add c-style typedef and a built-in string alias

typedef T name; binds name to the type record of T, at the top level or
in a function (scoped to its block). string is a built-in alias for char*.
A type name straight before , or ) in a parameter list is the parameter's
name, so fn f(string) still works. The language server shows typedef T
name; on hover and highlights typedef as a keyword.

1 files changed, 3 insertions, 1 deletions

diff --git a/README.md b/README.md
index 235fedb..2e579d2 100644
--- a/README.md
+++ b/README.md
@@ -169,6 +169,8 @@ fn main() {
 
 declarations are C-style, type first: `int a = 1, b;`, `node* p = rt.new(node);`, `char[4] buf;`, `point origin;`. `let` declares without a type: it infers `char*` from a word-string literal and `bstr` from a packed byte-string literal, infers other pointers and function types from the initializer, uses a pointer alias for an in-place array or struct, and keeps numbers as plain words. `let a[10];` is an untyped array. `const k = 5;` inside a function is a local constant with no type: it takes the initializer's type, needs an initializer, and can't be assigned. statements are declarations, `if`/`else`, `while`, `do`/`while`, `for`, `switch`, `break`, `continue`, `return`, `{ }` blocks, `asm { }` and expressions. `do` body `while (` cond `);` runs the body once before the test, and `continue` jumps to the test. `enum color { RED, GREEN = 5, BLUE };` makes global constants, and `color` is a type of its own in typed code (`typecheck on;`): a member takes the enum, a plain int does not become a `color`, and a `color` still becomes an `int`. untyped code treats the members as plain ints. each member is also reached as `color.BLUE`, in an expression or a `case` label. a member can carry fields too: `enum shape { circle { int r; }, rect { int w; int h; }, dot };` makes the constructors `shape.circle(3)` and `shape.rect(4, 5)`, which return an owned `shape*`, and `shape.dot()`. the tag is the word at offset 0 of the object. a `switch` over a `shape*` matches a member with `case circle(r):`, which binds its fields in that arm only. a switch on a tagged enum that leaves out a member and has no `default` gets a warning on its line (not an error). `(T)e` is a cast with the same meaning as `e as T`: the bits stay, the type changes. it has to be a simple type the parser can see in a few tokens, `int` or `*node`, not a nested array. `include "path";` reads a file and compiles it at that point, signatures first, so a library can live in its own file. each file has its own namespace and imports; dependencies included by a file do not import into the caller. `u`, `m` and `d` are ordinary names. a tag is `.u`, `.m` or `.d`, and `u*x` with no space before the star is still a recast. `switch (e) { case 1, 2: ... default: ... }` takes constant labels, and its cases don't fall through: each ends where the next begins, and `break` leaves early. operators follow C precedence, including `c ? a : b`, plus `p.x` and `p->x` (the same thing: `.` goes through a pointer on its own), `e as T` to change a type without changing the bits, and the casts below. comparisons and `&& ||` give 0 or 1. `/`, `%` and `<<` compile to native enhancement opcodes. character literals, `0x` hex and the usual escapes are there.
 
+`typedef T name;` gives a type another name, as in c, at the top level or inside a function (where it lasts to the end of its block, like a local): `typedef node* link;`, `typedef int[4] quad;`, `typedef int(int, int) binop;`, `typedef list<int> ints;`. `type name = T;` says the same thing. a typedef is only a new spelling: `link` and `node*` are the very same type record, so they mix freely in declarations, parameters, results, casts, `sizeof`, struct fields, generic arguments and `typecheck on;` code, and they print as the target type. `T` can be any type the parser accepts, but not a tag (`.u`, `.m` and `.d` belong to a declaration). a typedef can't name a type that isn't declared yet, so a struct comes before the typedefs of its pointers; using a name that is already defined is an error, and a typedef of `void` is `void` (a variable of it is the usual error). `string` is built in as a typedef of `char*`, so `string s = "hi";` and `string f(string a)` work with no declaration; a function, variable or parameter of the same name shadows it.
+
 functions are declared like C, return type first: `int f(int x)`, `node*.u make()`, `.u grab()` (a tag on its own), `void log(char* s)`. `fn f(a, b)` starts without explicit parameter or return types; constraints from calls and returned values propagate through callers and callees until inference reaches a fixed point, including recursive calls anchored by typed callees. conflicting argument types or an unknown reassignment leave the affected type unresolved instead of choosing a type. the learning example [32](examples/learn/32-inferred-calls.zc) shows this propagation and an owned raw-list return. a generic function lists its type parameters after its name, `T first<T>(*list<T> l)`, the same place a call gives explicit ones, `first<int>(l)`. the return type can use them before they're declared: while it's read, an unknown name is taken as a type parameter, and the list after the name has to confirm it. function types are written the same way, `int(int, *char)`, and `fn(int)` for one that returns a word. the earlier `fn f(...) -> T` spelling is gone.
 
 array types put the element type first. `T[n]` has its size in the type and lives in place. `T[]` also lives in place; its length is inferred from an initializer such as `int[] a = {1, 2, 3};` and cannot grow. `T[?]` can also be initialized in a function with a list, such as `int[?] a = {1, 2};`. it is a growable array: a small handle object that owns its items, made with `rt.new(T[?])` or `rt.new(T[?], n)`, indexed with a bounds check, and changed with `push(a, x)`, `pop(a)` and `resize(a, n)`. `len(a)` works on both (for `T[n]` it's the constant) and `cap(a)` gives the room before the next grow. `fixed T[?]` is a `T[?]` that can't change size: `rt.new(fixed T[?], n)` needs the length, and `push`, `pop` and `resize` on it are compile errors. a `fixed T[?]` can't be passed where a `T[?]` is expected, the other way round is fine, and a constant index outside a `T[n]` is caught at compile time. the items belong to the array, so freeing it frees them, and objects stored into a `T*[?]` are its children like any container's.
@@ -294,7 +296,7 @@ the kinds are `word`, `int`, `char`, `bool`, `void`, pointers `T*`, arrays `T[n]
 
 ### pointer types
 
-a pointer type places its star after the type, like c: `int*`, `point*`, `vec<T>*`, `vec<point*>*`, `point**`. a tag follows the stars (`vec<T>*.u`, `int*.d x`). there is no prefix form: `*int` as a type is an error, and a star in front of an expression is only ever a dereference. a pointer to an array or to a function type is spelled with a `type` alias (`type row = int[3];` then `row*`), because `int*[3]` reads as an array of pointers. `tprint`, and so error messages and reflection, print the same form.
+a pointer type places its star after the type, like c: `int*`, `point*`, `vec<T>*`, `vec<point*>*`, `point**`. a tag follows the stars (`vec<T>*.u`, `int*.d x`). there is no prefix form: `*int` as a type is an error, and a star in front of an expression is only ever a dereference. a pointer to an array or to a function type is spelled with a `type` or `typedef` alias (`type row = int[3];` or `typedef int[3] row;`, then `row*`), because `int*[3]` reads as an array of pointers. `tprint`, and so error messages and reflection, print the same form.
 
 ### methods and closures