support SFINAE via template arguments

#feat

Author: alandefreitas

src/lib/AST/ASTVisitor.cpp

@@ -1461,6 +1461,55 @@ populate(
     {
         populate(TI.Requires, RC);
     }
+    else
+    {
+        // If there's no requires clause, check if the template
+        // parameter types we extracted have constraints
+        for (auto it = TI.Params.begin(); it != TI.Params.end(); )
+        {
+            std::unique_ptr<TParam>& param = *it;
+
+            if (auto const* T = dynamic_cast<NonTypeTParam*>(param.get());
+                T &&
+                T->Type &&
+                !T->Type->Constraints.empty())
+            {
+                for (ExprInfo const& constraint: T->Type->Constraints)
+                {
+                    if (!TI.Requires.Written.empty())
+                    {
+                        TI.Requires.Written += " && ";
+                    }
+                    TI.Requires.Written += constraint.Written;
+                }
+                it = TI.Params.erase(it);
+                continue;
+            }
+
+            if (param->Default &&
+                param->Default->isType())
+            {
+                if (auto const* T = dynamic_cast<TypeTArg*>(param->Default.get());
+                    T &&
+                    T->Type &&
+                    !T->Type->Constraints.empty())
+                {
+                    for (ExprInfo const& constraint: T->Type->Constraints)
+                    {
+                        if (!TI.Requires.Written.empty())
+                        {
+                            TI.Requires.Written += " && ";
+                        }
+                        TI.Requires.Written += constraint.Written;
+                    }
+                    it = TI.Params.erase(it);
+                    continue;
+                }
+            }
+
+            ++it;
+        }
+    }
 }
 
 void

test-files/golden-tests/metadata/sfinae.adoc

@@ -22,7 +22,7 @@
 | <<A-09,`A`>> 
 | The partial specialization of A is enabled via a template parameter
 
-| <<A-02,`A&lt;T, void&gt;`>> 
+| <<A-02,`A&lt;T&gt;`>> 
 | Specialization for floating point types
 
 | <<S-02,`S`>> 
@@ -123,7 +123,7 @@ class A;
 
 
 [#A-02]
-== A&lt;T, void&gt;
+== A&lt;T&gt;
 
 
 Specialization for floating point types
@@ -136,7 +136,8 @@ Declared in `&lt;sfinae&period;cpp&gt;`
 [source,cpp,subs="verbatim,replacements,macros,-callouts"]
 ----
 template&lt;class T&gt;
-class <<A-09,A>>&lt;T, void&gt;;
+requires std&colon;&colon;is&lowbar;integral&lowbar;v&lt;T&gt;
+class <<A-09,A>>&lt;T&gt;;
 ----
 
 
@@ -157,7 +158,7 @@ Declared in `&lt;sfinae&period;cpp&gt;`
 ----
 template&lt;
     class T,
-    class = void&gt;
+    class Enable = void&gt;
 struct S;
 ----
 
@@ -261,11 +262,10 @@ Declared in `&lt;sfinae&period;cpp&gt;`
 
 [source,cpp,subs="verbatim,replacements,macros,-callouts"]
 ----
-template&lt;
-    class T,
-    typename = void&gt;
+template&lt;class T&gt;
+requires std&colon;&colon;is&lowbar;integral&lowbar;v&lt;T&gt;
 void
-f10(T* t);
+f10(T value);
 ----
 
 === Description
@@ -346,9 +346,8 @@ Declared in `&lt;sfinae&period;cpp&gt;`
 
 [source,cpp,subs="verbatim,replacements,macros,-callouts"]
 ----
-template&lt;
-    class T,
-    bool = true&gt;
+template&lt;class T&gt;
+requires std&colon;&colon;is&lowbar;integral&lowbar;v&lt;T&gt;
 T
 f5(T value);
 ----
@@ -366,9 +365,8 @@ Declared in `&lt;sfinae&period;cpp&gt;`
 
 [source,cpp,subs="verbatim,replacements,macros,-callouts"]
 ----
-template&lt;
-    class T,
-    bool = true&gt;
+template&lt;class T&gt;
+requires std&colon;&colon;is&lowbar;integral&lowbar;v&lt;T&gt;
 T
 f6(T value);
 ----
@@ -386,9 +384,8 @@ Declared in `&lt;sfinae&period;cpp&gt;`
 
 [source,cpp,subs="verbatim,replacements,macros,-callouts"]
 ----
-template&lt;
-    class T,
-    int = 0&gt;
+template&lt;class T&gt;
+requires std&colon;&colon;is&lowbar;integral&lowbar;v&lt;T&gt;
 void
 f7(T value);
 ----
@@ -408,9 +405,8 @@ Declared in `&lt;sfinae&period;cpp&gt;`
 ----
 template&lt;class T&gt;
 T
-f8(
-    T value,
-    void* = 0);
+f8(T value)
+requires std&colon;&colon;is&lowbar;integral&lowbar;v&lt;T&gt;;
 ----
 
 [#f9]
@@ -428,9 +424,8 @@ Declared in `&lt;sfinae&period;cpp&gt;`
 ----
 template&lt;class T&gt;
 T
-f9(
-    T value,
-    void* = 0);
+f9(T value)
+requires std&colon;&colon;is&lowbar;integral&lowbar;v&lt;T&gt;;
 ----
 
 

test-files/golden-tests/metadata/sfinae.cpp

@@ -36,7 +36,7 @@ T
 f6(T value);
 
 /// Enabled via a non-type template parameter using int instead of bool
-template<class T, std::enable_if_t<T::value1, int> = 0>
+template<class T, std::enable_if_t<std::is_integral_v<T>, int> = 0>
 void f7(T value);
 
 /// Enabled via parameter without helper
@@ -62,7 +62,7 @@ f9(T value, std::enable_if_t<std::is_integral_v<T>>* = 0);
 /// arguments are not accounted for in function template equivalence).
 ///
 template<class T, typename = std::enable_if_t<std::is_integral_v<T>>>
-void f10(T* t);
+void f10(T value);
 
 /// The partial specialization of A is enabled via a template parameter
 template<class T, class Enable = void>
@@ -73,7 +73,7 @@ template<class T>
 class A<T, std::enable_if_t<std::is_integral_v<T>>> {};
 
 /// SFINAE with std::void_t
-template <class T, class = void>
+template <class T, class Enable = void>
 struct S
 {
     void store(const void*) {}

test-files/golden-tests/metadata/sfinae.html

@@ -33,7 +33,7 @@ <h2>Types</h2>
 <td><a href="#A-09"><code>A</code></a> </td><td><span><span>The partial specialization of A is enabled via a template parameter</span></span>
 
 </td></tr><tr>
-<td><a href="#A-02"><code>A&lt;T, void&gt;</code></a> </td><td><span><span>Specialization for floating point types</span></span>
+<td><a href="#A-02"><code>A&lt;T&gt;</code></a> </td><td><span><span>Specialization for floating point types</span></span>
 
 </td></tr><tr>
 <td><a href="#S-02"><code>S</code></a> </td><td><span><span>SFINAE with std::void_t</span></span>
@@ -147,7 +147,7 @@ <h3>Synopsis</h3>
 </div>
 <div>
 <div>
-<h2 id="A-02">A&lt;T, void&gt;</h2>
+<h2 id="A-02">A&lt;T&gt;</h2>
 <div>
 <span><span>Specialization for floating point types</span></span>
 
@@ -161,7 +161,8 @@ <h3>Synopsis</h3>
 <pre>
 <code class="source-code cpp">
 template&lt;class T&gt;
-class <a href="#A-09">A</a>&lt;T, void&gt;;
+requires std::is_integral_v&lt;T&gt;
+class <a href="#A-09">A</a>&lt;T&gt;;
 </code>
 </pre>
 </div>
@@ -185,7 +186,7 @@ <h3>Synopsis</h3>
 <code class="source-code cpp">
 template&lt;
     class T,
-    class = void&gt;
+    class Enable = void&gt;
 struct S;
 </code>
 </pre>
@@ -309,11 +310,10 @@ <h3>Synopsis</h3>
 Declared in <code>&lt;sfinae.cpp&gt;</code></div>
 <pre>
 <code class="source-code cpp">
-template&lt;
-    class T,
-    typename = void&gt;
+template&lt;class T&gt;
+requires std::is_integral_v&lt;T&gt;
 void
-f10(T* t);
+f10(T value);
 </code>
 </pre>
 </div>
@@ -407,9 +407,8 @@ <h3>Synopsis</h3>
 Declared in <code>&lt;sfinae.cpp&gt;</code></div>
 <pre>
 <code class="source-code cpp">
-template&lt;
-    class T,
-    bool = true&gt;
+template&lt;class T&gt;
+requires std::is_integral_v&lt;T&gt;
 T
 f5(T value);
 </code>
@@ -431,9 +430,8 @@ <h3>Synopsis</h3>
 Declared in <code>&lt;sfinae.cpp&gt;</code></div>
 <pre>
 <code class="source-code cpp">
-template&lt;
-    class T,
-    bool = true&gt;
+template&lt;class T&gt;
+requires std::is_integral_v&lt;T&gt;
 T
 f6(T value);
 </code>
@@ -455,9 +453,8 @@ <h3>Synopsis</h3>
 Declared in <code>&lt;sfinae.cpp&gt;</code></div>
 <pre>
 <code class="source-code cpp">
-template&lt;
-    class T,
-    int = 0&gt;
+template&lt;class T&gt;
+requires std::is_integral_v&lt;T&gt;
 void
 f7(T value);
 </code>
@@ -481,9 +478,8 @@ <h3>Synopsis</h3>
 <code class="source-code cpp">
 template&lt;class T&gt;
 T
-f8(
-    T value,
-    void* = 0);
+f8(T value)
+requires std::is_integral_v&lt;T&gt;;
 </code>
 </pre>
 </div>
@@ -505,9 +501,8 @@ <h3>Synopsis</h3>
 <code class="source-code cpp">
 template&lt;class T&gt;
 T
-f9(
-    T value,
-    void* = 0);
+f9(T value)
+requires std::is_integral_v&lt;T&gt;;
 </code>
 </pre>
 </div>