From 5654630099cf0eac6b12270787938f5d69f15e21 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Sat, 16 Nov 2019 19:49:43 +0100
Subject: [PATCH] Fixed #8978 (False positive: Variable assigned value that is
 never used when assigning via iterator)

---
 lib/checkunusedvar.cpp | 25 +++++++++++++++++--------
 test/testunusedvar.cpp |  9 +++++++++
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index ef5cac7b6..eff8a38be 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1185,16 +1185,25 @@ void CheckUnusedVar::checkFunctionVariableUsage()
                 op1tok = op1tok->astOperand1();
 
             const Variable *op1Var = op1tok ? op1tok->variable() : nullptr;
-            if (op1Var && op1Var->isReference() && op1Var->nameToken() != tok->astOperand1())
-                // todo: check references
-                continue;
+            if (op1Var) {
+                if (op1Var->isReference() && op1Var->nameToken() != tok->astOperand1())
+                    // todo: check references
+                    continue;
 
-            if (op1Var && op1Var->isStatic())
-                // todo: check static variables
-                continue;
+                if (op1Var->isStatic())
+                    // todo: check static variables
+                    continue;
 
-            if (op1Var && op1Var->nameToken()->isAttributeUnused())
-                continue;
+                if (op1Var->nameToken()->isAttributeUnused())
+                    continue;
+
+                // Bailout for unknown template classes, we have no idea what side effects such assignments have
+                if (mTokenizer->isCPP() &&
+                    op1Var->isClass() &&
+                    (!op1Var->valueType() || op1Var->valueType()->type == ValueType::Type::UNKNOWN_TYPE) &&
+                    Token::findsimplematch(op1Var->typeStartToken(), "<", op1Var->typeEndToken()))
+                    continue;
+            }
 
             // Is there a redundant assignment?
             const Token *start = tok->findExpressionStartEndTokens().second->next();
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 1a0d0cf0f..2dc908f86 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -201,6 +201,7 @@ private:
         TEST_CASE(bracesInitCpp11);// #7895 - "int var{123}" initialization
 
         TEST_CASE(argument);
+        TEST_CASE(argumentClass);
         TEST_CASE(escapeAlias); // #9150
     }
 
@@ -4578,6 +4579,14 @@ private:
         ASSERT_EQUALS("[test.cpp:2]: (style) Variable 'foo.x' is assigned a value that is never used.\n", errout.str());
     }
 
+    void argumentClass() {
+        functionVariableUsage(
+            "void foo(std::insert_iterator<C> it) {\n"
+            "  it = 123;\n"
+            "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void escapeAlias() {
         functionVariableUsage(
             "struct A {\n"