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package parser
import "../ast"
import "../lexer"
import "../token"
import "core:fmt"
import "core:mem"
import "core:testing"
Parser :: struct {
l: ^lexer.Lexer,
cur_token: token.Token,
peek_token: token.Token,
errors: [dynamic]string,
}
new :: proc(l: ^lexer.Lexer) -> Parser {
p := Parser{l, token.Illegal{}, token.Illegal{}, make([dynamic]string, context.temp_allocator)}
next_token(&p)
next_token(&p)
return p
}
next_token :: proc(p: ^Parser) {
p.cur_token = p.peek_token
p.peek_token = lexer.next_token(p.l)
}
cur_token_is :: proc(p: ^Parser, $T: typeid) -> bool {
_, ok := p.cur_token.(T)
return ok
}
peek_token_is :: proc(p: ^Parser, $T: typeid) -> bool {
_, ok := p.peek_token.(T)
return ok
}
expect_peek :: proc(p: ^Parser, $T: typeid) -> bool {
if peek_token_is(p, T) {
next_token(p)
return true
} else {
peek_error(p, T)
return false
}
}
peek_error :: proc(p: ^Parser, $T: typeid) {
msg := fmt.tprintf("expected next token to be %s, got %v instead", typeid_of(T), p.peek_token)
append(&p.errors, msg)
}
errors :: proc(p: ^Parser) -> []string {
return p.errors[:]
}
parse_program :: proc(p: ^Parser) -> ast.Program {
buf := make([dynamic]ast.Statement, context.temp_allocator)
for !cur_token_is(p, token.EOF) {
if stmt, ok := parse_statement(p); ok {
append(&buf, stmt)
}
next_token(p)
}
return ast.Program{buf[:]}
}
parse_statement :: proc(p: ^Parser) -> (stmt: ast.Statement, ok: bool) {
#partial switch t in p.cur_token {
case token.Let:
stmt, ok = parse_let_statement(p)
case token.Return:
stmt, ok = parse_return_statement(p)
case:
ok = false
}
return
}
parse_let_statement :: proc(p: ^Parser) -> (stmt: ast.Let_Statement, ok: bool) {
stmt.token = p.cur_token
if !expect_peek(p, token.Identifier) {
ok = false
return
}
stmt.name = ast.Identifier{p.cur_token, token.literal(p.cur_token)}
if !expect_peek(p, token.Equal_Sign) {
ok = false
return
}
for !cur_token_is(p, token.Semicolon) {
next_token(p)
}
ok = true
return
}
parse_return_statement :: proc(p: ^Parser) -> (stmt: ast.Return_Statement, ok: bool) {
stmt.token = p.cur_token
next_token(p)
for !cur_token_is(p, token.Semicolon) {
next_token(p)
}
ok = true
return
}
@(test)
test_let_statements :: proc(t: ^testing.T) {
input := `
let x = 5;
let y = 10;
let foobar = 838383;
`
l := lexer.new(input)
p := new(&l)
program := parse_program(&p)
defer free_all(context.allocator)
check_parse_errors(t, &p)
testing.expect_value(t, len(program.statements), 3)
expected := []string{"x", "y", "foobar"}
for identifier, index in expected {
_ = program.statements[index]
stmt := program.statements[index]
test_let_statement(t, stmt, identifier)
}
}
@(test)
test_return_statements :: proc(t: ^testing.T) {
input := `
return 5;
return 10;
return 993322;
`
l := lexer.new(input)
p := new(&l)
program := parse_program(&p)
defer free_all(context.allocator)
check_parse_errors(t, &p)
testing.expect_value(t, len(program.statements), 3)
for stmt in program.statements {
return_stmt, ok := stmt.(ast.Return_Statement)
testing.expectf(t, ok, "Type of s is not `ast.Return_Statement`. got=%T", stmt)
testing.expect_value(t, ast.token_literal(return_stmt), "return")
}
}
test_let_statement :: proc(t: ^testing.T, s: ast.Statement, name: string) {
testing.expect_value(t, ast.token_literal(s), "let")
let_stmt, ok := s.(ast.Let_Statement)
testing.expectf(t, ok, "Type of s is not `ast.Let_Statement`. got=%T", s)
testing.expect_value(t, let_stmt.name.value, name)
testing.expect_value(t, ast.token_literal(let_stmt.name), name)
}
check_parse_errors :: proc(t: ^testing.T, p: ^Parser) {
errs := errors(p)
if len(errs) == 0 {
return
}
testing.expectf(t, len(errs) == 0, "parser had %d errors", len(errs))
for msg in errs {
testing.expectf(t, false, "parser error: %q", msg)
}
testing.fail_now(t)
}
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