[Macros] Add test cases for operator foldings

test/Macros/macro_plugin_opfolding.swift

@@ -0,0 +1,106 @@
+// REQUIRES: swift_swift_parser
+
+// RUN: %empty-directory(%t)
+// RUN: %empty-directory(%t/plugins)
+// RUN: split-file %s %t
+
+//== Build the plugin library
+// RUN: %host-build-swift \
+// RUN:   -swift-version 5 \
+// RUN:   -emit-library \
+// RUN:   -o %t/plugins/%target-library-name(MacroDefinition) \
+// RUN:   -module-name=MacroDefinition \
+// RUN:   %t/MacroDefinition.swift \
+// RUN:   -g -no-toolchain-stdlib-rpath
+
+// RUN: env SWIFT_DUMP_PLUGIN_MESSAGING=1 %target-swift-frontend \
+// RUN:   -typecheck -verify \
+// RUN:   -swift-version 5 \
+// RUN:   -external-plugin-path %t/plugins#%swift-plugin-server \
+// RUN:   -Rmacro-loading -verify-ignore-unknown \
+// RUN:   -module-name MyApp \
+// RUN:   %t/test.swift
+
+//--- MacroDefinition.swift
+
+import SwiftOperators
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import SwiftSyntaxMacros
+
+final class SequenceFinder: SyntaxVisitor {
+  var foundSequenceExpr: Bool = false
+  init() {
+    super.init(viewMode: .sourceAccurate)
+  }
+
+  override func visit(_ node: SequenceExprSyntax) -> SyntaxVisitorContinueKind {
+    foundSequenceExpr = true
+    return .visitChildren
+  }
+}
+
+func hasSequenceExpr(_ node: some SyntaxProtocol) -> Bool {
+  let finder = SequenceFinder()
+  finder.walk(node)
+  return finder.foundSequenceExpr
+}
+
+public struct OpFoldingTestMacro {}
+
+extension OpFoldingTestMacro: PeerMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    providingPeersOf declaration: some DeclSyntaxProtocol,
+    in context: some MacroExpansionContext
+  ) throws -> [DeclSyntax] {
+    precondition(!hasSequenceExpr(node))
+    precondition(hasSequenceExpr(declaration))
+    return []
+  }
+}
+
+extension OpFoldingTestMacro: MemberAttributeMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    attachedTo declaration: some DeclGroupSyntax,
+    providingAttributesFor member: some DeclSyntaxProtocol,
+    in context: some MacroExpansionContext
+  ) throws -> [AttributeSyntax] {
+    precondition(!hasSequenceExpr(node))
+    precondition(hasSequenceExpr(declaration))
+    precondition(hasSequenceExpr(member))
+    return []
+  }
+}
+
+extension OpFoldingTestMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) throws -> ExprSyntax {
+    precondition(!hasSequenceExpr(node))
+    return "1"
+  }
+}
+
+//--- test.swift
+
+@attached(peer)
+macro OpFoldingTest(_: Any) = #externalMacro(module: "MacroDefinition", type: "OpFoldingTestMacro")
+
+@freestanding(expression)
+macro OpFoldingTestExpr(_: Any) -> Int = #externalMacro(module: "MacroDefinition", type: "OpFoldingTestMacro")
+
+var a = 1, b = 2
+
+@OpFoldingTest(1 + a)
+func peerTest() {}
+
+@OpFoldingTest(1 + b)
+struct S {
+  var value =  a + b
+  func member(foo: Int, bar: Int) { _ = foo + bar }
+}
+
+let valu = #OpFoldingTestExpr(a + b)