waiig15/parser/parser_expression.go

package parser

import (
	"fmt"

	"code.osinet.fr/fgm/waiig15/ast"
	"code.osinet.fr/fgm/waiig15/token"
)

func (p *Parser) noPrefixParseFnError(t token.TokenType) {
	msg := fmt.Sprintf("no prefix parse function for %s found", t)
	p.errors = append(p.errors, msg)
}

func (p *Parser) parseExpression(precedence int) ast.Expression {
	defer untrace(trace("parseExpression"))
	prefix := p.prefixParseFns[p.curToken.Type]
	if prefix == nil {
		p.noPrefixParseFnError(p.curToken.Type)
		return nil
	}

	leftExp := prefix()

	for !p.peekTokenIs(token.SEMICOLON) && precedence < p.peekPrecedence() {
		infix := p.infixParseFns[p.peekToken.Type]
		if infix == nil {
			return leftExp
		}

		p.nextToken()
		leftExp = infix(leftExp)
	}

	return leftExp
}

func (p *Parser) parseExpressionStatement() *ast.ExpressionStatement {
	defer untrace(trace("parseExpressionStatement"))
	stmt := &ast.ExpressionStatement{
		Token: p.curToken,
	}

	stmt.Expression = p.parseExpression(LOWEST)

	// Semicolons are optional to help use REPL input.
	if p.peekTokenIs(token.SEMICOLON) {
		p.nextToken()
	}

	return stmt
}