RangeInfo: disallow expressions with non-void type at the start or the end of multi-statement selections. (#8092)

lib/IDE/SwiftSourceDocInfo.cpp

@@ -342,6 +342,37 @@ private:
     std::vector<ASTNode> EndMatches;
     ContextInfo(ASTNode Parent, bool ContainedInRange) : Parent(Parent),
       ContainedInRange(ContainedInRange) {}
+private:
+    bool hasStmtlikeNode(ArrayRef<ASTNode> Nodes) {
+      for (auto N : Nodes) {
+        if (N.is<Stmt*>())
+          return true;
+        // Expression with void type is statement-like.
+        else if (N.is<Expr*>()) {
+          auto *E = N.get<Expr*>();
+          if (auto T = E->getType()) {
+            if (T->isVoid())
+              return true;
+          }
+        } else {
+          // Decls are statement like.
+          return true;
+        }
+      }
+      return false;
+    }
+public:
+    bool hasStmtMatch(RangeMatchKind Kind) {
+      switch(Kind) {
+      case RangeMatchKind::NoneMatch:
+      case RangeMatchKind::RangeMatch:
+        llvm_unreachable("cannot answer these.");
+      case RangeMatchKind::StartMatch:
+        return hasStmtlikeNode(StartMatches);
+      case RangeMatchKind::EndMatch:
+        return hasStmtlikeNode(EndMatches);
+      }
+    }
   };
 
   std::vector<Token> AllTokens;
@@ -654,7 +685,11 @@ public:
       }
     }
 
-    if (!DCInfo.StartMatches.empty() && !DCInfo.EndMatches.empty()) {
+    // Check if the start and end matches have statement-like entities; this
+    // can avoid picking expressions like "a == b" in a list of selected
+    // multi-statement at the start (or the end).
+    if (DCInfo.hasStmtMatch(RangeMatchKind::StartMatch) &&
+        DCInfo.hasStmtMatch(RangeMatchKind::EndMatch)) {
       postAnalysis(DCInfo.EndMatches.back());
       Result = {RangeKind::MultiStatement,
                 /* Last node has the type */
@@ -682,7 +717,7 @@ public:
   ResolvedRangeInfo getResult() {
     if (Result.hasValue())
       return Result.getValue();
-    return ResolvedRangeInfo();
+    return ResolvedRangeInfo(Content);
   }
 
   void analyzeDeclRef(ValueDecl *VD, CharSourceRange Range, Type Ty,
@@ -784,7 +819,7 @@ visitDeclReference(ValueDecl *D, CharSourceRange Range, TypeDecl *CtorTyRef,
 
 ResolvedRangeInfo RangeResolver::resolve() {
   if (!Impl)
-    return ResolvedRangeInfo();
+    return ResolvedRangeInfo(StringRef());
   Impl->enter(ASTNode());
   walk(Impl->File);
   return Impl->getResult();