a and they have a matching self first argument, those are now treated as methods (similar to explicit function R:method declarations using colon-notation), so misuses of : versus . can be detected in those as well.
• Warn when invoking a method as a function, even if the type of the first non-self argument matches.
• Standard library improvements:
  • Add optional third argument for string.rep

API

• Public signature of tl.gen features second return value of type Result

Fixes

• Acept record method declaration for nested records. (#648)
• Do not consider an inner type to be a missing key when declaring a total table. (#647)
• Change inference order in function calls to better match programmer intent: infer self (which is usually explicitly given) before return values (which are implied by context).
• Preserve narrowed union in a loop if the variable is not assigned. (#617)
• Don't miss a "unused variable" warning when it is a narrowed union.
• Fixes the detection of record method redeclaration. (#620)
• Fixes the error message when number of return arguments is mismatched. (#618)

0.15.1

2023-01-23

A minor bugfix release, thanks to feedback received upon the release of 0.15.03

This release features commits by Hisham Muhammad.

What's New

Fixes

• Fixes resolution of nominals across scope levels.
• Fixes a crash when resolving nested records in a record function. (#615)
• Avoid spurious inference warnings in local declarations.

0.15.0

2023-01-20

Two new language features, a bunch of inference improvements, some more stricter checks for correctness, and a bunch of fixes! There's a lot to unpack in this release, but all changes should be backwards-compatible for correct code, so migration should be smooth for end-users of the compiler.

However, if you're using tl module API directly, please note that there are some API changes, listed below.

This release features commits by Li Jin, Carl Lei, Yang Li, Pierre Chapuis, @lenscas, Stéphane Veyret, and Hisham Muhammad.

What's New

Language

• Type-only require:
  • Adds new syntax for requiring a module's exported type without generating a require() call in the output Lua: local type MyType = require("mytype") -- circular definitions of local type-required types are allowed, as long as the type is only referenced but its contents are not dereferenced.
• New variable attribute <total>:
  • It declares a const variable with a table where the domain of its keys are totally declared.
  • This check can only be applied when a literal table is given at the time of variable initialization, and only for table types with well-known finite domains: maps with enum keys, maps with boolean keys, records.
  • Note that the requirement is that keys are declared: they may still be explicitly declared to be nil.
• Type inference improvements:
  • Improved flow-typing in if blocks - if a block ends with return, then the remainder of the function can infer the negation of its condition.
  • In contexts where the expected type of an expression is known (e.g. assignments, declarations with explicit type signatures), the return type a function call can now determine the type argument of a function.
    • In particular, local x: T = setmetatable({}, mt) can now infer that {} is T without a cast.
  • When initializing a union with a value, that value is now used by the flow-typing engine to narrow the variable's concrete known type.
• Local functions can be forward-declared with a local variable declaration and then implemented with bare function notation, more similarly to how record functions (and Lua functions) work.
• Handling of . and index notations is now more consistent for both maps and records:
  • Map keys can now use .-notation like records, and get the same checks (e.g. if a key type is a valid enum)
  • __index metamethod works for .-notation as well.
• Some stricter checks:
  • Unused type arguments in function signatures are now flagged as an error.
  • Using the # operator on a numeric-keyed map now produces a warning, and on a non-numeric-keyed map it produces an error.
  • Redeclaration of boolean keys in a map literal are now an error.
  • Cannot declare a union between multiple tuple types as these can't be discriminated.
  • Cannot redeclare a record method with different type signatures; produces a warning when redeclaring with the same type signature.
• Standard library improvements:
  • pcall and xpcall have vararg return types

Fixes

• Fixed check between or expression and nominal unions.
• Fixed function call return values when returning unions with type arguments. (#604)
• Fixed an error when exporting type aliases. (#586)
• __call metamethods that are declared using a type alias now resolve correctly. (#605)
• Generic return types are more consistenly checked, potentially reporting errors that went undetected before.
• Fixed type variable name conflicts in record functions, ensuring nested uses of generic record functions using type variables don't cause conflicts. (#560)
• Fixed the inference of type arguments in return values. (#512)
• Fixed the error message for redefined functions. (#566)
• Fixed a case where a userdata record type is not resolved properly. (#585)
• Fixed some issues with the <close> attribute.
• tl warnings no longer misses some warning types.

Code generation

• Report error on unterminated long comments instead of generating invalid code.
• Cleaner code is produced for is nil checks.

API

API changes for more consistent processing of syntax errors:

• tl.lex changed: it now returns an {Error} array instead of a list of error Tokens.
  • from function tl.lex(input: string): {Token}, {Token}
  • to function tl.lex(input: string, filename: string): {Token}, {Error}
• tl.parse_program changed: it no longer returns the first integer argument, which as always ignored by every caller.
  • from function tl.parse_program(tokens: {Token}, errs: {Error}, filename: string): integer, Node, {string}
  • to function tl.parse_program(tokens: {Token}, errs: {Error}, filename: string): Node, {string}
• tl.parse is a new function that combines tl.lex and tl.parse_program the right way, avoiding previous mistakes; this is the preferred function to use moving forward.
  • signature: function tl.parse(input: string, filename: string): Node, {Error}, {string}

Tooling

• Better handling of newlines on Windows.
• tl types: in function calls of polymorphic functions, now the return type of the resolved function is reported.
• More informative pretty-print of polymorphic function signatures in error messages.
• More informative error message for field assignment failures.
• Improved error message for inconsistent fields (#576)
• The parser now does some lookahead heuristics to provide nicer error messages.
• The compiler now detects mis-aligned end keywords when reporting about unmatched blocks, which helps pointing to the place where a mistake actually occurred, instead of the end of the file.
• For debugging the compiler itself:
  • new environment variable mode TL_DEBUG=1 inspects AST nodes and types as program is compiled.
  • TL_DEBUG with a negative value -x will run like TL_DEBUG=1 but halt the compiler after processing input line x.

0.14.1

2022-08-23

And a week after 0.14.0, here's 0.14.1, with bugfixes to a few regressions identified by users. This is essentially a bugfix release, with a few improvements triggered via regressions or confusing error messages.

This release features commits by Hisham Muhammad.

What's New

Fixes

• Improved error reporting on declarations with missing local/global
• Ensured exp or {} with empty tables continues to work as it used to in 0.13.x, skipped more advanced flow-typing as simply returning the type of the left-hand side exp.
• Improved propagation of invalid types in unions
  • Avoids weird messages such as got X | Y, expected X | Y when "Y" is invalid in the scope, but was valid on declaration of a function argument, for example.
• Fix missing bidirectional flow of expected types in return expressions and expand it on string constants. (#553)
  • This is almost a feature as flow-checking was made smarter for string constants, but it takes the shape of a regression test because return expression checks were incomplete and caused some correct code to pass type checking before which stopped passing on 0.14.0 when some checks were extended. We further extend them here to make more valid code pass.
• Fixes a crash when resolving a "flattened" union. (#551)

0.14.0

2022-08-16

It's been a year! It was good to let the language sit for a while and see what kind of feedback we get from real world usage. This has also been an opportunity to get bug reports and fixes in, to help further stabilize the compiler.

This release features commits by Li Jin, Enrique García Cota, Patrick Desaulniers, Mark Tulley, Corey Williamson, @Koeng101 and Hisham Muhammad.

What's New

Language

• Global functions now require global function, you can no longer declare them with a bare function; this makes it more consistent with other global variables. (#500)
• Forward references for global types:
  • global type Name can be used to forward-declare a type and use it, for example, in record fields, even if it is declared in another file. (#534)
• Polymorphic functions (as declared in record methods) can be used as iterators for a generic for. (#525)
• You can no longer define a global with the same name as a local which is already in scope. (#545)
• Initial support for the __index metamethod: you can declare it as a function. (#541)
• Dropped support for the old backtick syntax for type variables.
• Type checker checks validity of Lua 5.4 <close> annotations:
  • the output target must be set to "5.4"
  • there can be only one <close> variable per declaration (to ensure correct order of __close metamethods being called)
  • the type of the variable is closable
  • globals can't be <close>
  • <close> variables can't be assigned to
• Nested type arguments are now valid syntax without requiring a disambiguating space. The parser used to reject constructs of the type X<Y<T>> due to ambiguity with >>; it is now accepted (old time C++ coders will recall this same issue with C++98!)
• Standard library improvements:
  • math.maxinteger and max.mininteger are always available (in any Lua version, with or without lua-compat-5.3 installed)

Code generation

• Local types are now elided from generated code if they are never used in a concrete value context: if you declare a local type T such as a function alias, it no longer produces a local T = {} in the Lua output.

API

• tl.pretty_print_ast now takes a TargetMode argument to specify flavor of Lua to produce in output:
  • new TargetMode for outputting Lua 5.4-specific code including <const> and <close> annotations.
• tl.load now always runs the type checker, which is needed to produce type information required to output correct code in some cases. The default behavior, however, remains backwards compatible and allows code to run in the presence of type checking errors. You can override this behavior and make tl.load return nil, err in case of type checking errors by using a "c" prefix in the mode flag (e.g. "ct", "cb", "cbt").
• tl.type_check returns two values.

Tooling

• Project CI now runs on GitHub Actions
• Windows portability improvements
  • Windows and Mac now get tested regularly in the GitHub Actions CI!
• New hint warning when the value of a function with multiple return values is being returned as part of an expression, causing the additional returns to be lost.
• Improved error messages for map errors.
• tl check avoids re-checking files already loaded in the environment: this allows you to check your global_env_def module without getting redeclaration errors.
• Build script for stand-alone binary is now included in the repository.

Fixes

• Fixed resolution of type variables to avoid clashes when nested uses of generic functions used the same type variable name. (#442)
• Map index keys are checked nominally, not structurally. (#533)
• Fixed flow checking of enums in or. (#487)
• Properly return type errors for fields when comparing records. (#456)
• Fixed a stack overflow when comparing unions with type variables. (#507)
• Fixed a stack overflow in record comparisons. (#501)
• It now reports the location of a redeclared record correctly. (#542)
• Fixed resolution of nested type aliases (#527) and nested nominals (#499).
• Fixed check of inconsistent record function declarations. (#517)
• tl.loader reports correct filename in debug information. (#508)
• Fixed error message when tlconfig.lua contains errors.
• Tables can't be assigned to record types declared to be userdata. (#460)
• Fix check of arrays of enums in overloaded record functions.
• Fixed crash when attempting to declare a record method on an unknown variable. (#470)

0.13.2

2021-07-30

A long while since the last release! This one contains a bunch of fixes, but no significant language changes. Trying to keep the language stable for a while so that we better understand what's needed and what the priorities should be, as more people use it.

This release features commits by Corey Williamson, Patrick Desaulniers, Enrique García Cota, Francisco Castro, Jason Dogariu, @factubsio @JLPLabs, @sovietKitsune, @DragonDePlatino and Hisham Muhammad.

What's New

Language

• Generic for now accepts records that implement a __call metamethod
• Allows # to be used on tuple tables
• Metamethods for __tostring, __pairs, __gc can be declared
• Standard library definition improvements:
  • collectgarbage has smarter arguments
  • error: first argument can be anything
  • os.time: accepts a table as input
  • table.concat accepts numbers in the array argument

API

• tl.load now behaves more like Lua's load, using the default environment if the fourth argument is not given.

Tooling

• Report warning for excess lvalues correctly
• tl finds ?/init.lua in its include_dir entries as well
• Updates to make test suite run on Windows
• tl --quiet silences configuration warnings
• Documentation: various fixes and improvements
  • New guide on .d.tl declaration files

Fixes

• Fixes for compat code when using --gen-target=5.1
• Various crash fixes for record method declarations:
  • Fixed crash when inferring type for self
  • Fixed crash when declaring methods on an untyped self
  • Fixed crash when redeclaring a method already declared in the record definition
• Fixed a crash when traversing a . on something that's not a record
• Error messages now report ... in variadic function types

0.13.1

2021-03-19

A quick bugfix release, to correct the behavior of global_env_def, which wasn't being properly loaded from tlconfig.lua. Getting a quick release out of the door so that people who were using preload_modules don't stay on an old version just because of that!

This release features commits by Kim Alvefur.

What's New

Tooling

• Fixed loading global_env_def from tlconfig.lua.

0.13.0

2021-03-18

A long awaited feature arrives: integers!

Teal now has a separate type integer for integers, and number continues to be the general floating-point value.

The integer type works for any Lua version, but from Teal's point of view it has unknown precision. The actual precision depends on your Lua VM: if you're running on Lua 5.3 or above, you get 64-bit integers; if you're running Lua 5.2 or below or LuaJIT, the implementation still generates regular numbers, but it checks that operations declared to work on integers will only use values declared as integers, which is useful even if the VM does not have a native integer value type.

See more details about the behavior below, as well as a quick guide to help you in the conversion process!

Apart from integers, this release features your usual assortment of tooling tweaks and bugfixes!

This release features commits by Kim Alvefur and Hisham Muhammad.

What's New

Language

• Integer type!
  • integer is a new type of undefined precision, deferring to the Lua VM
    • integer constants without a dot (e.g. 123) are of type integer
    • operations preserve the integer type according to Lua 5.4 semantics (e.g. integer + integer = integer, integer + number = number, etc.)
    • integer is a subtype of number
      • this generally means that an integer is accepted everywhere a number is expected
      • note that this does not extend to type variables in generics, which are invariant: Foo<integer> is not the same as Foo<number>
      • if a variable is of type integer, then an arbitrary number is not accepted
        • local x: integer = 1.0 doesn't work, even though the floating-point number has a valid integer representation
    • variables (and type variables) are inferred as integer when initialized with integers
      • this can happen directly (local x = 1) or indirectly (local x = math.min(i, j))
      • to infer an integral value as a number, use .0: local x = 1.0 infers a number
  • the standard library was annotated for integers
    • it only returns integers, but it always accepts floats in arguments that must be integral — this matches the behavior of the Lua standard library implementation: wherever you need to pass an integral value, you can pass an equivalent float with an integer representation, e.g. table.insert(t, 1.0, "hello") — therefore, this is also valid in Teal, but note that the validity of the float is not checked at compile time, this is a Lua standard library API check.
• Redeclared keys in table literals are now an error.
• More improvements thanks to bidirectional inference:
  • You can now make an or between values of two different types if the context expects a union.

Quick guide for existing converting code to use integers - I tried to be as careful as possible in making the transition easier, but this will undoubtedly break some of your code — don't worry, fixing it is easy. Any new error may fall into one of two categories:

1. Your value is meant to be an integer, but it is being detected as a number

• if your variables are meant to be integers (indices in an array, counters, line-column coordinates, etc.), most likely your code will already be using them as integer because local x = 0 now infers to integer.
• If you explictly declared it as local x: number, just change it to local x: integer.
• Your functions will often feature arguments and return types declared as number where they should now be integer, if they take or produce integer values.
  • This will cause, especially for return types, a line like my_integer = func() to produce an error got number, expected integer; func needs to be changed from function func(): number to function func(): integer.
• To convert floating-point numbers to integers you can use math library functions such as math.floor().

2. Your value is meant to be a floating-point number, but it is being detected as an integer

• if your variables are meant to be floating-point and Teal is inferring them as integer because of their initialization value, the easiest thing is to change them to floating-point constants, changing from local dx = 0 to local dx = 0.0
• Due to subtyping, integers generally work wherever numbers are required, but if you need to convert an integer to a number in an invariant context such as a type variable in a generic, you can force it with a cast (i as number).

API

• new API function tl.version(), which returns the version of the compiler.
• make unknowns a kind of warning, not a separate array
• only ever return Result values, do not take them as inputs
• each Result only contains errors for the given file
  • use env.loaded (and env.loaded_order) to traverse all results and get all errors

Tooling

• renamed preload_modules (an array) to global_env_def (a single entry). This option caused some confusion before, so we reworked the documentation to better explain its intent.
  • For example, to load global definitions for Love2D from a file love.d.tl, use global_env_def = "love" in your tlconfig.lua file.
• tl run -l <module> <script> (long form --require <module>)
  • works like lua -l; type checks the module and requires it prior to running the script.
• tl gen --check now reports warnings
• When processing .lua files, unknown variables are now a type of warning, so you can enable and disable them using the usual warning features from the CLI and tlconfig.lua
• Some performance improvements in the compiler itself, thanks to some profile-directed optimization (in other words, putting the most-used branches first in long if/elseif chains).
• tl types now produces its JSON output in a stable order
• tl types now returns more information
  • types in function names, for variables

Fixes

• Nested type alias now work as expected
• Fix a crash when doing flow inference on inexistant variables (#409)
• Fix partial resolution of type arguments
• Some fixes related to arrayrecords
  • Nested types now work correctly with arrayrecords
  • Fixed use of self in functions declared in arrayrecords

0.12.0

2021-02-27

Time for a new release, with some significant updates to make the behavior of the language more smooth.

Language-wise, the big change is bidirectional inference for table literals, meaning that the types of literal tables (that is, the ones you write with { ... } in your code) now get more precise types when they are defined in contexts that have type declarations, such as variables with explicit types, or function arguments where the types are known.

There have been also various improvements in the API and tooling departments, all aiming to produce better development experience -- do keep an eye for exciting things thet are in the works in this area!

This release features commits by Patrick Desaulniers, Corey Williamson, and Hisham Muhammad.

What's New

Language

• Bidirectional inference for table literals
  • Type information propagates outside-in when a table literal is declared as the rhs value of a variable declaration, assignment or as a function argument.
  • This fixed various outstanding bugs where unintuitive behavior was observed.
• local type T1 = T2 now makes nominal T1 an alias for nominal type T2, and not a separate type (same applies to global type).

API

• preload_modules functionality was moved from tl.process into tl.init_env, so that API clients that use the lower-level operations can preload modules.
• tl.get_token_at can return the token given a token list and a position.

Tooling

• tl gen now has a --check flag, which makes it reject code that does not typecheck and not generate the output.
• Warnings output is now presented in a stable order.
• tl types has had various improvements generating better data for editor integration:
  • The symbols list is much shorter as empty or redundant scopes are eliminated.
  • Incomplete expressions now output type information for the fragment that could be parsed.
  • Function types look nicer in error messages and tooling.

Fixes

• Unions of nominal types now reduce considering aliasing.
• Various fixes for the behavior of tl types.
  • The top level scope is now correctly closed at the end of file.
  • Symbols list is now properly sorted.
  • Function types point to the correct filenames.

0.11.2

2021-02-14

More bugfixes! This includes some behavior fixes in the flow inference, so some code that wasn't accepted before may be accepted now and vice-versa, but the overall behavior is more correct now. Apart from this, no language changes other than fixes.

This release features commits by Corey Williamson, @JLPLabs and Hisham Muhammad.

What's New

Language

• Some more propagation of "truthiness" when flow-typing expressions:
  • assert is now known by the compiler to be truthy when performing flow propagation of type information. This means that, for example, given x of type A | B, in an expression of the form x is A and assert(exp1(x)) or exp2(x), x will be known to be of type B in exp2(x).
• t or {} is now only valid for table types
• Standard library improvements
  • math.randomseed accepts Lua 5.4 second argument

API

• get_types now returns numeric type codes, and more complete type data for IDE integration consumption
• The parser collects the list of required modules, for use by later use by build tooling
• The type checker now collects the list of filenames resolved by require, for use by build tooling

Tooling

• Performance improvements for the lexer
• Performance improvements for the JSON encoder used by tl types

Fixes

• tl types: proper escaping of JSON strings
• some parser fixes to avoid crashes on incorrect input

0.11.1

2021-02-07

Having great users means having great feedback! Here's a quick bugfix release addressing a few issues that were reported by the community right after the release of Teal 0.11.0.

This release features commits by Hisham Muhammad.

What's New

Fixes

• Fixed inference in cases that combine is and == (#382)
• Fixed tuple resolution in literal tables
• Fixed incorrect <const> in table inference (#383)

0.11.0

2021-02-07

The FOSDEM 2021 edition!

This new release does not include big language changes, but includes a lot of new stuff! The new tl types infrastructure for IDE tooling, build.tl support in tl build, code generation options, and tons of bugfixes.

This release features commits by Corey Williamson, @lenscas, Patrick Desaulniers and Hisham Muhammad.

What's New

Language

• The module return type can be inferred anywhere at the top-level, not only at the outermost scope (#334)
• Records are compared nominally and all other types are compared structurally
• Flow inference added to the == operator
  • Testing for a value in an if test propagates it into the block, which is especially useful for constraining a string into an enum, for example
• Standard library improvements
  • debug library

Tooling

• New experimental command: tl types,
  • It produces a JSON report designed to be consumed by IDE tooling: for each input file, it lists all types used in the source code by line and column location, all symbols declared by scope, all types and globals
  • Also includes experimental a Teal API, which is used to implement tl types:
    • tl.get_types, which produces the above report as a record
    • tl.symbols_in_scope, which given a report, a line and column, reports all symbols visible at that location.
  • This feature is still experimental because the compiler was extended to perform type checking on syntactically-incorrect inputs (because IDEs want to perform analysis on unfinished programs). Some incorrect inputs may cause the type checker it to stumble!
• Support for build.tl file in tl build, which allows you to run a build script written in Teal before your files are compiled (for example, to produce generated code)
• tl build now looks for tlconfig.lua in parent directories, so you can call it from anywhere in your project tree
• Improved error messages and reduced the number of cascading syntax errors
• The compat53 dependency is now optional (pcall-loaded) in generated Lua code. You can make it required or disable it completely using gen_compat in tlconfig.lua and --gen-compat={required|optional|off}
• You can now target the Lua version of the generated code with gen_target and --gen-target. Supported modes are 5.1 (for LuaJIT, Lua 5.1 and 5.2) and 5.3 for (Lua 5.3 and Lua 5.4).
• Friendly warnings on misuse of pairs/ipairs
• Type checker now runs in the package loader

Fixes

• Preserves explicit semicolons in the input, to deal correctly with Lua grammar ambiguity
• New inference engine for is operator
  • Does negation correctly implementing DeMorgan's laws
• Fixed is for type arguments
• Fixed resolution of metamethod fields in nested types (#326)
• Fixed type comparison for tuple elements
• Fixed invariant comparison between empty tables and nominals (#332)
• Fixed precedence of + relative to ..
• A large number of parser fixes on bad input corner cases, thanks to fuzz testing and user feedback, prompted by the tl types work!

0.10.1

2021-01-07

Fixes, lots of fixes! We shipped a bunch of stuff in 0.10, so it's time to clean some rough edges, thanks to the great feedback we've received in that release. No big changes in the language this time (other than some things that should have worked but didn't now do!). In the tooling department, we now have configurable warnings, so you can enable or disable them by category. Also, stay tuned for the next Teal meetup later this month!

This release features commits by Darren Jennings, Corey Williamson and Hisham Muhammad.

What's New

Language

• Allow using metamethods such as __call and operators on the record prototype itself (#313)
• Maps are now invariant on key and value types (#318)
• It is now an error to declare too many iteration variables in a for-in construct
• Some standard library definitions were changed from using polymorphic function to using union types (#317)

Tooling

• Warning categories
  • You can disable specific warning categories such as redeclared variables with the --wdisable flag or with the disable_warnings entry in tlconfig.lua
  • You can list existing warning categories with tl warnings
• You can turn warnings into errors with --werror
• Nicer error message when type is declared without a local or global qualifier

Fixes

• Fixed a parser crash on incomplete expressions
• Nested record prototypes can be used everywhere record prototypes can
• Fixed a leak of type variables when defining generic functions (#322)
• Fixed resolution of type arguments in recursive type definitions to avoid crashing the compiler
• Ensured that n-ary function returns don't leak into variable declaration types (#309)
• Fix is code generation for userdata

0.10.0

2020-12-31

We've had a lot of activity in Teal this month, so let's wrap it with a new release! We had our very first Teal meetup (recording), a Twitch stream session, lots of activity in our Gitter chat with folks from the community building various projects, and providing great feedback which helped us prioritize and shape the evolution of the language. So let's celebrate with Teal 0.10.0, which packs a lot of new stuff! Happy New Year! 🎉

This release features commits by Enrique García Cota, Darren Jennings, Corey Williamson and Hisham Muhammad.

What's New

Language

• Metamethods!
  • Records can now declare metamethods as part of their definitions, which informs the Teal type checker about supported operations for that record type. (#299)
  • Metatables are not automatically attached, you still need to use setmetatable: check the documentation for an example on using records with metamethods and metatables.
  • Operator metamethods for // and bitwise ops are supported even when running Teal on top of Lua 5.1.
• Userdata records
  • The practical difference, as far as type checking goes, is that they no longer count as a "table" type in unions.
• or expressions now accept subtypes: for example, an or between a union and one of its elements is now accepted.
• Some breaking changes for cleaning things up:
  • The language now rejects unknown variable annotations. That includes <close>, which is not currently supported. Note that Teal does support the <const> annotation (for all Lua versions) and performs the check at compile time.
  • Dropped. support for record and enum definitions inside table literals. This was a remnant from when variable and type definitions were mixed. Now all record and enum definitions need to happen inside a local type or global type definition (and may be nested).
• Standard library definition improvements:
  • math.log accepts a second argument

Tooling

• Compiler warnings!
  • The Teal compiler now features a warning system, and reports on unused variables.
• Teal Playground integration in the Teal repository
  • Now, every PR triggers a Github Action that produces a link to a Teal Playground which allows you to test the compiler changes introduced by the PR right from your browser!
• tl build now returns a non-zero error code on type errors

Fixes

• Detects a bad use of : without a proper () call (#282)
• Fixed type inference for variadic return in for loops (#293)
• Always check for union validity after type arguments are resolved when declaring a record (#290)
• No longer suggest "consider using an enum" when indexing non-records
• Fixes for control-flow based inference
  • Fix expression inference in elseif
  • Propagate facts across parentheses
• Standard library definition fixes:
  • os.date second argument was fixed

0.9.0

2020-12-16

Three months after 0.8, it's time to release Teal 0.9! It features language improvements, bugfixes, new contributors.

This release features commits by Domingo Alvarez Duarte, Corey Williamson, Pierre Chapuis and Hisham Muhammad.

What's New

Language

• New tuple type!
  • You can declare a type such as local t: {string, number} = {"hi", 1} and then t[1] gets correctly resolved as string and t[2] as number. t[x] with an unknown x gets resolved as string | number.
  • Inference between arrays and tuples allows for some automatic conversions.
• record declarations now accept arbitrary strings as field names, using square brackets and string notations, similar to Lua tables: [ "end" ] : string
• Support for the // integer division operator
  • This is also supported for target VMs that do not support it natively! For those environments, it outputs math.floor(x / y) in the Lua code.
• Additions and tweaks to the standard library definitions:
  • string.gsub function argument return values

Tooling

• Error messages of the type X is not a X (when two different nominal types happen to have the same name) are now disambiguated by presenting the filenames and locations of the two different declarations, as in X (declared in foo.tl:9:2) is not a X (declared in bar.tl:8:2)
• The tl compiler module now exposes some of its external types for use by tooling (such as the tl CLI script)
• Compiler now generates compatibility code using bit32 library (part of compat53) for target VMs that do not support bitwise operators natively.
• Performance improvements in the compiler!
  • ./tl check tl.tl went from avg 612ms in 0.8.2 to 315ms
• CI now tests Teal with Lua 5.4 as well.

Fixes

• Fixed the support for bitwise xor operator ~
• Fixed the support for escapes in string literals, including Unicode escapes.
• Various fixes to the inference of unions.
  • Fixed invariant type comparisons for union types.
  • It now skips nil correctly when expanding union types: For example, { 5, nil } is now correctly inferred as { number } instead of { number | nil }, because nil is valid for all types.
• Cleaned up shadowed variable declarations in the compiler.
• Cleaned up and added more extensive test cases for subtyping rules for nil, any, union and intersection types, and caught some edge cases in the process.

0.8.2

2020-11-06

This is another bugfix release.

This release features commits by Hisham Muhammad, Corey Williamson and fang.

What's New

Fixes

• tl now caches required modules to not load code more than once (#245)
• fixed a compiler crash using math.atan
• tl now uses loadstring instead of require to load config, to avoid issues with LUA_PATH
• do not shadow argument types with function arguments
• expand tuples but not nominals in return types (#249)
• fix is inference on else block when using nominal types (#250)
• for accepts a function call that returns a nominal which resolves to an iterator. (#183)
• fix invariant type checking of records
• various fixes for the lexer pretty-printer

0.8.1

2020-10-24

This is a small bugfix release, to get some of the recent fixes out in the default package.

This release features commits by Hisham Muhammad, Corey Williamson and Casper.

What's New

Language

• Standard library definition improvements: debug.traceback 3-argument form and __name metatable field

Tooling

• Added a simple type checking for config entries in tlconfig.lua

Fixes

• Fixed a crash when detecting wrong use of self on a method with no arguments. (#228)
• Fixed the declaration of type aliases for nominals, which was causing a stack overflow. (#238)
• Only infer an array if we can infer its elements: When resolving the type of a table literal, a function with no returns produces an empty tuple, and that does not give us enough data to resolve a type. (#234)
• Improved cleanup for the test suite.

0.8.0

2020-09-18

Some big language changes in this release! Type declarations were made more consistent, with the introduction of local type T = D for declaring a type T given a definition D (likewise for global type), instead of pretending that type declarations were assignments. This allowed us to remove the kludgy functiontype word (the definition for function types is the same as used for function arguments: local type F = function()···

This release also includes major tooling improvements! The tl CLI received major attention, with a new command tl build and many new options in tlconfig.lua, making tl more comfortable to use for building projects. The tl module also received some API improvements for programmatic use of the compiler.

This release features commits by Darren Jennings, Patrick Desaulniers, Corey Williamson, Chris West and Hisham Muhammad.

What's New

Language changes

• local type and global type syntax for type declarations
• Dropped support for functiontype: use function instead
• Shorthand syntax forms for declarations, similar to local function in Lua:
  • local record R as a synonym for local type R = record (same for global)
  • local enum E as a synonym for local type E = enum (same for global)
  • Shorthand forms are also accepted nested inside records
• Extended flow-based inference for empty tables: now when declaring a variable with an empty table (local V = {}), if its first use (lexically) is as an argument to a function, the compiler will infer the argument type to the variable
• Enums can be indexed with string methods
• Lots of additions and tweaks to the standard library definitions:
  • collectgarbage
  • coroutine.close
  • math.atan overload
  • the many metamethods in metatable definitions
  • Fixed declaration of select()

Tooling

• New command tl build, which is able to compile multiple files at once, following configuration in tlconfig.lua
• tl run passes arguments to script, populating ...
• tl gen: new flag -o, --output
• Many newly supported options in tlconfig.lua:
  • build_dir
  • source_dir
  • files
  • include
  • exclude
  • include_dir (new name of the previous include)
  • skip_compat53
• New functions in the tl module API:
  • tl.gen, a high-level function for generating Lua code from Teal code, akin to tl gen on the CLI
  • tl.process_string, a lower-level driver function which produces the result data structure including the AST for later processing

Fixes

• Fixed a file handle leak in tl.process
• Initial newlines from input file are preserved in the generated output file, so that line numbers match in stack traces produced at runtime
• It now reports error when ... is used in non-vararg functions
• Stricter type checks:
  • no longer accepts indexing a record with an arbitrary string
  • no longer accepts matching a map as a record
• Fixed resolution of multiple labels
• Better handling of varargs for for in iterators
• Parser fixes:
  • Accept () as a return type in a function declaration
  • Require separators in key/value table constructors
  • Fix acceptance of a stray separator in table constructors (accepted) and function calls (not accepted)

0.7.1

2020-06-14

A lot of important bugfixes driven by community reports!

Starting with this release, version numbers in the 0.x series will indicate the presence of breaking changes when bumping the second number (0.x.0), and both bugfixes and compatible additions when bumping the third number (0.x.y). This should make it easier to see when a release breaks something.

This release adds new features but introduces no breaking changes, so we're calling it 0.7.1.

What's New

Language changes

• support tuples in as operator for casting vararg returns: you can now cast the return of variadic functions with a parenthesized list of types
• semantics of scope of until now matches that of Lua
• Standard library:
  • Fixed return type of load

Tooling

• tl CLI:
  • New flag --version
  • New flag -q, --quiet
• tl module:
  • New function tl.load which is like Lua's load() but enables loading Teal code

Documentation

• Various fixes in the grammar definition

Fixes

• Fixes the resolution of generic types by delaying the resolution of type arguments
• Fixes parsing of paranthesized function return with varargs
• Does not stop parsing the input toplevel when a stray end is found
• Avoids a compiler crash when type checking call returns in a return statement
• Fixes an error when parsing invalid function arguments
• Fixes a crash in flow analysis when a variable does not exist

0.7.0

2020-06-08

This release had a bunch of community contributions!

What's New

Language changes

• thread is a new primitive type for representing coroutines
• Disallow unions of multiple function types, applying a similar restriction that was already in place for table types. These can't be efficiently destructured at runtime with is.
• Lots of additions to the standard library:
  • more overloads for the load function
  • loadfile and dofile functions
  • coroutine library
  • More math functions: tointeger, type and ult
  • math variables: maxinteger and mininteger
  • improvement the type definition of pcall
  • xpcall

Tooling

• tl now reports when there is a syntax error loading tlconfig.lua

Fixes

• A functiontype declaration can now refer to itself.
• Nominals declared in nested types now resolve correctly.

0.6.0

2020-06-03

What's New

Language changes

• Completed definitions of the math table to the standard library

Fixes

• Resolve arrays of unions, and flatten unions of unions

0.5.2

2020-05-31

More bugfixes!

Fixes

• An important fix for the code generation of table literals: it was causing incorrect Lua output for arrays with expanded contents, such as {...}
• Resolution of pcall now recurses: the compiler can now handle a pcalled require correctly
• Better error messages for errors using require: do not report "module not found" when a module was found but does not report type information.

0.5.1

2020-05-29

Since I was on a roll doing bugfixes, here's a quick version bump!

Fixes

• Detect and report unresolved nested nominal types
• Fix scope restriction for record functions
• Standard library tables can now be required with require()

0.5.0

2020-05-29

This release does not include a lot of changes, but it does change the rules for exporting types across modules, so it is worth the middle-number bump.

What's new

Language changes

• Types declared as local can be exported in modules
• Types that are local to a module and which are used in function signatures (e.g. as return types) can be destructured from requiring modules. This already partially worked before, but it required the variable to be used in the original module to force a type resolution.
  • Generics still require more work, but non-generic types should be propagating as described above. Generic types export correctly if made part of the module record definition.

Fixes

• Fixed a parsing error when a colon in a variable declaration was not followed by a type list

0.4.2

2020-05-18

Another collection of bugfixes!

Fixes

• Report error when a required module is not found
• Detects unresolved nominal types
• Fixes when using record type object as a record instance itself
• Fixes in the expansion of the type of a table literal
• Fixes the indentation in generated code
• More standard library additions
• Improved/fixed error messages

0.4.1

2020-05-05

Fixes a regression in record functions.

0.4.0

2020-05-03

What's new

Language changes

• Record definitions can be nested: this should make declarations of types in modules more natural

Tooling

• Improvement in the position of error messages

0.3.0

2020-04-27

This is the first release with the simplified syntax for generics, without requiring backticks!

What's new

Besides the usual bugfixes (see the Git history for details), here are the main changes:

Language changes

• Type variables no longer need backticks: you can declare function<T, U>(x: T): U and use T and U as types inside the function
• Base type declarations can contain parentheses for clarity, e.g. {string: (string|number)}
• More standard library typing improvements

Tooling

• --include/-I flag for including directories to the module search path
• tl run now auto-invokes the Teal package loader, so .tl files running with it can require() other .tl files without needing to use tl gen to generate .lua files first.
• tl run can also pass arguments to the running program again

0.2.0

2020-04-08

This is the first release where the language is officially named Teal!

What's new

Lots of bugfixes, as well as language changes, tooling improvements and beginnings of documentation!

Language changes

• Union types, still restricted (can only union between at most one table type and a non-table type -- in other words, type resolution at runtime happens using the Lua type())
  • is operator for specializing union types with a test
• goto and labels
• Type variables need to be declared in functions with angle brackets: function<...> (this fixes scoping rules)
• global function is now valid syntax
• Accepts any element type on a table typed {any:any}.
• Booleans are stricter
• Disallow extending records with functions outside of original scope
• Standard library typing improvements

Tooling

• New command-line parser using argparse, typecheck using tl check
• -l command line option for requiring libraries
• --skip-compat53 flag
• Detects lua hashbang to enter lax mode

0.1.0

2020-02-02

First tagged release! Announced at FOSDEM 2020.

What's new

• Everything!