Fix ambiguity in stringification

Happening when using clang and templated operators, clang cannot decide
between the operator provided by ReusableStringStream and the one provided
by the value value as both are templates. This is easily solved by calling
the operator<< through the member syntax.

Fixes #1285

include/internal/catch_tostring.h

@@ -105,7 +105,9 @@ namespace Catch {
         typename std::enable_if<::Catch::Detail::IsStreamInsertable<Fake>::value, std::string>::type
             convert(const Fake& value) {
                 ReusableStringStream rss;
-                rss << value;
+                // NB: call using the function-like syntax to avoid ambiguity with
+                // user-defined templated operator<< under clang.
+                rss.operator<<(value);
                 return rss.str();
         }
 

projects/SelfTest/Baselines/compact.sw.approved.txt

@@ -1065,6 +1065,9 @@ ToStringWhich.tests.cpp:<line number>: passed: ::Catch::Detail::stringify(item)
 ToStringWhich.tests.cpp:<line number>: passed: ::Catch::Detail::stringify( item ) == "operator<<( has_operator )" for: "operator<<( has_operator )"
 ==
 "operator<<( has_operator )"
+ToStringWhich.tests.cpp:<line number>: passed: ::Catch::Detail::stringify( item ) == "operator<<( has_template_operator )" for: "operator<<( has_template_operator )"
+==
+"operator<<( has_template_operator )"
 ToStringWhich.tests.cpp:<line number>: passed: ::Catch::Detail::stringify( v ) == "{ StringMaker<has_maker> }" for: "{ StringMaker<has_maker> }"
 ==
 "{ StringMaker<has_maker> }"

projects/SelfTest/Baselines/console.std.approved.txt

@@ -1084,6 +1084,6 @@ due to unexpected exception with message:
   Why would you throw a std::string?
 
 ===============================================================================
-test cases:  207 | 154 passed |  49 failed |  4 failed as expected
-assertions: 1064 | 936 passed | 107 failed | 21 failed as expected
+test cases:  208 | 155 passed |  49 failed |  4 failed as expected
+assertions: 1065 | 937 passed | 107 failed | 21 failed as expected
 

projects/SelfTest/Baselines/console.sw.approved.txt

@@ -8407,6 +8407,20 @@ with expansion:
   ==
   "operator<<( has_operator )"
 
+-------------------------------------------------------------------------------
+stringify( has_template_operator )
+-------------------------------------------------------------------------------
+ToStringWhich.tests.cpp:<line number>
+...............................................................................
+
+ToStringWhich.tests.cpp:<line number>:
+PASSED:
+  REQUIRE( ::Catch::Detail::stringify( item ) == "operator<<( has_template_operator )" )
+with expansion:
+  "operator<<( has_template_operator )"
+  ==
+  "operator<<( has_template_operator )"
+
 -------------------------------------------------------------------------------
 stringify( vectors<has_maker> )
 -------------------------------------------------------------------------------
@@ -8978,6 +8992,6 @@ Misc.tests.cpp:<line number>:
 PASSED:
 
 ===============================================================================
-test cases:  207 | 141 passed |  62 failed |  4 failed as expected
-assertions: 1078 | 936 passed | 121 failed | 21 failed as expected
+test cases:  208 | 142 passed |  62 failed |  4 failed as expected
+assertions: 1079 | 937 passed | 121 failed | 21 failed as expected
 

projects/SelfTest/Baselines/junit.sw.approved.txt

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <testsuitesloose text artifact
 >
-  <testsuite name="<exe-name>" errors="17" failures="105" tests="1079" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
+  <testsuite name="<exe-name>" errors="17" failures="105" tests="1080" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
     <testcase classname="<exe-name>.global" name="# A test name that starts with a #" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="#1005: Comparing pointer to int and long (NULL can be either on various systems)" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="#1027" time="{duration}"/>
@@ -838,6 +838,7 @@ Tricky.tests.cpp:<line number>
     <testcase classname="<exe-name>.global" name="stringify( has_maker_and_operator )" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="stringify( has_neither )" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="stringify( has_operator )" time="{duration}"/>
+    <testcase classname="<exe-name>.global" name="stringify( has_template_operator )" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="stringify( vectors&lt;has_maker> )" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="stringify( vectors&lt;has_maker_and_operator> )" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="stringify( vectors&lt;has_operator> )" time="{duration}"/>

projects/SelfTest/Baselines/xml.sw.approved.txt

@@ -9366,6 +9366,19 @@ loose text artifact
       </Expression>
       <OverallResult success="true"/>
     </TestCase>
+    <TestCase name="stringify( has_template_operator )" tags="[toString]" filename="projects/<exe-name>/UsageTests/ToStringWhich.tests.cpp" >
+      <Expression success="true" type="REQUIRE" filename="projects/<exe-name>/UsageTests/ToStringWhich.tests.cpp" >
+        <Original>
+          ::Catch::Detail::stringify( item ) == "operator&lt;&lt;( has_template_operator )"
+        </Original>
+        <Expanded>
+          "operator&lt;&lt;( has_template_operator )"
+==
+"operator&lt;&lt;( has_template_operator )"
+        </Expanded>
+      </Expression>
+      <OverallResult success="true"/>
+    </TestCase>
     <TestCase name="stringify( vectors&lt;has_maker> )" tags="[toString]" filename="projects/<exe-name>/UsageTests/ToStringWhich.tests.cpp" >
       <Expression success="true" type="REQUIRE" filename="projects/<exe-name>/UsageTests/ToStringWhich.tests.cpp" >
         <Original>
@@ -9923,7 +9936,7 @@ loose text artifact
       </Section>
       <OverallResult success="true"/>
     </TestCase>
-    <OverallResults successes="936" failures="122" expectedFailures="21"/>
+    <OverallResults successes="937" failures="122" expectedFailures="21"/>
   </Group>
-  <OverallResults successes="936" failures="121" expectedFailures="21"/>
+  <OverallResults successes="937" failures="121" expectedFailures="21"/>
 </Catch>

projects/SelfTest/UsageTests/ToStringWhich.tests.cpp

@@ -20,6 +20,7 @@ struct has_operator { };
 struct has_maker {};
 struct has_maker_and_operator {};
 struct has_neither {};
+struct has_template_operator {};
 
 std::ostream& operator<<(std::ostream& os, const has_operator&) {
     os << "operator<<( has_operator )";
@@ -31,6 +32,12 @@ std::ostream& operator<<(std::ostream& os, const has_maker_and_operator&) {
     return os;
 }
 
+template <typename StreamT>
+StreamT& operator<<(StreamT& os, const has_template_operator&) {
+    os << "operator<<( has_template_operator )";
+    return os;
+}
+
 namespace Catch {
     template<>
     struct StringMaker<has_maker> {
@@ -69,6 +76,12 @@ TEST_CASE("stringify( has_neither )", "[toString]") {
     REQUIRE( ::Catch::Detail::stringify(item) == "{ !!! }" );
 }
 
+// Call the templated operator
+TEST_CASE( "stringify( has_template_operator )", "[toString]" ) {
+    has_template_operator item;
+    REQUIRE( ::Catch::Detail::stringify( item ) == "operator<<( has_template_operator )" );
+}
+
 
 // Vectors...