Add IfSwitchExpressionRule for enforcing if and switch statements. In…

Source/SwiftLintBuiltInRules/Rules/Style/IfSwitchExpressionRule.swift

@@ -0,0 +1,30 @@
+import Foundation
+import SwiftSyntax
+import SwiftLintCore
+
+
+@SwiftSyntaxRule(explicitRewriter: true)
+struct IfSwitchExpressionRule: Rule {
+    var configuration = SeverityConfiguration<Self>(.warning)
+
+    static let description = RuleDescription(
+        identifier: "if_switch_expression",
+        name: "If and Switch Expression",
+        description: "Enforce the of if and switch statements when they are allowed ",
+        kind: .style,
+        nonTriggeringExamples: IfSwitchExpressionRuleExamples.nonTriggeringExamples,
+        triggeringExamples: IfSwitchExpressionRuleExamples.triggeringExamples
+    )
+}
+private extension IfSwitchExpressionRule {
+    final class Visitor: ViolationsSyntaxVisitor<ConfigurationType> {
+        override func visit(_ node: IfExprSyntax) -> SyntaxVisitorContinueKind {
+            violations.append(node.positionAfterSkippingLeadingTrivia)
+            return .skipChildren
+        }
+        override func visit(_ node: SwitchCaseListSyntax) -> SyntaxVisitorContinueKind {
+            violations.append(node.positionAfterSkippingLeadingTrivia)
+            return .skipChildren
+        }
+    }
+}

Source/SwiftLintBuiltInRules/Rules/Style/IfSwitchExpressionRuleExcamples.swift

@@ -0,0 +1,144 @@
+struct IfSwitchExpressionRuleExamples {
+    static let nonTriggeringExamples: [Example] = [
+        Example("let result = if condition { true } else { false }"),
+        Example("""
+        func f(cond: Bool) -> Int {
+            if cond {
+                // Nothing
+            } else {
+                return 2
+            }
+            return 1
+        }
+        """),
+        Example("""
+        func f(cond: Bool) -> Int {
+            let result = if cond { 1 } else { 2 }
+            return result
+        }
+        """),
+        Example("""
+        let value = 3
+        let description = switch value {
+            case 1 -> "one"
+            case 2 -> "two"
+            default -> "other"
+        }
+        """),
+        Example("""
+        func g(value: Int) -> String {
+            return switch value {
+                case 1 -> "one"
+                case 2 -> "two"
+                default -> "other"
+            }
+        }
+        """),
+        Example("""
+        let result = switch number {
+            case 1 -> "one"
+            case 2 -> "two"
+            case 3 -> "three"
+            default -> "unknown"
+        }
+        """),
+        Example("""
+        func calculate(value: Int) -> Int {
+            return switch value {
+                case 1 -> 10
+                case 2 -> 20
+                case 3 -> 30
+                default -> 0
+            }
+        }
+        """)
+    ]
+
+    static let triggeringExamples: [Example] = [
+        Example("""
+        func f(cond: Bool) {
+            let r: Int
+            if cond {
+                r = 1
+            } else {
+                r = 2
+            }
+        }
+        """),
+        Example("""
+        func f(cond: Bool) -> Int {
+            if cond {
+                return 1
+            } else {
+                return 2
+            }
+        }
+        """),
+        Example("""
+        func f(cond: Bool) -> Int {
+            if cond {
+                // Nothing
+            } else {
+                return 2
+            }
+            return 1
+        }
+        """),
+        Example("""
+        let result: String
+        if condition {
+            result = "yes"
+        } else {
+            result = "no"
+        }
+        """),
+        Example("""
+        func g(value: Int) -> String {
+            let result: String
+            switch value {
+                case 1:
+                    result = "one"
+                case 2:
+                    result = "two"
+                default:
+                    result = "other"
+            }
+            return result
+        }
+        """),
+        Example("""
+        func calculate(value: Int) -> Int {
+            if value == 1 {
+                return 10
+            } else if value == 2 {
+                return 20
+            } else {
+                return 0
+            }
+        }
+        """),
+        Example("""
+        let result: Int
+        if value == 1 {
+            result = 10
+        } else if value == 2 {
+            result = 20
+        } else {
+            result = 0
+        }
+        """),
+        Example("""
+        let description: String
+        switch number {
+            case 1:
+                description = "one"
+            case 2:
+                description = "two"
+            case 3:
+                description = "three"
+            default:
+                description = "unknown"
+        }
+        """)
+    ]
+}