chore: add missing tests for var-declarations, fix any/interface{} ty…

…pe issue

rule/var_declarations.go

@@ -85,7 +85,7 @@ func (w *lintVarDeclarations) Visit(node ast.Node) ast.Visitor {
 		// If the RHS is a isZero value, suggest dropping it.
 		isZero := false
 		if lit, ok := rhs.(*ast.BasicLit); ok {
-			isZero = zeroLiteral[lit.Value]
+			isZero = isZeroValue(lit.Value, v.Type)
 		} else if isIdent(rhs, "nil") {
 			isZero = true
 		}
@@ -142,3 +142,14 @@ func validType(t types.Type) bool {
 		t != types.Typ[types.Invalid] &&
 		!strings.Contains(t.String(), "invalid type") // good but not foolproof
 }
+
+func isZeroValue(litValue string, typ ast.Expr) bool {
+	switch val := typ.(type) {
+	case *ast.Ident:
+		return val.Name == "any" && litValue == "nil"
+	case *ast.InterfaceType:
+		return litValue == "nil"
+	}
+
+	return zeroLiteral[litValue]
+}

test/var_declarations_test.go

@@ -0,0 +1,13 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/lint"
+	"github.com/mgechev/revive/rule"
+)
+
+func TestVarDeclarations(t *testing.T) {
+	testRule(t, "var_declarations_type_inference", &rule.VarDeclarationsRule{}, &lint.RuleConfig{})
+	testRule(t, "var_declarations_zero_value", &rule.VarDeclarationsRule{}, &lint.RuleConfig{})
+}

testdata/var_declarations_type_inference.go

@@ -0,0 +1,6 @@
+package fixtures
+
+func typeInferenceExample() {
+	var x int = 42 // MATCH /should omit type int from declaration of var x; it will be inferred from the right-hand side/
+	var y = 42     // No warning, type is inferred
+}

testdata/var_declarations_zero_value.go

@@ -0,0 +1,9 @@
+package fixtures
+
+func zeroValueExample() {
+	var y int                // No warning, zero value is implicit
+	var z1 any = 0           // No warning, zero value for any is nil
+	var z2 any = nil         // MATCH /should drop = nil from declaration of var z2; it is the zero value/
+	var z3 interface{} = 0   // No warning, zero value for any is nil
+	var z4 interface{} = nil // MATCH /should drop = nil from declaration of var z4; it is the zero value/
+}