Add location information and improve clarity of diagnostics.

This patch is a first step towards diagnostics refactoring in the context of
non-differentiable propagators.

include/clad/Differentiator/VisitorBase.h

@@ -394,14 +394,12 @@ namespace clad {
     /// to avoid recomputation.
     static bool UsefulToStore(clang::Expr* E);
     /// A flag for silencing warnings/errors output by diag function.
-    bool silenceDiags = false;
     /// Shorthand to issues a warning or error.
     template <std::size_t N>
     void diag(clang::DiagnosticsEngine::Level level, // Warning or Error
               clang::SourceLocation loc, const char (&format)[N],
               llvm::ArrayRef<llvm::StringRef> args = {}) {
-      if (!silenceDiags)
-        m_Builder.diag(level, loc, format, args);
+      m_Builder.diag(level, loc, format, args);
     }
 
     /// Creates unique identifier of the form "_nameBase<number>" that is
@@ -584,17 +582,14 @@ namespace clad {
     clang::Expr* GetSingleArgCentralDiffCall(
         clang::Expr* targetFuncCall, clang::Expr* targetArg, unsigned targetPos,
         unsigned numArgs, llvm::SmallVectorImpl<clang::Expr*>& args);
+
     /// Emits diagnostic messages on differentiation (or lack thereof) for
     /// call expressions.
     ///
-    /// \param[in] \c funcName The name of the underlying function of the
-    /// call expression.
+    /// \param[in] \c FD - The function declaration.
     /// \param[in] \c srcLoc Any associated source location information.
-    /// \param[in] \c isDerived A flag to determine if differentiation of the
-    /// call expression was successful.
-    void CallExprDiffDiagnostics(llvm::StringRef funcName,
-                                 clang::SourceLocation srcLoc,
-                                 bool isDerived);
+    void CallExprDiffDiagnostics(const clang::FunctionDecl* FD,
+                                 clang::SourceLocation srcLoc);
 
     clang::QualType DetermineCladArrayValueType(clang::QualType T);
 

lib/Differentiator/BaseForwardModeVisitor.cpp

@@ -63,7 +63,6 @@ DerivativeAndOverload
 BaseForwardModeVisitor::Derive(const FunctionDecl* FD,
                                const DiffRequest& request) {
   assert(m_DiffReq == request && "Can't pass two different requests!");
-  silenceDiags = !request.VerboseDiags;
   m_Functor = request.Functor;
   assert(m_DiffReq.Mode == DiffMode::forward);
   assert(!m_DerivativeInFlight &&
@@ -1331,7 +1330,7 @@ StmtDiff BaseForwardModeVisitor::VisitCallExpr(const CallExpr* CE) {
           GetSingleArgCentralDiffCall(fnCallee, CallArgs[0],
                                       /*targetPos=*/0, /*numArgs=*/1, CallArgs);
     }
-    CallExprDiffDiagnostics(FD->getNameAsString(), CE->getBeginLoc(), callDiff);
+    CallExprDiffDiagnostics(FD, CE->getBeginLoc());
     if (!callDiff) {
       auto zero =
           ConstantFolder::synthesizeLiteral(m_Context.IntTy, m_Context, 0);

lib/Differentiator/DerivativeBuilder.cpp

@@ -194,15 +194,8 @@ static void registerDerivative(FunctionDecl* derivedFD, Sema& semaRef) {
     }
     if (!NSD) {
       NSD = utils::LookupNSD(m_Sema, namespaceID, namespaceShouldExist);
-      if (!forCustomDerv && !NSD) {
-        diag(DiagnosticsEngine::Warning, noLoc,
-             "Numerical differentiation is diabled using the "
-             "-DCLAD_NO_NUM_DIFF "
-             "flag, this means that every try to numerically differentiate a "
-             "function will fail! Remove the flag to revert to default "
-             "behaviour.");
+      if (!NSD)
         return R;
-      }
     }
     DeclContext* DC = NSD;
 

lib/Differentiator/ReverseModeForwPassVisitor.cpp

@@ -20,7 +20,6 @@ DerivativeAndOverload
 ReverseModeForwPassVisitor::Derive(const FunctionDecl* FD,
                                    const DiffRequest& request) {
   assert(m_DiffReq == request);
-  silenceDiags = !request.VerboseDiags;
 
   assert(m_DiffReq.Mode == DiffMode::reverse_mode_forward_pass);
 

lib/Differentiator/ReverseModeVisitor.cpp

@@ -256,7 +256,6 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
                              const DiffRequest& request) {
     if (m_ExternalSource)
       m_ExternalSource->ActOnStartOfDerive();
-    silenceDiags = !request.VerboseDiags;
     assert(m_DiffReq == request);
 
     // FIXME: reverse mode plugins may have request mode other than
@@ -479,7 +478,6 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
     // for the two 'Derive's being different functions.
     if (m_ExternalSource)
       m_ExternalSource->ActOnStartOfDerive();
-    silenceDiags = !request.VerboseDiags;
     // FIXME: We should not use const_cast to get the decl request here.
     // NOLINTNEXTLINE(cppcoreguidelines-pro-type-const-cast)
     const_cast<DiffRequest&>(m_DiffReq) = request;
@@ -1943,8 +1941,7 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
                 CE->getNumArgs(), dfdx(), PreCallStmts, PostCallStmts,
                 DerivedCallArgs, CallArgDx);
           }
-          CallExprDiffDiagnostics(FD->getNameAsString(), CE->getBeginLoc(),
-                                  OverloadedDerivedFn);
+          CallExprDiffDiagnostics(FD, CE->getBeginLoc());
           if (!OverloadedDerivedFn) {
             Stmts& block = getCurrentBlock(direction::reverse);
             block.insert(block.begin(), PreCallStmts.begin(),

lib/Differentiator/VisitorBase.cpp

@@ -17,6 +17,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/TemplateBase.h"
+#include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/Lookup.h"
 #include "clang/Sema/Overload.h"
 #include "clang/Sema/Scope.h"
@@ -733,23 +734,28 @@ namespace clad {
         /*namespaceShouldExist=*/false);
   }
 
-  void VisitorBase::CallExprDiffDiagnostics(llvm::StringRef funcName,
-                                 SourceLocation srcLoc, bool isDerived){
-    if (!isDerived) {
-      // Function was not derived => issue a warning.
-      diag(DiagnosticsEngine::Warning,
-           srcLoc,
-           "function '%0' was not differentiated because clad failed to "
-           "differentiate it and no suitable overload was found in "
-           "namespace 'custom_derivatives', and function may not be "
-            "eligible for numerical differentiation.",
+  void VisitorBase::CallExprDiffDiagnostics(const clang::FunctionDecl* FD,
+                                            SourceLocation srcLoc) {
+    bool NumDiffEnabled =
+        !m_Sema.getPreprocessor().isMacroDefined("CLAD_NO_NUM_DIFF");
+    // FIXME: Switch to the real diagnostics engine and pass FD directly.
+    std::string funcName = FD->getNameAsString();
+    diag(DiagnosticsEngine::Warning, srcLoc,
+         "function '%0' was not differentiated because clad failed to "
+         "differentiate it and no suitable overload was found in "
+         "namespace 'custom_derivatives'",
+         {funcName});
+    if (NumDiffEnabled) {
+      diag(DiagnosticsEngine::Note, srcLoc,
+           "falling back to numerical differentiation for '%0' since no "
+           "suitable overload was found and clad could not derive it; "
+           "to disable this feature, compile your programs with "
+           "-DCLAD_NO_NUM_DIFF",
            {funcName});
     } else {
-      diag(DiagnosticsEngine::Warning, noLoc,
-           "Falling back to numerical differentiation for '%0' since no "
-           "suitable overload was found and clad could not derive it. "
-           "To disable this feature, compile your programs with "
-           "-DCLAD_NO_NUM_DIFF.",
+      diag(DiagnosticsEngine::Note, srcLoc,
+           "fallback to numerical differentiation is disabled by the "
+           "'CLAD_NO_NUM_DIFF' macro; considering '%0' as 0",
            {funcName});
     }
   }

test/Gradient/NonDifferentiableError.C

@@ -29,6 +29,12 @@ non_differentiable double fn_s2_mem_fn(double i, double j) {
   return obj.mem_fn(i, j) + i * j;
 }
 
+double no_body(double x); 
+
+double fn1(double x) { return no_body(x); } //expected-warning {{function 'no_body' was not differentiated}}
+//expected-note@34 {{fallback to numerical differentiation is disabled}}
+double fn2(double x) { return fn1(x); }
+
 #define INIT_EXPR(classname)                                                   \
   classname expr_1(2, 3);                                                      \
   classname expr_2(3, 5);
@@ -48,4 +54,5 @@ int main() {
   INIT_EXPR(SimpleFunctions2);
   TEST_CLASS(SimpleFunctions2, mem_fn, 3, 5);
   TEST_FUNC(fn_s2_mem_fn, 3, 5);  // expected-error {{attempted differentiation of function 'fn_s2_mem_fn', which is marked as non-differentiable}}
+  auto fn2_grad = clad::gradient(fn2);
 }

test/NumericalDiff/GradientMultiArg.C

@@ -1,6 +1,6 @@
-// RUN: %cladnumdiffclang %s -I%S/../../include -oGradientMultiArg.out 2>&1 | FileCheck -check-prefix=CHECK %s
+// RUN: %cladnumdiffclang %s -I%S/../../include -oGradientMultiArg.out -Xclang -verify 2>&1 | FileCheck -check-prefix=CHECK %s
 // RUN: ./GradientMultiArg.out | %filecheck_exec %s
-// RUN: %cladnumdiffclang -Xclang -plugin-arg-clad -Xclang -enable-tbr %s -I%S/../../include -oGradientMultiArg.out
+// RUN: %cladnumdiffclang -Xclang -plugin-arg-clad -Xclang -enable-tbr %s -I%S/../../include -oGradientMultiArg.out -Xclang -verify
 // RUN: ./GradientMultiArg.out | %filecheck_exec %s
 
 //CHECK-NOT: {{.*error|warning|note:.*}}
@@ -11,9 +11,9 @@
 #include <algorithm>
 
 double test_1(double x, double y){
-   return std::hypot(x, y);
+  return std::hypot(x, y); // expected-warning {{function 'hypot' was not differentiated}}
+  // expected-note@14 {{falling back to numerical differentiation}}
 }
-// CHECK: warning: Falling back to numerical differentiation for 'hypot' since no suitable overload was found and clad could not derive it. To disable this feature, compile your programs with -DCLAD_NO_NUM_DIFF.
 // CHECK: void test_1_grad(double x, double y, double *_d_x, double *_d_y) {
 // CHECK-NEXT:     {
 // CHECK-NEXT:         double _r0 = 0;

test/NumericalDiff/NoNumDiff.C

@@ -1,15 +1,14 @@
-// RUN: %cladclang %s -I%S/../../include -oNoNumDiff.out 2>&1 | FileCheck -check-prefix=CHECK %s
+// RUN: %cladclang %s -I%S/../../include -oNoNumDiff.out -Xclang -verify 2>&1 | FileCheck -check-prefix=CHECK %s
 
 //CHECK-NOT: {{.*error|warning|note:.*}}
 
 #include "clad/Differentiator/Differentiator.h"
 
 #include <cmath>
 
-double func(double x) { return std::tanh(x); }
+double func(double x) { return std::tanh(x); } // expected-warning 2{{function 'tanh' was not differentiated because clad failed to differentiate it and no suitable overload was found in namespace 'custom_derivatives'}}
+// expected-note@9 2{{fallback to numerical differentiation is disabled by the 'CLAD_NO_NUM_DIFF' macro}}
 
-//CHECK: warning: Numerical differentiation is diabled using the -DCLAD_NO_NUM_DIFF flag, this means that every try to numerically differentiate a function will fail! Remove the flag to revert to default behaviour.
-//CHECK: warning: Numerical differentiation is diabled using the -DCLAD_NO_NUM_DIFF flag, this means that every try to numerically differentiate a function will fail! Remove the flag to revert to default behaviour.
 //CHECK: double func_darg0(double x) {
 //CHECK-NEXT:     double _d_x = 1;
 //CHECK-NEXT:     return 0;
@@ -24,6 +23,6 @@ double func(double x) { return std::tanh(x); }
 
 
 int main(){
-    clad::differentiate(func, "x");
-    clad::gradient(func);
+  clad::differentiate(func, "x");
+  clad::gradient(func);
 }

test/NumericalDiff/NumDiff.C

@@ -1,15 +1,14 @@
-// RUN: %cladnumdiffclang %s -I%S/../../include -oNumDiff.out 2>&1 | FileCheck -check-prefix=CHECK %s
+// RUN: %cladnumdiffclang %s -I%S/../../include -oNumDiff.out -Xclang -verify 2>&1 | FileCheck -check-prefix=CHECK %s
 // RUN: ./NumDiff.out | %filecheck_exec %s
-// RUN: %cladnumdiffclang -Xclang -plugin-arg-clad -Xclang -enable-tbr %s -I%S/../../include -oNumDiff.out
+// RUN: %cladnumdiffclang -Xclang -plugin-arg-clad -Xclang -enable-tbr -Xclang -verify %s -I%S/../../include -oNumDiff.out
 // RUN: ./NumDiff.out | %filecheck_exec %s
 //CHECK-NOT: {{.*error|warning|note:.*}}
 #include "clad/Differentiator/Differentiator.h"
 
 double test_1(double x){
-   return tanh(x);
+  return tanh(x); // expected-warning {{function 'tanh' was not differentiated because clad failed to differentiate it and no suitable overload was found in namespace 'custom_derivatives'}}
+  // expected-note@9 {{falling back to numerical differentiation for 'tanh'}}
 }
-//CHECK: warning: Falling back to numerical differentiation for 'tanh' since no suitable overload was found and clad could not derive it. To disable this feature, compile your programs with -DCLAD_NO_NUM_DIFF.
-//CHECK: warning: Falling back to numerical differentiation for 'log10' since no suitable overload was found and clad could not derive it. To disable this feature, compile your programs with -DCLAD_NO_NUM_DIFF.
 
 //CHECK: void test_1_grad(double x, double *_d_x) {
 //CHECK-NEXT:     {
@@ -21,7 +20,8 @@ double test_1(double x){
 
 
 double test_2(double x){
-   return std::log10(x);
+   return std::log10(x);// expected-warning {{function 'log10' was not differentiated because clad failed to differentiate it and no suitable overload was found in namespace 'custom_derivatives'}}
+  // expected-note@23 {{falling back to numerical differentiation for 'log10'}}
 }
 //CHECK: double test_2_darg0(double x) {
 //CHECK-NEXT:     double _d_x = 1;
@@ -32,7 +32,8 @@ double test_2(double x){
 double test_3(double x) {
     if (x > 0) {
         double constant = 11.;
-        return std::hypot(x, constant);
+        return std::hypot(x, constant); // expected-warning {{function 'hypot' was not differentiated because clad failed to differentiate it and no suitable overload was found in namespace 'custom_derivatives'}}
+  // expected-note@35 {{falling back to numerical differentiation for 'hypot'}}
     }
     return 0;
 }

test/NumericalDiff/PrintErrorNumDiff.C

@@ -1,6 +1,6 @@
-// RUN: %cladnumdiffclang -Xclang -plugin-arg-clad -Xclang -fprint-num-diff-errors %s -I%S/../../include -oPrintErrorNumDiff.out 2>&1 | FileCheck -check-prefix=CHECK %s
+// RUN: %cladnumdiffclang -Xclang -plugin-arg-clad -Xclang -fprint-num-diff-errors %s -I%S/../../include -oPrintErrorNumDiff.out -Xclang -verify 2>&1 | FileCheck -check-prefix=CHECK %s
 // RUN: ./PrintErrorNumDiff.out | %filecheck_exec %s
-// RUN: %cladnumdiffclang -Xclang -plugin-arg-clad -Xclang -fprint-num-diff-errors -Xclang -plugin-arg-clad -Xclang -enable-tbr %s -I%S/../../include -oPrintErrorNumDiff.out
+// RUN: %cladnumdiffclang -Xclang -plugin-arg-clad -Xclang -fprint-num-diff-errors -Xclang -plugin-arg-clad -Xclang -enable-tbr %s -I%S/../../include -oPrintErrorNumDiff.out -Xclang -verify
 // RUN: ./PrintErrorNumDiff.out | %filecheck_exec %s
 
 //CHECK-NOT: {{.*error|warning|note:.*}}
@@ -12,10 +12,10 @@
 extern "C" int printf(const char* fmt, ...);
 
 double test_1(double x){
-   return tanh(x);
+  return tanh(x); // expected-warning {{function 'tanh' was not differentiated because}}
+  // expected-note@15 {{falling back to numerical differentiation for 'tanh}}
 }
 
-//CHECK: warning: Falling back to numerical differentiation for 'tanh' since no suitable overload was found and clad could not derive it. To disable this feature, compile your programs with -DCLAD_NO_NUM_DIFF.
 //CHECK: void test_1_grad(double x, double *_d_x) {
 //CHECK-NEXT:     {
 //CHECK-NEXT:         double _r0 = 0;