[CodeCompletion] Skip conjuction elements that are unrelated to the code completion token

Author: ahoppen

lib/Sema/CSSyntacticElement.cpp

@@ -1030,6 +1030,23 @@ class SyntacticElementConstraintGenerator
 
     SmallVector<ElementInfo, 4> elements;
     for (auto element : braceStmt->getElements()) {
+      if (cs.isForCodeCompletion() &&
+          !cs.containsIDEInspectionTarget(element)) {
+        // Statements and expressions can't influence the expresion that
+        // contains the code completion token. To improve performance, skip
+        // type checking them entirely.
+        if (element.is<Expr *>() && !element.isExpr(ExprKind::TypeJoin)) {
+          // Type join expressions are not really pure expressions, they kind of
+          // declare new type variables and are important to a result builder's
+          // structure. Don't skip them.
+          continue;
+        } else if (element.is<Stmt *>() && !element.isStmt(StmtKind::Guard)) {
+          // Guard statements might define variables that are used in the code
+          // completion expression. Don't skip them.
+          continue;
+        }
+      }
+
       if (auto *decl = element.dyn_cast<Decl *>()) {
         if (auto *PDB = dyn_cast<PatternBindingDecl>(decl)) {
           visitPatternBinding(PDB, elements);

test/IDE/complete_in_result_builder.swift

@@ -274,3 +274,31 @@ func testAmbiguousInResultBuilder() {
 // AMBIGUOUS_IN_RESULT_BUILDER: End completions
   }
 }
+
+func testCompleteGlobalInResultBuilderIf() {
+  func buildView(@ViewBuilder2 content: () -> MyView) {}
+
+  @resultBuilder public struct ViewBuilder2 {
+    static func buildBlock() -> MyView { fatalError() }
+    static func buildBlock(_ content: MyView) -> MyView { fatalError() }
+    static func buildIf(_ content: MyView?) -> MyView? { fatalError() }
+    static func buildEither(first: MyView) -> MyView { fatalError() }
+    static func buildEither(second: MyView) -> MyView { fatalError() }
+  }
+
+  struct MyView {}
+
+  func test() {
+    buildView {
+      if true {
+        MyView()
+      } else {
+        #^GLOBAL_IN_RESULT_BUILDER_IF^#
+      }
+    }
+  }
+
+  // GLOBAL_IN_RESULT_BUILDER_IF: Begin completions
+  // GLOBAL_IN_RESULT_BUILDER_IF-DAG: Decl[Struct]/Local/TypeRelation[Convertible]: MyView[#MyView#]; name=MyView
+  // GLOBAL_IN_RESULT_BUILDER_IF: End completions
+}