Make StringRef's operator std::string explicit

This way it is explicit when there is a `StringRef` -> `std::string`
conversion and makes it easier to look for allocations that could
be avoided.

Doing this has already removed one allocation per registered test
case, as there was a completely pointless `StringRef` -> `std::string`
conversion when parsing tags of a test case.

include/internal/catch_assertionresult.cpp

@@ -56,13 +56,13 @@ namespace Catch {
         if( isFalseTest( m_info.resultDisposition ) )
             return "!(" + m_info.capturedExpression + ")";
         else
-            return m_info.capturedExpression;
+            return static_cast<std::string>(m_info.capturedExpression);
     }
 
     std::string AssertionResult::getExpressionInMacro() const {
         std::string expr;
         if( m_info.macroName[0] == 0 )
-            expr = m_info.capturedExpression;
+            expr = static_cast<std::string>(m_info.capturedExpression);
         else {
             expr.reserve( m_info.macroName.size() + m_info.capturedExpression.size() + 4 );
             expr += m_info.macroName;

include/internal/catch_message.cpp

@@ -113,7 +113,7 @@ namespace Catch {
             case ',':
                 if (start != pos && openings.size() == 0) {
                     m_messages.emplace_back(macroName, lineInfo, resultType);
-                    m_messages.back().message = trimmed(start, pos);
+                    m_messages.back().message = static_cast<std::string>(trimmed(start, pos));
                     m_messages.back().message += " := ";
                     start = pos;
                 }
@@ -121,7 +121,7 @@ namespace Catch {
         }
         assert(openings.size() == 0 && "Mismatched openings");
         m_messages.emplace_back(macroName, lineInfo, resultType);
-        m_messages.back().message = trimmed(start, names.size() - 1);
+        m_messages.back().message = static_cast<std::string>(trimmed(start, names.size() - 1));
         m_messages.back().message += " := ";
     }
     Capturer::~Capturer() {

include/internal/catch_run_context.cpp

@@ -279,7 +279,7 @@ namespace Catch {
         // Don't rebuild the result -- the stringification itself can cause more fatal errors
         // Instead, fake a result data.
         AssertionResultData tempResult( ResultWas::FatalErrorCondition, { false } );
-        tempResult.message = message;
+        tempResult.message = static_cast<std::string>(message);
         AssertionResult result(m_lastAssertionInfo, tempResult);
 
         assertionEnded(result);
@@ -442,7 +442,7 @@ namespace Catch {
         m_lastAssertionInfo = info;
 
         AssertionResultData data( resultType, LazyExpression( false ) );
-        data.message = message;
+        data.message = static_cast<std::string>(message);
         AssertionResult assertionResult{ m_lastAssertionInfo, data };
         assertionEnded( assertionResult );
         if( !assertionResult.isOk() )

include/internal/catch_stringref.h

@@ -23,6 +23,7 @@ namespace Catch {
     class StringRef {
     public:
         using size_type = std::size_t;
+        using const_iterator = const char*;
 
     private:
         friend struct StringRefTestAccess;
@@ -78,7 +79,7 @@ namespace Catch {
             return *this;
         }
 
-        operator std::string() const;
+        explicit operator std::string() const;
 
         void swap( StringRef& other ) noexcept;
 
@@ -105,6 +106,10 @@ namespace Catch {
         // Note that the pointer can change when if the StringRef is a substring
         auto currentData() const noexcept -> char const*;
 
+    public: // iterators
+        const_iterator begin() const { return m_start; }
+        const_iterator end() const { return m_start + m_size; }
+
     private: // ownership queries - may not be consistent between calls
         auto isOwned() const noexcept -> bool;
         auto isSubstring() const noexcept -> bool;

include/internal/catch_test_case_info.cpp

@@ -59,8 +59,7 @@ namespace Catch {
         std::vector<std::string> tags;
         std::string desc, tag;
         bool inTag = false;
-        std::string _descOrTags = nameAndTags.tags;
+        for (char c : nameAndTags.tags) {
-        for (char c : _descOrTags) {
             if( !inTag ) {
                 if( c == '[' )
                     inTag = true;
@@ -93,7 +92,7 @@ namespace Catch {
             tags.push_back( "." );
         }
 
-        TestCaseInfo info( nameAndTags.name, _className, desc, tags, _lineInfo );
+        TestCaseInfo info( static_cast<std::string>(nameAndTags.name), _className, desc, tags, _lineInfo );
         return TestCase( _testCase, std::move(info) );
     }
 

include/internal/catch_test_case_registry_impl.cpp

@@ -105,7 +105,7 @@ namespace Catch {
     }
 
     std::string extractClassName( StringRef const& classOrQualifiedMethodName ) {
-        std::string className = classOrQualifiedMethodName;
+        std::string className(classOrQualifiedMethodName);
         if( startsWith( className, '&' ) )
         {
             std::size_t lastColons = className.rfind( "::" );

include/internal/catch_tostring.h

@@ -654,7 +654,7 @@ namespace Catch { \
     template<> struct StringMaker<enumName> { \
         static std::string convert( enumName value ) { \
             static const auto& enumInfo = ::Catch::getMutableRegistryHub().getMutableEnumValuesRegistry().registerEnum( #enumName, #__VA_ARGS__, { __VA_ARGS__ } ); \
-            return enumInfo.lookup( static_cast<int>( value ) ); \
+            return static_cast<std::string>(enumInfo.lookup( static_cast<int>( value ) )); \
         } \
     }; \
 }

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

@@ -1043,8 +1043,6 @@ String.tests.cpp:<line number>: passed: stdStr == "a stringref" for: "a stringre
 String.tests.cpp:<line number>: passed: stdStr.size() == sr.size() for: 11 == 11
 String.tests.cpp:<line number>: passed: stdStr == "a stringref" for: "a stringref" == "a stringref"
 String.tests.cpp:<line number>: passed: stdStr.size() == sr.size() for: 11 == 11
-String.tests.cpp:<line number>: passed: stdStr == "a stringref" for: "a stringref" == "a stringref"
-String.tests.cpp:<line number>: passed: stdStr.size() == sr.size() for: 11 == 11
 ToStringChrono.tests.cpp:<line number>: passed: minute == seconds for: 1 m == 60 s
 ToStringChrono.tests.cpp:<line number>: passed: hour != seconds for: 1 h != 60 s
 ToStringChrono.tests.cpp:<line number>: passed: micro != milli for: 1 us != 1 ms

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

@@ -1381,5 +1381,5 @@ due to unexpected exception with message:
 
 ===============================================================================
 test cases:  300 |  226 passed |  70 failed |  4 failed as expected
-assertions: 1559 | 1407 passed | 131 failed | 21 failed as expected
+assertions: 1557 | 1405 passed | 131 failed | 21 failed as expected
 

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

@@ -7783,24 +7783,6 @@ String.tests.cpp:<line number>: PASSED:
 with expansion:
   17 == 17
 
--------------------------------------------------------------------------------
-StringRef
-  to std::string
-  implicitly constructed
--------------------------------------------------------------------------------
-String.tests.cpp:<line number>
-...............................................................................
-
-String.tests.cpp:<line number>: PASSED:
-  REQUIRE( stdStr == "a stringref" )
-with expansion:
-  "a stringref" == "a stringref"
-
-String.tests.cpp:<line number>: PASSED:
-  REQUIRE( stdStr.size() == sr.size() )
-with expansion:
-  11 == 11
-
 -------------------------------------------------------------------------------
 StringRef
   to std::string
@@ -12462,5 +12444,5 @@ Misc.tests.cpp:<line number>: PASSED:
 
 ===============================================================================
 test cases:  300 |  210 passed |  86 failed |  4 failed as expected
-assertions: 1576 | 1407 passed | 148 failed | 21 failed as expected
+assertions: 1574 | 1405 passed | 148 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="132" tests="1577" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
+  <testsuite name="<exe-name>" errors="17" failures="132" tests="1575" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
     <properties>
       <property name="filters" value="~[!nonportable]~[!benchmark]~[approvals]"/>
       <property name="random-seed" value="1"/>
@@ -726,7 +726,6 @@ Matchers.tests.cpp:<line number>
     <testcase classname="<exe-name>.global" name="StringRef/from std::string/implicitly constructed" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="StringRef/from std::string/explicitly constructed" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="StringRef/from std::string/assigned" time="{duration}"/>
-    <testcase classname="<exe-name>.global" name="StringRef/to std::string/implicitly constructed" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="StringRef/to std::string/explicitly constructed" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="StringRef/to std::string/assigned" time="{duration}"/>
     <testcase classname="<exe-name>.global" name="Stringifying std::chrono::duration helpers" time="{duration}"/>

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

@@ -9601,28 +9601,6 @@ Message from section two
         </Section>
         <OverallResults successes="2" failures="0" expectedFailures="0"/>
       </Section>
-      <Section name="to std::string" filename="projects/<exe-name>/IntrospectiveTests/String.tests.cpp" >
-        <Section name="implicitly constructed" filename="projects/<exe-name>/IntrospectiveTests/String.tests.cpp" >
-          <Expression success="true" type="REQUIRE" filename="projects/<exe-name>/IntrospectiveTests/String.tests.cpp" >
-            <Original>
-              stdStr == "a stringref"
-            </Original>
-            <Expanded>
-              "a stringref" == "a stringref"
-            </Expanded>
-          </Expression>
-          <Expression success="true" type="REQUIRE" filename="projects/<exe-name>/IntrospectiveTests/String.tests.cpp" >
-            <Original>
-              stdStr.size() == sr.size()
-            </Original>
-            <Expanded>
-              11 == 11
-            </Expanded>
-          </Expression>
-          <OverallResults successes="2" failures="0" expectedFailures="0"/>
-        </Section>
-        <OverallResults successes="2" failures="0" expectedFailures="0"/>
-      </Section>
       <Section name="to std::string" filename="projects/<exe-name>/IntrospectiveTests/String.tests.cpp" >
         <Section name="explicitly constructed" filename="projects/<exe-name>/IntrospectiveTests/String.tests.cpp" >
           <Expression success="true" type="REQUIRE" filename="projects/<exe-name>/IntrospectiveTests/String.tests.cpp" >
@@ -14834,7 +14812,7 @@ loose text artifact
       </Section>
       <OverallResult success="true"/>
     </TestCase>
-    <OverallResults successes="1407" failures="149" expectedFailures="21"/>
+    <OverallResults successes="1405" failures="149" expectedFailures="21"/>
   </Group>
-  <OverallResults successes="1407" failures="148" expectedFailures="21"/>
+  <OverallResults successes="1405" failures="148" expectedFailures="21"/>
 </Catch>

projects/SelfTest/IntrospectiveTests/String.tests.cpp

@@ -142,11 +142,6 @@ TEST_CASE( "StringRef", "[Strings][StringRef]" ) {
     SECTION( "to std::string" ) {
         StringRef sr = "a stringref";
 
-        SECTION( "implicitly constructed" ) {
-            std::string stdStr = sr;
-            REQUIRE( stdStr == "a stringref" );
-            REQUIRE( stdStr.size() == sr.size() );
-        }
         SECTION( "explicitly constructed" ) {
             std::string stdStr( sr );
             REQUIRE( stdStr == "a stringref" );
@@ -154,7 +149,7 @@ TEST_CASE( "StringRef", "[Strings][StringRef]" ) {
         }
         SECTION( "assigned" ) {
             std::string stdStr;
-            stdStr = sr;
+            stdStr = static_cast<std::string>(sr);
             REQUIRE( stdStr == "a stringref" );
             REQUIRE( stdStr.size() == sr.size() );
         }