feat: add initial support for import, provide minimal fmt (#6)

The `import` statement is now parsed. It only provides minimal
support for the `fmt` package (only `Println` symbol is defined).

This should be sufficient to pass a few tests.

Full support of package namespaces, source and binary imports will be
supported later, based on this work.

1 files changed, 59 insertions, 0 deletions

diff --git a/parser/decl.go b/parser/decl.go
index d794131..7638b75 100644
--- a/parser/decl.go
+++ b/parser/decl.go
@@ -2,8 +2,10 @@ package parser
 
 import (
 	"errors"
+	"fmt"
 	"go/constant"
 	"go/token"
+	"path"
 	"strings"
 
 	"github.com/mvertes/parscan/lang"
@@ -189,6 +191,63 @@ var gotok = map[lang.TokenId]token.Token{
 	lang.Not:          token.NOT,
 }
 
+func (p *Parser) ParseImport(in Tokens) (out Tokens, err error) {
+	if p.fname != "" {
+		return out, errors.New("unexpected import")
+	}
+	if len(in) < 2 {
+		return out, errors.New("missing expression")
+	}
+	if in[1].Id != lang.ParenBlock {
+		return p.parseImportLine(in[1:])
+	}
+	if in, err = p.Scan(in[1].Block(), false); err != nil {
+		return out, err
+	}
+	for _, li := range in.Split(lang.Semicolon) {
+		ot, err := p.parseImportLine(li)
+		if err != nil {
+			return out, err
+		}
+		out = append(out, ot...)
+	}
+	return out, err
+}
+
+func (p *Parser) parseImportLine(in Tokens) (out Tokens, err error) {
+	l := len(in)
+	if l != 1 && l != 2 {
+		return out, errors.New("invalid number of arguments")
+	}
+	if in[l-1].Id != lang.String {
+		return out, fmt.Errorf("invalid argument %v", in[0])
+	}
+	pp := in[l-1].Block()
+	pkg, ok := packages[pp]
+	if !ok {
+		// TODO: try to import source package from here.
+		return out, fmt.Errorf("package not found: %s", pp)
+	}
+	n := in[0].Str
+	if l == 1 {
+		// Derive package name from package path.
+		d, f := path.Split(pp)
+		n = f
+		if ok, _ := path.Match(f, "v[0-9]*"); d != "" && ok {
+			n = path.Base(d)
+		}
+	}
+	if n == "." {
+		// Import package symbols in the current scope.
+		for k, v := range pkg {
+			p.symbols[k] = &symbol{index: unsetAddr, pkgPath: pp, value: v}
+		}
+	} else {
+		p.symbols[n] = &symbol{kind: symPkg, pkgPath: pp, index: unsetAddr}
+	}
+	return out, err
+}
+
 func (p *Parser) ParseType(in Tokens) (out Tokens, err error) {
 	if len(in) < 2 {
 		return out, MissingTypeErr