doc: improve comments, pass lint

Also improve the setup of golangci-lint.

9 files changed, 30 insertions, 60 deletions

diff --git a/.golangci.yaml b/.golangci.yaml
index bc1fbb6..34d9d92 100644
--- a/.golangci.yaml
+++ b/.golangci.yaml
@@ -4,30 +4,20 @@ linters:
     - gocritic
     - godot
     - gosec
+    - ineffassign
     - misspell
+    - modernize
     - perfsprint
     - prealloc
     - predeclared
     - reassign
     - revive
+    - staticcheck
     - unconvert
+    - unused
   exclusions:
-    generated: lax
     presets:
       - common-false-positives
-      - legacy
-      - std-error-handling
-      - comments
-    paths:
-      - third_party$
-      - builtin$
-      - examples$
 formatters:
   enable:
     - gofumpt
-  exclusions:
-    generated: lax
-    paths:
-      - third_party$
-      - builtin$
-      - examples$
diff --git a/compiler/compiler.go b/compiler/compiler.go
index f7c8a12..679a886 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -1,3 +1,4 @@
+// Package compiler implements a compiler targeting the vm.
 package compiler
 
 import (
diff --git a/interpreter/interpreter.go b/interpreter/interpreter.go
index 62b593b..032a66f 100644
--- a/interpreter/interpreter.go
+++ b/interpreter/interpreter.go
@@ -1,3 +1,4 @@
+// Package interpreter implements an interpreter.
 package interpreter
 
 import (
diff --git a/interpreter/interpreter_test.go b/interpreter/interpreter_test.go
index 71c7dd1..e48efdb 100644
--- a/interpreter/interpreter_test.go
+++ b/interpreter/interpreter_test.go
@@ -42,7 +42,6 @@ func gen(test etest) func(*testing.T) {
 
 func run(t *testing.T, tests []etest) {
 	for _, test := range tests {
-		test := test
 		t.Run("", gen(test))
 	}
 }
diff --git a/main.go b/main.go
index b0ca700..0e95bd4 100644
--- a/main.go
+++ b/main.go
@@ -1,12 +1,11 @@
+// The parscan command interprets programs.
 package main
 
 import (
 	"flag"
 	"fmt"
-	"io"
 	"log"
 	"os"
-	"strings"
 
 	"github.com/mvertes/parscan/interpreter"
 	"github.com/mvertes/parscan/lang/golang"
@@ -19,7 +18,7 @@ func main() {
 	}
 }
 
-func run(arg []string) (err error) {
+func run(arg []string) error {
 	var str string
 	rflag := flag.NewFlagSet("run", flag.ContinueOnError)
 	rflag.Usage = func() {
@@ -28,46 +27,26 @@ func run(arg []string) (err error) {
 		rflag.PrintDefaults()
 	}
 	rflag.StringVar(&str, "e", "", "string to eval")
-	if err = rflag.Parse(arg); err != nil {
+	if err := rflag.Parse(arg); err != nil {
 		return err
 	}
 	args := rflag.Args()
 
 	interp := interpreter.NewInterpreter(golang.GoSpec)
-
-	var in io.Reader
 	if str != "" {
-		in = strings.NewReader(str)
-	} else {
-		in = os.Stdin
-	}
-	if len(args) > 0 {
-		if in, err = os.Open(arg[0]); err != nil {
-			return err
-		}
-		if i2, ok := in.(io.ReadCloser); ok {
-			defer i2.Close()
-		}
+		return evalStr(interp, str)
 	}
-
-	if isatty(in) {
-		return interp.Repl(in)
+	if len(args) == 0 {
+		return interp.Repl(os.Stdin)
 	}
-
-	buf, err := io.ReadAll(in)
+	buf, err := os.ReadFile(arg[0])
 	if err != nil {
 		return err
 	}
-	_, err = interp.Eval(string(buf))
-	return err
+	return evalStr(interp, string(buf))
 }
 
-// isatty returns true if the input stream is a tty (i.e. a character device).
-func isatty(in io.Reader) bool {
-	s, ok := in.(interface{ Stat() (os.FileInfo, error) })
-	if !ok {
-		return false
-	}
-	stat, err := s.Stat()
-	return err == nil && stat.Mode()&os.ModeCharDevice != 0
+func evalStr(i *interpreter.Interp, s string) error {
+	_, err := i.Eval(s)
+	return err
 }
diff --git a/parser/package.go b/parser/package.go
index 67e2867..d1e326f 100644
--- a/parser/package.go
+++ b/parser/package.go
@@ -6,6 +6,7 @@ import (
 	"github.com/mvertes/parscan/vm"
 )
 
+// Packages contains binary package references.
 var Packages = map[string]map[string]vm.Value{
 	"fmt": fmtPkg,
 }
diff --git a/parser/symbol.go b/parser/symbol.go
index 3aba4e5..3ad8fda 100644
--- a/parser/symbol.go
+++ b/parser/symbol.go
@@ -8,8 +8,10 @@ import (
 	"github.com/mvertes/parscan/vm"
 )
 
+// SymKind represents the symbol kind.
 type SymKind int
 
+// Symbol kinds.
 const (
 	SymValue SymKind = iota // a value defined in the runtime
 	SymType                 // a type
@@ -22,8 +24,10 @@ const (
 
 //go:generate stringer -type=SymKind
 
+// UnsetAddr denotes an unset symbol index (vs 0).
 const UnsetAddr = -65535
 
+// Symbol structure used in parser and compiler.
 type Symbol struct {
 	Kind    SymKind
 	Index   int            // address of symbol in frame
@@ -35,6 +39,7 @@ type Symbol struct {
 	Used    bool           //
 }
 
+// SymbolType returns the VM type of a symbol.
 func SymbolType(s *Symbol) *vm.Type {
 	if s.Type != nil {
 		return s.Type
@@ -42,11 +47,7 @@ func SymbolType(s *Symbol) *vm.Type {
 	return vm.TypeOf(s.Value)
 }
 
-// AddSym add a new named value at memory position i in the parser symbol table.
-// func (p *Parser) AddSym(i int, name string, v vm.Value) {
-// 	p.addSym(i, name, v, SymValue, nil, false)
-// }
-
+// AddSymbol adds a new named value at memory position i in the parser symbol table.
 func (p *Parser) AddSymbol(i int, name string, v vm.Value, k SymKind, t *vm.Type, local bool) {
 	name = strings.TrimPrefix(name, "/")
 	p.Symbols[name] = &Symbol{Kind: k, Index: i, Local: local, Value: v, Type: t}
diff --git a/scanner/scan.go b/scanner/scan.go
index b5e9962..edd8b1c 100644
--- a/scanner/scan.go
+++ b/scanner/scan.go
@@ -155,10 +155,7 @@ func (sc *Scanner) Scan(src string, semiEOF bool) (tokens []Token, err error) {
 func loc(s string, p int) string {
 	s = s[:p]
 	l := strings.Count(s, "\n")
-	li := strings.LastIndex(s, "\n")
-	if li < 0 {
-		li = 0
-	}
+	li := max(strings.LastIndex(s, "\n"), 0)
 	return fmt.Sprintf("%d:%d", 1+l, 1+len(s)-li)
 }
 
diff --git a/vm/vm.go b/vm/vm.go
index f981415..18207f7 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -11,10 +11,8 @@ import (
 
 const debug = true
 
-type (
-	Op  int // Op is a VM opcode (bytecode instruction).
-	Pos int // Pos is the source code position of instruction
-)
+// Op is a VM opcode (bytecode instruction).
+type Op int
 
 //go:generate stringer -type=Op
 
@@ -58,6 +56,9 @@ const (
 	Swap                   // --
 )
 
+// Pos is the source code position of instruction.
+type Pos int
+
 // Instruction represents a virtual machine bytecode instruction.
 type Instruction struct {
 	Pos       // position in source