v/vlib/v/parser/pratt.v

// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module parser

import v.ast
import v.vet
import v.table
import v.token

pub fn (mut p Parser) expr(precedence int) ast.Expr {
	$if trace_parser ? {
		tok_pos := p.tok.position()
		eprintln('parsing file: ${p.file_name:-30} | tok.kind: ${p.tok.kind:-10} | tok.lit: ${p.tok.lit:-10} | tok_pos: ${tok_pos.str():-45} | expr($precedence)')
	}
	// println('\n\nparser.expr()')
	mut node := ast.Expr{}
	is_stmt_ident := p.is_stmt_ident
	p.is_stmt_ident = false
	if !p.pref.is_fmt {
		p.eat_comments({})
	}
	// Prefix
	match p.tok.kind {
		.key_mut, .key_shared, .key_atomic, .key_static {
			node = p.parse_ident(table.Language.v)
			p.is_stmt_ident = is_stmt_ident
		}
		.name {
			if p.tok.lit == 'sql' && p.peek_tok.kind == .name {
				p.inside_match = true // reuse the same var for perf instead of inside_sql TODO rename
				node = p.sql_expr()
				p.inside_match = false
			} else {
				if p.inside_if && p.is_generic_name() {
					// $if T is string {}
					p.expecting_type = true
				}
				node = p.name_expr()
				p.is_stmt_ident = is_stmt_ident
			}
		}
		.string {
			node = p.string_expr()
		}
		.comment {
			node = p.comment()
		}
		.dot {
			// .enum_val
			node = p.enum_val()
		}
		.at {
			node = p.at()
		}
		.dollar {
			match p.peek_tok.kind {
				.name {
					return p.comp_call()
				}
				.key_if {
					return p.if_expr(true)
				}
				else {
					p.error_with_pos('unexpected `$`', p.peek_tok.position())
					return ast.Expr{}
				}
			}
		}
		.chartoken {
			node = ast.CharLiteral{
				val: p.tok.lit
				pos: p.tok.position()
			}
			p.next()
		}
		.amp, .mul, .not, .bit_not, .arrow {
			// -1, -a, !x, &x, ~x, <-a
			node = p.prefix_expr()
		}
		.minus {
			if p.peek_tok.kind == .number {
				node = p.parse_number_literal()
			} else {
				node = p.prefix_expr()
			}
		}
		.key_go {
			stmt := p.stmt(false)
			go_stmt := stmt as ast.GoStmt
			node = ast.GoExpr{
				go_stmt: go_stmt
				pos: go_stmt.pos
			}
		}
		.key_true, .key_false {
			node = ast.BoolLiteral{
				val: p.tok.kind == .key_true
				pos: p.tok.position()
			}
			p.next()
		}
		.key_match {
			node = p.match_expr()
		}
		.key_select {
			node = p.select_expr()
		}
		.number {
			node = p.parse_number_literal()
		}
		.lpar {
			mut pos := p.tok.position()
			p.check(.lpar)
			node = p.expr(0)
			p.check(.rpar)
			node = ast.ParExpr{
				expr: node
				pos: pos.extend(p.prev_tok.position())
			}
		}
		.key_if {
			node = p.if_expr(false)
		}
		.key_unsafe {
			// unsafe {
			mut pos := p.tok.position()
			p.next()
			if p.inside_unsafe {
				p.error_with_pos('already inside `unsafe` block', pos)
				return ast.Expr{}
			}
			p.inside_unsafe = true
			p.check(.lcbr)
			e := p.expr(0)
			p.check(.rcbr)
			pos.update_last_line(p.prev_tok.line_nr)
			node = ast.UnsafeExpr{
				expr: e
				pos: pos
			}
			p.inside_unsafe = false
		}
		.key_lock, .key_rlock {
			node = p.lock_expr()
		}
		.lsbr {
			if p.expecting_type {
				// parse json.decode type (`json.decode([]User, s)`)
				node = p.name_expr()
			} else if p.is_amp && p.peek_tok.kind == .rsbr && p.peek_tok3.kind != .lcbr {
				pos := p.tok.position()
				typ := p.parse_type().to_ptr()
				p.check(.lpar)
				expr := p.expr(0)
				p.check(.rpar)
				node = ast.CastExpr{
					typ: typ
					expr: expr
					pos: pos
				}
			} else {
				node = p.array_init()
			}
		}
		.key_none {
			pos := p.tok.position()
			p.next()
			node = ast.None{
				pos: pos
			}
		}
		.key_sizeof {
			p.next() // sizeof
			p.check(.lpar)
			pos := p.tok.position()
			is_known_var := p.mark_var_as_used(p.tok.lit)
			// assume mod. prefix leads to a type
			if is_known_var || !(p.known_import(p.tok.lit) || p.tok.kind.is_start_of_type()) {
				expr := p.expr(0)
				node = ast.SizeOf{
					is_type: false
					expr: expr
					pos: pos
				}
			} else {
				p.register_used_import(p.tok.lit)
				save_expr_mod := p.expr_mod
				p.expr_mod = ''
				sizeof_type := p.parse_type()
				p.expr_mod = save_expr_mod
				node = ast.SizeOf{
					is_type: true
					typ: sizeof_type
					pos: pos
				}
			}
			p.check(.rpar)
		}
		.key_typeof {
			spos := p.tok.position()
			p.next()
			p.check(.lpar)
			expr := p.expr(0)
			p.check(.rpar)
			if p.tok.kind != .dot && p.tok.line_nr == p.prev_tok.line_nr {
				p.warn_with_pos('use e.g. `typeof(expr).name` or `sum_type_instance.type_name()` instead',
					spos)
			}
			node = ast.TypeOf{
				expr: expr
				pos: spos.extend(p.tok.position())
			}
		}
		.key_offsetof {
			pos := p.tok.position()
			p.next() // __offsetof
			p.check(.lpar)
			st := p.parse_type()
			p.check(.comma)
			if p.tok.kind != .name {
				p.error_with_pos('unexpected `$p.tok.lit`, expecting struct field', p.tok.position())
				return ast.Expr{}
			}
			field := p.tok.lit
			p.next()
			p.check(.rpar)
			node = ast.OffsetOf{
				struct_type: st
				field: field
				pos: pos
			}
		}
		.key_likely, .key_unlikely {
			is_likely := p.tok.kind == .key_likely
			p.next()
			p.check(.lpar)
			lpos := p.tok.position()
			expr := p.expr(0)
			p.check(.rpar)
			node = ast.Likely{
				expr: expr
				pos: lpos
				is_likely: is_likely
			}
		}
		.lcbr {
			// Map `{"age": 20}` or `{ x | foo:bar, a:10 }`
			p.next()
			if p.tok.kind in [.chartoken, .number, .string] {
				// TODO deprecate
				node = p.map_init()
			} else {
				// it should be a struct
				if p.tok.kind == .name && p.peek_tok.kind == .pipe {
					p.warn_with_pos('use e.g. `...struct_var` instead', p.peek_tok.position())
					node = p.assoc()
				} else if (p.tok.kind == .name && p.peek_tok.kind == .colon)
					|| p.tok.kind in [.rcbr, .comment, .ellipsis] {
					node = p.struct_init(true) // short_syntax: true
				} else if p.tok.kind == .name {
					p.next()
					p.error_with_pos('unexpected $p.tok, expecting `:` after struct field name',
						p.tok.position())
					return ast.Expr{}
				} else {
					p.error_with_pos('unexpected $p.tok, expecting struct field name',
						p.tok.position())
					return ast.Expr{}
				}
			}
			p.check(.rcbr)
		}
		.key_fn {
			if p.expecting_type {
				// Anonymous function type
				start_pos := p.tok.position()
				return ast.Type{
					typ: p.parse_type()
					pos: start_pos.extend(p.prev_tok.position())
				}
			} else {
				// Anonymous function
				node = p.anon_fn()
				// its a call
				// NOTE: this could be moved to just before the pratt loop
				// then anything can be a call, eg. `index[2]()` or `struct.field()`
				// but this would take a bit of modification
				if p.tok.kind == .lpar {
					p.next()
					pos := p.tok.position()
					args := p.call_args()
					p.check(.rpar)
					node = ast.CallExpr{
						name: 'anon'
						left: node
						args: args
						pos: pos
						scope: p.scope
					}
				}
				return node
			}
		}
		else {
			if p.tok.kind != .eof {
				// eof should be handled where it happens
				p.error_with_pos('invalid expression: unexpected $p.tok', p.tok.position())
				return ast.Expr{}
			}
		}
	}
	return p.expr_with_left(node, precedence, is_stmt_ident)
}

pub fn (mut p Parser) expr_with_left(left ast.Expr, precedence int, is_stmt_ident bool) ast.Expr {
	mut node := left
	// Infix
	for precedence < p.tok.precedence() {
		if p.tok.kind == .dot {
			node = p.dot_expr(node)
			if p.name_error {
				return node
			}
			p.is_stmt_ident = is_stmt_ident
		} else if p.tok.kind == .lsbr && (p.inside_fn || p.tok.line_nr == p.prev_tok.line_nr) {
			node = p.index_expr(node)
			p.is_stmt_ident = is_stmt_ident
			if p.tok.kind == .lpar && p.tok.line_nr == p.prev_tok.line_nr && node is ast.IndexExpr {
				p.next()
				pos := p.tok.position()
				args := p.call_args()
				p.check(.rpar)
				node = ast.CallExpr{
					left: node
					args: args
					pos: pos
					scope: p.scope
				}
				p.is_stmt_ident = is_stmt_ident
			}
		} else if p.tok.kind == .key_as {
			// sum type as cast `x := SumType as Variant`
			pos := p.tok.position()
			p.next()
			typ := p.parse_type()
			node = ast.AsCast{
				expr: node
				typ: typ
				pos: pos
			}
		} else if p.tok.kind == .left_shift && p.is_stmt_ident {
			// arr << elem
			tok := p.tok
			mut pos := tok.position()
			p.next()
			right := p.expr(precedence - 1)
			pos.update_last_line(p.prev_tok.line_nr)
			if mut node is ast.IndexExpr {
				node.recursive_mapset_is_setter(true)
			}
			node = ast.InfixExpr{
				left: node
				right: right
				op: tok.kind
				pos: pos
			}
		} else if p.tok.kind.is_infix() {
			if p.tok.kind.is_prefix() && p.tok.line_nr != p.prev_tok.line_nr {
				// return early for deref assign `*x = 2` goes to prefix expr
				if p.tok.kind == .mul && p.peek_tok2.kind == .assign {
					return node
				}
				// added 10/2020: LATER this will be parsed as PrefixExpr instead
				p.warn_with_pos('move infix `$p.tok.kind` operator before new line (if infix intended) or use brackets for a prefix expression',
					p.tok.position())
			}
			// continue on infix expr
			node = p.infix_expr(node)
			// return early `if bar is SumType as b {`
			if p.tok.kind == .key_as && p.inside_if {
				return node
			}
		} else if p.tok.kind in [.inc, .dec] || (p.tok.kind == .question && p.inside_ct_if_expr) {
			// Postfix
			// detect `f(x++)`, `a[x++]`
			if p.peek_tok.kind in [.rpar, .rsbr] && p.mod !in ['builtin', 'regex', 'strconv'] { // temp
				p.warn_with_pos('`$p.tok.kind` operator can only be used as a statement',
					p.peek_tok.position())
			}
			if p.tok.kind in [.inc, .dec] && p.prev_tok.line_nr != p.tok.line_nr {
				p.error_with_pos('$p.tok must be on the same line as the previous token',
					p.tok.position())
			}
			if mut node is ast.IndexExpr {
				node.recursive_mapset_is_setter(true)
			}
			node = ast.PostfixExpr{
				op: p.tok.kind
				expr: node
				pos: p.tok.position()
			}
			p.next()
			// return node // TODO bring back, only allow ++/-- in exprs in translated code
		} else {
			return node
		}
	}
	return node
}

fn (mut p Parser) infix_expr(left ast.Expr) ast.Expr {
	op := p.tok.kind
	if op == .arrow {
		p.or_is_handled = true
		p.register_auto_import('sync')
	}
	precedence := p.tok.precedence()
	mut pos := p.tok.position()
	p.next()
	mut right := ast.Expr{}
	prev_expecting_type := p.expecting_type
	if op in [.key_is, .not_is] {
		p.expecting_type = true
	}
	right = p.expr(precedence)
	p.expecting_type = prev_expecting_type
	if p.pref.is_vet && op in [.key_in, .not_in] && right is ast.ArrayInit
		&& (right as ast.ArrayInit).exprs.len == 1 {
		p.vet_error('Use `var == value` instead of `var in [value]`', pos.line_nr, vet.FixKind.vfmt)
	}
	mut or_stmts := []ast.Stmt{}
	mut or_kind := ast.OrKind.absent
	mut or_pos := p.tok.position()
	// allow `x := <-ch or {...}` to handle closed channel
	if op == .arrow {
		if p.tok.kind == .key_orelse {
			p.next()
			p.open_scope()
			p.scope.register(ast.Var{
				name: 'errcode'
				typ: table.int_type
				pos: p.tok.position()
				is_used: true
			})
			p.scope.register(ast.Var{
				name: 'err'
				typ: table.string_type
				pos: p.tok.position()
				is_used: true
			})
			or_kind = .block
			or_stmts = p.parse_block_no_scope(false)
			or_pos = or_pos.extend(p.prev_tok.position())
			p.close_scope()
		}
		if p.tok.kind == .question {
			p.next()
			or_kind = .propagate
		}
		p.or_is_handled = false
	}
	pos.update_last_line(p.prev_tok.line_nr)
	return ast.InfixExpr{
		left: left
		right: right
		op: op
		pos: pos
		or_block: ast.OrExpr{
			stmts: or_stmts
			kind: or_kind
			pos: or_pos
		}
	}
}

fn (mut p Parser) prefix_expr() ast.PrefixExpr {
	mut pos := p.tok.position()
	op := p.tok.kind
	if op == .amp {
		p.is_amp = true
	}
	if op == .arrow {
		p.or_is_handled = true
		p.register_auto_import('sync')
	}
	// if op == .mul && !p.inside_unsafe {
	// p.warn('unsafe')
	// }
	p.next()
	mut right := if op == .minus {
		p.expr(int(token.Precedence.call))
	} else {
		p.expr(int(token.Precedence.prefix))
	}
	p.is_amp = false
	if mut right is ast.CastExpr {
		right.in_prexpr = true
	}
	mut or_stmts := []ast.Stmt{}
	mut or_kind := ast.OrKind.absent
	mut or_pos := p.tok.position()
	// allow `x := <-ch or {...}` to handle closed channel
	if op == .arrow {
		if p.tok.kind == .key_orelse {
			p.next()
			p.open_scope()
			p.scope.register(ast.Var{
				name: 'errcode'
				typ: table.int_type
				pos: p.tok.position()
				is_used: true
			})
			p.scope.register(ast.Var{
				name: 'err'
				typ: table.string_type
				pos: p.tok.position()
				is_used: true
			})
			or_kind = .block
			or_stmts = p.parse_block_no_scope(false)
			or_pos = or_pos.extend(p.prev_tok.position())
			p.close_scope()
		}
		if p.tok.kind == .question {
			p.next()
			or_kind = .propagate
		}
		p.or_is_handled = false
	}
	pos.update_last_line(p.prev_tok.line_nr)
	return ast.PrefixExpr{
		op: op
		right: right
		pos: pos
		or_block: ast.OrExpr{
			stmts: or_stmts
			kind: or_kind
			pos: or_pos
		}
	}
}