121 lines
3.1 KiB
Go
Vendored
121 lines
3.1 KiB
Go
Vendored
package rule
|
|
|
|
import (
|
|
"fmt"
|
|
"go/ast"
|
|
"go/token"
|
|
"go/types"
|
|
|
|
"github.com/mgechev/revive/lint"
|
|
)
|
|
|
|
// VarDeclarationsRule lints given else constructs.
|
|
type VarDeclarationsRule struct{}
|
|
|
|
// Apply applies the rule to given file.
|
|
func (r *VarDeclarationsRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
|
|
var failures []lint.Failure
|
|
|
|
fileAst := file.AST
|
|
walker := &lintVarDeclarations{
|
|
file: file,
|
|
fileAst: fileAst,
|
|
onFailure: func(failure lint.Failure) {
|
|
failures = append(failures, failure)
|
|
},
|
|
}
|
|
|
|
file.Pkg.TypeCheck()
|
|
ast.Walk(walker, fileAst)
|
|
|
|
return failures
|
|
}
|
|
|
|
// Name returns the rule name.
|
|
func (r *VarDeclarationsRule) Name() string {
|
|
return "var-declaration"
|
|
}
|
|
|
|
type lintVarDeclarations struct {
|
|
fileAst *ast.File
|
|
file *lint.File
|
|
lastGen *ast.GenDecl
|
|
onFailure func(lint.Failure)
|
|
}
|
|
|
|
func (w *lintVarDeclarations) Visit(node ast.Node) ast.Visitor {
|
|
switch v := node.(type) {
|
|
case *ast.GenDecl:
|
|
if v.Tok != token.CONST && v.Tok != token.VAR {
|
|
return nil
|
|
}
|
|
w.lastGen = v
|
|
return w
|
|
case *ast.ValueSpec:
|
|
if w.lastGen.Tok == token.CONST {
|
|
return nil
|
|
}
|
|
if len(v.Names) > 1 || v.Type == nil || len(v.Values) == 0 {
|
|
return nil
|
|
}
|
|
rhs := v.Values[0]
|
|
// An underscore var appears in a common idiom for compile-time interface satisfaction,
|
|
// as in "var _ Interface = (*Concrete)(nil)".
|
|
if isIdent(v.Names[0], "_") {
|
|
return nil
|
|
}
|
|
// If the RHS is a zero value, suggest dropping it.
|
|
zero := false
|
|
if lit, ok := rhs.(*ast.BasicLit); ok {
|
|
zero = zeroLiteral[lit.Value]
|
|
} else if isIdent(rhs, "nil") {
|
|
zero = true
|
|
}
|
|
if zero {
|
|
w.onFailure(lint.Failure{
|
|
Confidence: 0.9,
|
|
Node: rhs,
|
|
Category: "zero-value",
|
|
Failure: fmt.Sprintf("should drop = %s from declaration of var %s; it is the zero value", w.file.Render(rhs), v.Names[0]),
|
|
})
|
|
return nil
|
|
}
|
|
lhsTyp := w.file.Pkg.TypeOf(v.Type)
|
|
rhsTyp := w.file.Pkg.TypeOf(rhs)
|
|
|
|
if !validType(lhsTyp) || !validType(rhsTyp) {
|
|
// Type checking failed (often due to missing imports).
|
|
return nil
|
|
}
|
|
|
|
if !types.Identical(lhsTyp, rhsTyp) {
|
|
// Assignment to a different type is not redundant.
|
|
return nil
|
|
}
|
|
|
|
// The next three conditions are for suppressing the warning in situations
|
|
// where we were unable to typecheck.
|
|
|
|
// If the LHS type is an interface, don't warn, since it is probably a
|
|
// concrete type on the RHS. Note that our feeble lexical check here
|
|
// will only pick up interface{} and other literal interface types;
|
|
// that covers most of the cases we care to exclude right now.
|
|
if _, ok := v.Type.(*ast.InterfaceType); ok {
|
|
return nil
|
|
}
|
|
// If the RHS is an untyped const, only warn if the LHS type is its default type.
|
|
if defType, ok := w.file.IsUntypedConst(rhs); ok && !isIdent(v.Type, defType) {
|
|
return nil
|
|
}
|
|
|
|
w.onFailure(lint.Failure{
|
|
Category: "type-inference",
|
|
Confidence: 0.8,
|
|
Node: v.Type,
|
|
Failure: fmt.Sprintf("should omit type %s from declaration of var %s; it will be inferred from the right-hand side", w.file.Render(v.Type), v.Names[0]),
|
|
})
|
|
return nil
|
|
}
|
|
return w
|
|
}
|