[Coverage] Also walk MacroExpansionDecls

Make sure we walk macro expansion decls to handle
cases where e.g a binding introduces control flow.
This should be a pretty uncommon case since bindings
introduced by macros aren't actually usable when
expanded in local contexts, but handle it all the
same.

Author: hamishknight

lib/SIL/IR/SILProfiler.cpp

@@ -258,9 +258,12 @@ bool shouldSkipExpr(Expr *E) {
 /// Whether the children of a decl that isn't explicitly handled should be
 /// walked.
 static bool shouldWalkIntoUnhandledDecl(const Decl *D) {
-  // We want to walk into the initializer for a pattern binding decl. This
-  // allows us to map LazyInitializerExprs.
-  return isa<PatternBindingDecl>(D);
+  // We want to walk into initializers for bindings, and the expansions of
+  // MacroExpansionDecls, which will be nested within MacroExpansionExprs in
+  // local contexts. We won't record any regions within the macro expansion,
+  // but still need to walk to get accurate counter information in case e.g
+  // there's a throwing function call in the expansion.
+  return isa<PatternBindingDecl>(D) || isa<MacroExpansionDecl>(D);
 }
 
 /// Whether the expression \c E could potentially throw an error.

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -2218,6 +2218,15 @@ public struct SingleMemberStubMacro: DeclarationMacro {
   }
 }
 
+public struct DeclMacroWithControlFlow: DeclarationMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) throws -> [DeclSyntax] {
+    return ["let _ = .random() ? try throwingFn() : 0"]
+  }
+}
+
 public struct GenerateStubsForProtocolRequirementsMacro: PeerMacro, ExtensionMacro {
   public static func expansion(
     of node: AttributeSyntax,

test/Profiler/coverage_macros.swift

@@ -31,6 +31,9 @@ macro id<T>(_: T) -> T = #externalMacro(module: "MacroDefinition", type: "TupleM
 @attached(body)
 macro BodyMacroWithControlFlow() = #externalMacro(module: "MacroDefinition", type: "BodyMacroWithControlFlow")
 
+@freestanding(declaration, names: arbitrary)
+macro declMacroWithControlFlow() = #externalMacro(module: "MacroDefinition", type: "DeclMacroWithControlFlow")
+
 // This needs to be matched up here due to the sorting of the SIL; just make
 // sure we emit the counter increments for the error branches.
 // CHECK-LABEL: sil hidden @$s15coverage_macros5test2Si_SityKF
@@ -129,3 +132,10 @@ func test7() throws {
   guard .random() else { return }
   print("hello")
 }
+
+// CHECK-LABEL: sil_coverage_map{{.*}}s15coverage_macros5test8yyKF
+func test8() throws {             // CHECK-NEXT: [[@LINE]]:21   -> [[@LINE+4]]:2 : 0
+  guard .random() else { return } // CHECK-NEXT: [[@LINE]]:24   -> [[@LINE]]:34  : 1
+                                  // CHECK-NEXT: [[@LINE-1]]:34 -> [[@LINE+2]]:2 : (0 - 1)
+  #declMacroWithControlFlow       // CHECK-NEXT: [[@LINE]]:28   -> [[@LINE+1]]:2 : ((0 - 1) - 3)
+}