From 5cc1eaf8a159d8b52e36fc1ba0df040ad905886c Mon Sep 17 00:00:00 2001
From: mattias <mattias@idefix.freepascal.org>
Date: Sat, 10 Aug 2019 06:48:04 +0000
Subject: [PATCH] fcl-passrc: no function result not set warning for fieldless
 record

---
 .../fcl-passrc/src/pasuseanalyzer.pas         | 69 ++++++++++++++-----
 .../fcl-passrc/tests/tcuseanalyzer.pas        | 20 ++++++
 2 files changed, 71 insertions(+), 18 deletions(-)

diff --git a/compiler/packages/fcl-passrc/src/pasuseanalyzer.pas b/compiler/packages/fcl-passrc/src/pasuseanalyzer.pas
index 038fe23..38b7766 100644
--- a/compiler/packages/fcl-passrc/src/pasuseanalyzer.pas
+++ b/compiler/packages/fcl-passrc/src/pasuseanalyzer.pas
@@ -281,6 +281,7 @@ type
     procedure EmitTypeHints(El: TPasType); virtual;
     procedure EmitVariableHints(El: TPasVariable); virtual;
     procedure EmitProcedureHints(El: TPasProcedure); virtual;
+    procedure EmitFunctionResultHints(El: TPasFunction); virtual;
   public
     constructor Create;
     destructor Destroy; override;
@@ -2568,9 +2569,7 @@ var
   Arg: TPasArgument;
   Usage: TPAElement;
   ProcScope: TPasProcedureScope;
-  PosEl: TPasElement;
   DeclProc, ImplProc: TPasProcedure;
-  FuncType: TPasFunctionType;
 begin
   {$IFDEF VerbosePasAnalyzer}
   writeln('TPasAnalyzer.EmitProcedureHints ',GetElModName(El));
@@ -2637,22 +2636,7 @@ begin
       end;
     // check result
     if (El.ProcType is TPasFunctionType) then
-      begin
-      FuncType:=TPasFunctionType(TPasProcedure(El).ProcType);
-      PosEl:=FuncType.ResultEl;
-      if (ProcScope.ImplProc<>nil)
-          and (TPasFunction(ProcScope.ImplProc).FuncType.ResultEl<>nil) then
-        PosEl:=TPasFunction(ProcScope.ImplProc).FuncType.ResultEl;
-      Usage:=FindElement(FuncType.ResultEl);
-      if (Usage=nil) or (Usage.Access in [paiaNone,paiaRead]) then
-        // result was never used
-        EmitMessage(20170313214038,mtHint,nPAFunctionResultDoesNotSeemToBeSet,
-          sPAFunctionResultDoesNotSeemToBeSet,[],PosEl)
-      else
-        begin
-        // result was used
-        end;
-      end;
+      EmitFunctionResultHints(TPasFunction(El));
     end;
 
   if El.Body<>nil then
@@ -2663,6 +2647,55 @@ begin
     end;
 end;
 
+procedure TPasAnalyzer.EmitFunctionResultHints(El: TPasFunction);
+var
+  FuncType: TPasFunctionType;
+  Usage: TPAElement;
+  TypeEl: TPasType;
+  Members: TFPList;
+  i: Integer;
+  Member: TPasElement;
+  HasFields: Boolean;
+  PosEl: TPasResultElement;
+  ProcScope: TPasProcedureScope;
+begin
+  FuncType:=El.FuncType;
+  Usage:=FindElement(FuncType.ResultEl);
+  if (Usage=nil) or (Usage.Access in [paiaNone,paiaRead]) then
+    begin
+    // result was never set
+    TypeEl:=Resolver.ResolveAliasType(FuncType.ResultEl.ResultType);
+    if TypeEl is TPasRecordType then
+      begin
+      Members:=TPasRecordType(TypeEl).Members;
+      HasFields:=false;
+      for i:=0 to Members.Count-1 do
+        begin
+        Member:=TPasElement(Members[i]);
+        if Member.ClassType=TPasVariable then
+          begin
+          HasFields:=true;
+          break;
+          end;
+        end;
+      if not HasFields then
+        // empty record -> no hint
+        exit;
+      end;
+    PosEl:=FuncType.ResultEl;
+    ProcScope:=El.CustomData as TPasProcedureScope;
+    if (ProcScope.ImplProc<>nil)
+        and (TPasFunction(ProcScope.ImplProc).FuncType.ResultEl<>nil) then
+      PosEl:=TPasFunction(ProcScope.ImplProc).FuncType.ResultEl;
+    EmitMessage(20170313214038,mtHint,nPAFunctionResultDoesNotSeemToBeSet,
+      sPAFunctionResultDoesNotSeemToBeSet,[],PosEl)
+    end
+  else
+    begin
+    // result was used
+    end;
+end;
+
 constructor TPasAnalyzer.Create;
 var
   m: TPAUseMode;
diff --git a/compiler/packages/fcl-passrc/tests/tcuseanalyzer.pas b/compiler/packages/fcl-passrc/tests/tcuseanalyzer.pas
index d06ebfb..d0fe267 100644
--- a/compiler/packages/fcl-passrc/tests/tcuseanalyzer.pas
+++ b/compiler/packages/fcl-passrc/tests/tcuseanalyzer.pas
@@ -128,6 +128,7 @@ type
     procedure TestM_Hint_FunctionResultDoesNotSeemToBeSet;
     procedure TestM_Hint_FunctionResultDoesNotSeemToBeSet_Abstract;
     procedure TestM_Hint_FunctionResultRecord;
+    procedure TestM_Hint_FunctionResultRecordEmpty;
     procedure TestM_Hint_FunctionResultPassRecordElement;
     procedure TestM_Hint_FunctionResultAssembler;
     procedure TestM_Hint_FunctionResultExit;
@@ -2165,6 +2166,25 @@ begin
   CheckUseAnalyzerUnexpectedHints;
 end;
 
+procedure TTestUseAnalyzer.TestM_Hint_FunctionResultRecordEmpty;
+begin
+  StartProgram(true);
+  Add([
+  '{$modeswitch AdvancedRecords}',
+  'type',
+  '  TEmpty = record',
+  '    class function Create: TEmpty; static;',
+  '  end;',
+  'class function TEmpty.Create: TEmpty;',
+  'begin',
+  'end;',
+  'begin',
+  '  TEmpty.Create;',
+  '']);
+  AnalyzeProgram;
+  CheckUseAnalyzerUnexpectedHints;
+end;
+
 procedure TTestUseAnalyzer.TestM_Hint_FunctionResultPassRecordElement;
 begin
   StartProgram(true);