chore: add linters and some lint fixes (#8)

* chore: add linters and some lint fixes

Configure some golangci-lint linters to get the code quality right.
Apply the first fixes.

Next step will be to add github actions to run lint and tests in
github CI.

* chore: more lint, fixed comments and variable names. no semantic change.

* chore: add Makefile

This makefile is intended to be used as a local substitute to github
actions.

1 files changed, 41 insertions, 23 deletions

diff --git a/lang/token.go b/lang/token.go
index 613f2c6..7ad7bf1 100644
--- a/lang/token.go
+++ b/lang/token.go
@@ -1,23 +1,25 @@
 package lang
 
-//go:generate stringer -type=TokenId
+//go:generate stringer -type=Token
 
-type TokenId int
+// Token represents a lexical token.
+type Token int
 
+// All known tokens for the set of supported languages.
 const (
-	Illegal TokenId = iota
+	Illegal Token = iota
 	Comment
 	Ident
 
-	// Literal values
+	// Literal values.
 	Char
 	Float
 	Imag
 	Int
 	String
 
-	// Binary operators (except indicated)
-	// Arithmetic and bitwise binary operators
+	// Binary operators (except indicated).
+	// Arithmetic and bitwise binary operators.
 	Add    // +
 	Sub    // -
 	Mul    // *
@@ -31,7 +33,7 @@ const (
 	AndNot // &^
 	Period // .
 
-	// Binary operators returning a boolean
+	// Binary operators returning a boolean.
 	Equal        // ==
 	Greater      // >
 	GreaterEqual // >=
@@ -41,7 +43,7 @@ const (
 	Lor          // ||
 	NotEqual     // !=
 
-	// Assigment operators (arithmetic and bitwise)
+	// Assigment operators (arithmetic and bitwise).
 	Define       // :=
 	Assign       // =
 	AddAssign    // +=
@@ -58,7 +60,7 @@ const (
 	Inc          // ++
 	Dec          // --
 
-	// Unary operations
+	// Unary operations.
 	Plus     // unary +
 	Minus    // unary -
 	Addr     // unary &
@@ -69,17 +71,17 @@ const (
 	Not      // unary !
 	Tilde    // unary ~ (underlying type)
 
-	// Separators (punctuation)
+	// Separators (punctuation).
 	Comma     // ,
 	Semicolon // ;
 	Colon     // :
 
-	// Block tokens
+	// Block tokens.
 	ParenBlock   // (..)
 	BracketBlock // [..]
 	BraceBlock   // {..}
 
-	// Reserved keywords
+	// Reserved keywords.
 	Break
 	Case
 	Chan
@@ -106,7 +108,7 @@ const (
 	Type
 	Var
 
-	// Internal virtual machine tokens (no corresponding keyword)
+	// Internal virtual machine tokens (no corresponding keyword).
 	Call
 	CallX
 	EqualSet
@@ -119,8 +121,9 @@ const (
 	New
 )
 
-// TODO: define UnaryOp per language
-var UnaryOp = map[TokenId]TokenId{
+// UnaryOp contains the set of unary operators.
+// TODO: define UnaryOp per language.
+var UnaryOp = map[Token]Token{
 	Add:   Plus,    // +
 	And:   Addr,    // &
 	Not:   Not,     // !
@@ -130,11 +133,26 @@ var UnaryOp = map[TokenId]TokenId{
 	Xor:   BitComp, // ^
 }
 
-func (t TokenId) IsKeyword() bool   { return t >= Break && t <= Var }
-func (t TokenId) IsLiteral() bool   { return t >= Char && t <= String }
-func (t TokenId) IsOperator() bool  { return t >= Add && t <= Tilde }
-func (t TokenId) IsBlock() bool     { return t >= ParenBlock && t <= BraceBlock }
-func (t TokenId) IsBoolOp() bool    { return t >= Equal && t <= NotEqual || t == Not }
-func (t TokenId) IsBinaryOp() bool  { return t >= Add && t <= NotEqual }
-func (t TokenId) IsUnaryOp() bool   { return t >= Plus && t <= Tilde }
-func (t TokenId) IsLogicalOp() bool { return t == Land || t == Lor }
+// IsKeyword returns true if t is a keyword.
+func (t Token) IsKeyword() bool { return t >= Break && t <= Var }
+
+// IsLiteral returns true if t is a literal value.
+func (t Token) IsLiteral() bool { return t >= Char && t <= String }
+
+// IsOperator returns true if t is an operator.
+func (t Token) IsOperator() bool { return t >= Add && t <= Tilde }
+
+// IsBlock returns true if t is a block kind of token.
+func (t Token) IsBlock() bool { return t >= ParenBlock && t <= BraceBlock }
+
+// IsBoolOp returns true if t is boolean operator.
+func (t Token) IsBoolOp() bool { return t >= Equal && t <= NotEqual || t == Not }
+
+// IsBinaryOp returns true if t is a binary operator (takes 2 operands).
+func (t Token) IsBinaryOp() bool { return t >= Add && t <= NotEqual }
+
+// IsUnaryOp returns true if t is an unary operator (takes 1 operand).
+func (t Token) IsUnaryOp() bool { return t >= Plus && t <= Tilde }
+
+// IsLogicalOp returns true if t is a logical operator.
+func (t Token) IsLogicalOp() bool { return t == Land || t == Lor }