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Format function arg defaults from their source text #1069

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40 changes: 27 additions & 13 deletions lib/CppInterOp/CppInterOp.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,7 @@
#include "clang/Basic/Version.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Interpreter/Interpreter.h"
#include "clang/Lex/Lexer.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/Overload.h"
#include "clang/Sema/Ownership.h"
Expand Down Expand Up @@ -5485,6 +5486,32 @@ std::string GetFunctionArgDefault(ConstFuncRef func, size_t param_index) {
PI = (FD->getTemplatedDecl())->getNonObjectParameter(param_index);

if (PI->hasDefaultArg()) {
// Render the default as written: read its source range, the way clang's
// own code completion formats default arguments (GetDefaultValueString
// in SemaCodeComplete). Pretty-printing the AST instead reproduces
// floating literals at representation precision ("3.1400000000000001"
// for a written 3.14), and normalizing that through std::stod terminated
// the exception-free build on symbolic defaults such as
// `double ratio = kDefaultRatio`.
Sema& S = getSema();
CharSourceRange SrcRange =
CharSourceRange::getTokenRange(PI->getDefaultArgRange());
bool Invalid = SrcRange.isInvalid();
if (!Invalid) {
llvm::StringRef SrcText = Lexer::getSourceText(
SrcRange, S.getSourceManager(), S.getLangOpts(), &Invalid);
if (!Invalid) {
// The lexed range sometimes includes the leading '=' (see the FIXME
// in SemaCodeComplete's GetDefaultValueString); keep only the value.
SrcText = SrcText.ltrim();
SrcText.consume_front("=");
SrcText = SrcText.ltrim();
if (!SrcText.empty())
return INTEROP_RETURN(SrcText.str());
}
}

// Fallback for defaults with no usable source range: print the AST.
std::string Result;
llvm::raw_string_ostream OS(Result);
const Expr* DefaultArgExpr = nullptr;
Expand All @@ -5494,19 +5521,6 @@ std::string GetFunctionArgDefault(ConstFuncRef func, size_t param_index) {
else
DefaultArgExpr = PI->getDefaultArg();
DefaultArgExpr->printPretty(OS, nullptr, PrintingPolicy(LangOptions()));

// FIXME: Floats are printed in clang with the precision of their underlying
// representation and not as written. This is a deficiency in the printing
// mechanism of clang which we require extra work to mitigate. For example
// float PI = 3.14 is printed as 3.1400000000000001
if (PI->getType()->isFloatingType()) {
if (!Result.empty() && Result.back() == '.')
return INTEROP_RETURN(Result);
auto DefaultArgValue = std::stod(Result);
std::ostringstream oss;
oss << DefaultArgValue;
Result = oss.str();
}
return INTEROP_RETURN(Result);
}
return INTEROP_RETURN("");
Expand Down
30 changes: 27 additions & 3 deletions unittests/CppInterOp/FunctionReflectionTest.cpp
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Expand Up @@ -2870,10 +2870,10 @@ TYPED_TEST(CPPINTEROP_TEST_MODE, FunctionReflection_GetFunctionArgDefault) {
GetAllTopLevelDecls(code, Decls);

EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[0], 0), "");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[0], 1), "4.");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[0], 1), "4.0");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[0], 2), "\"default\"");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[0], 3), "\'c\'");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[1], 0), "0.");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[1], 0), "0.0");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[1], 1), "3.123");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[1], 2), "34126");

Expand All @@ -2888,7 +2888,7 @@ TYPED_TEST(CPPINTEROP_TEST_MODE, FunctionReflection_GetFunctionArgDefault) {
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[4], 0), "");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[4], 1), "");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[4], 2), "\'a\'");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[4], 3), "0.");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[4], 3), "0.0");

ASTContext& C = Interp->getCI()->getASTContext();
std::vector<Cpp::TemplateArgInfo> template_args = {C.IntTy.getAsOpaquePtr()};
Expand All @@ -2903,6 +2903,30 @@ TYPED_TEST(CPPINTEROP_TEST_MODE, FunctionReflection_GetFunctionArgDefault) {
EXPECT_EQ(Cpp::GetFunctionArgDefault(fn, 1), "S()");
}

TYPED_TEST(CPPINTEROP_TEST_MODE,
FunctionReflection_GetFunctionArgDefaultSymbolic) {
std::vector<Decl*> Decls;
std::string code = R"(
constexpr double kDefaultRatio = 0.5;
double default_ratio();
double scaled(double ratio = kDefaultRatio);
double rescaled(double ratio = default_ratio());
double inverted(double ratio = 2.0 / kDefaultRatio);
double pi_ish(double p = 3.14);
)";

GetAllTopLevelDecls(code, Decls);

// A floating-typed default need not be a numeric literal. Formatting a
// symbolic default must not crash (the removed std::stod normalization
// terminated the exception-free build) and must render it as written.
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[2], 0), "kDefaultRatio");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[3], 0), "default_ratio()");
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[4], 0), "2.0 / kDefaultRatio");
// Literals render exactly as written, not at representation precision.
EXPECT_EQ(Cpp::GetFunctionArgDefault(Decls[5], 0), "3.14");
}

TYPED_TEST(CPPINTEROP_TEST_MODE, FunctionReflection_Construct) {
#ifdef _WIN32
GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
Expand Down
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