Translate concepts and requires expressions (#347)

They are evaluated by clang. Only the result of the evaluation is
translated.

Furthermore, static_assert is no-op because it's evaluated at compile
time. Same for concept declaration.

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -1284,6 +1284,27 @@ bool Converter::VisitTypeAliasTemplateDecl(clang::TypeAliasTemplateDecl *) {
   return false;
 }
 
+bool Converter::VisitStaticAssertDecl(clang::StaticAssertDecl *decl) {
+  auto *assert_expr = decl->getAssertExpr();
+  if (assert_expr->isValueDependent()) {
+    return false;
+  }
+  std::string condition;
+  if (assert_expr->getType()->isBooleanType() &&
+      IsRustConstEvaluableExpr(assert_expr)) {
+    condition = ToString(assert_expr);
+  } else {
+    bool value = false;
+    ENSURE(assert_expr->EvaluateAsBooleanCondition(value, ctx_));
+    condition = value ? keyword::kTrue : keyword::kFalse;
+  }
+  StrCat(std::format("const _: () = assert!({}{});", condition,
+                     GetAssertMessageAsString(assert_expr, ctx_)));
+  return false;
+}
+
+bool Converter::VisitConceptDecl(clang::ConceptDecl *) { return false; }
+
 static bool IsaSemiColonStmt(const clang::Stmt *stmt) {
   switch (stmt->getStmtClass()) {
   case clang::Stmt::IfStmtClass:
@@ -2275,30 +2296,6 @@ bool Converter::VisitCharacterLiteral(clang::CharacterLiteral *expr) {
   return false;
 }
 
-std::string Converter::GetEscapedCharLiteral(char character) const {
-  switch (character) {
-  case '"':
-    return "\\\"";
-  case '\'':
-    return "\\'";
-  case '\\':
-    return "\\\\";
-  case '\n':
-    return "\\n";
-  case '\r':
-    return "\\r";
-  case '\t':
-    return "\\t";
-  case '\0':
-    return "\\0";
-  }
-  auto uc = static_cast<unsigned char>(character);
-  if (uc < 0x20 || uc >= 0x7F) {
-    return std::format("\\x{:02x}", uc);
-  }
-  return std::string(1, character);
-}
-
 std::string Converter::GetEscapedUTF8CharLiteral(clang::Expr *expr) const {
   auto char_expr =
       clang::dyn_cast<clang::CharacterLiteral>(expr->IgnoreCasts());
@@ -3718,6 +3715,21 @@ bool Converter::VisitUnaryExprOrTypeTraitExpr(
   return false;
 }
 
+bool Converter::VisitConceptSpecializationExpr(
+    clang::ConceptSpecializationExpr *expr) {
+  assert(!expr->isValueDependent());
+  StrCat(expr->isSatisfied() ? keyword::kTrue : keyword::kFalse);
+  computed_expr_type_ = ComputedExprType::FreshValue;
+  return false;
+}
+
+bool Converter::VisitRequiresExpr(clang::RequiresExpr *expr) {
+  assert(!expr->isValueDependent());
+  StrCat(expr->isSatisfied() ? keyword::kTrue : keyword::kFalse);
+  computed_expr_type_ = ComputedExprType::FreshValue;
+  return false;
+}
+
 bool Converter::VisitTypeTraitExpr(clang::TypeTraitExpr *expr) {
   clang::Expr::EvalResult result;
   ENSURE(expr->EvaluateAsInt(result, ctx_));

cpp2rust/converter/converter.h

@@ -178,6 +178,9 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
   virtual bool VisitTypeAliasDecl(clang::TypeAliasDecl *decl);
   virtual bool VisitTypeAliasTemplateDecl(clang::TypeAliasTemplateDecl *decl);
 
+  bool VisitStaticAssertDecl(clang::StaticAssertDecl *decl);
+  bool VisitConceptDecl(clang::ConceptDecl *decl);
+
   virtual bool VisitCompoundStmt(clang::CompoundStmt *stmt);
 
   virtual bool VisitDeclStmt(clang::DeclStmt *stmt);
@@ -365,7 +368,6 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
 
   virtual bool VisitCharacterLiteral(clang::CharacterLiteral *expr);
 
-  std::string GetEscapedCharLiteral(char character) const;
   std::string GetCodeUnitArrayLiteral(const clang::StringLiteral *expr);
   bool IsArrayInitContext() const;
 
@@ -441,6 +443,10 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
 
   virtual bool VisitSizeOfPackExpr(clang::SizeOfPackExpr *expr);
 
+  virtual bool
+  VisitConceptSpecializationExpr(clang::ConceptSpecializationExpr *expr);
+  virtual bool VisitRequiresExpr(clang::RequiresExpr *expr);
+
   virtual bool VisitOffsetOfExpr(clang::OffsetOfExpr *expr);
 
   virtual bool VisitEnumDecl(clang::EnumDecl *decl);

cpp2rust/converter/converter_lib.cpp

@@ -5,9 +5,11 @@
 
 #include <clang/AST/DeclTemplate.h>
 #include <clang/AST/ExprCXX.h>
+#include <clang/AST/ExprConcepts.h>
 #include <clang/AST/Mangle.h>
 #include <clang/AST/ParentMapContext.h>
 #include <clang/Basic/SourceManager.h>
+#include <clang/Lex/Lexer.h>
 #include <clang/Sema/Initialization.h>
 #include <clang/Sema/Sema.h>
 #include <llvm/Support/ErrorHandling.h>
@@ -111,6 +113,67 @@ bool IsBuiltinConstantP(const clang::Expr *expr) {
   return false;
 }
 
+bool IsRustConstEvaluableExpr(const clang::Expr *expr) {
+  expr = expr->IgnoreParenImpCasts();
+  if (clang::isa<clang::IntegerLiteral, clang::ConceptSpecializationExpr>(
+          expr)) {
+    return true;
+  }
+  if (auto *trait = clang::dyn_cast<clang::UnaryExprOrTypeTraitExpr>(expr)) {
+    return trait->getKind() == clang::UnaryExprOrTypeTrait::UETT_SizeOf;
+  }
+  if (auto *unary = clang::dyn_cast<clang::UnaryOperator>(expr)) {
+    return unary->getOpcode() == clang::UO_LNot &&
+           IsRustConstEvaluableExpr(unary->getSubExpr());
+  }
+  if (auto *binary = clang::dyn_cast<clang::BinaryOperator>(expr)) {
+    return (binary->isEqualityOp() || binary->isRelationalOp()) &&
+           IsRustConstEvaluableExpr(binary->getLHS()) &&
+           IsRustConstEvaluableExpr(binary->getRHS());
+  }
+  return false;
+}
+
+std::string GetEscapedCharLiteral(char character) {
+  switch (character) {
+  case '"':
+    return "\\\"";
+  case '\'':
+    return "\\'";
+  case '\\':
+    return "\\\\";
+  case '\n':
+    return "\\n";
+  case '\r':
+    return "\\r";
+  case '\t':
+    return "\\t";
+  case '\0':
+    return "\\0";
+  }
+  auto uc = static_cast<unsigned char>(character);
+  if (uc < 0x20 || uc >= 0x7F) {
+    return std::format("\\x{:02x}", uc);
+  }
+  return std::string(1, character);
+}
+
+std::string GetAssertMessageAsString(const clang::Expr *expr,
+                                     const clang::ASTContext &ctx) {
+  auto text = clang::Lexer::getSourceText(
+      clang::CharSourceRange::getTokenRange(expr->getSourceRange()),
+      ctx.getSourceManager(), ctx.getLangOpts());
+  std::string message = R"(, ")";
+  for (char c : text) {
+    // Doubled so that assert! does not read them as a format placeholder.
+    if (c == '{' || c == '}') {
+      message += c;
+    }
+    message += GetEscapedCharLiteral(c);
+  }
+  return message + '"';
+}
+
 bool IsComparisonWithNullOp(const clang::BinaryOperator *expr) {
   if (!expr->isComparisonOp()) {
     return false;

cpp2rust/converter/converter_lib.h

@@ -42,6 +42,13 @@ bool IsGlobalVar(const clang::VarDecl *decl);
 
 bool IsGlobalVar(const clang::Expr *expr);
 
+bool IsRustConstEvaluableExpr(const clang::Expr *expr);
+
+std::string GetEscapedCharLiteral(char character);
+
+std::string GetAssertMessageAsString(const clang::Expr *expr,
+                                     const clang::ASTContext &ctx);
+
 bool IsComparisonWithNullOp(const clang::BinaryOperator *expr);
 
 bool IsInMainFile(const clang::Decl *decl);

tests/unit/concepts.cpp

@@ -0,0 +1,45 @@
+// ADDITIONAL_COMPILE_FLAGS: -std=c++20
+#include <cassert>
+#include <concepts>
+
+template <typename T>
+concept Small = sizeof(T) <= 4;
+
+static_assert(Small<int>);
+static_assert(sizeof(int) == 4);
+
+template <typename T>
+concept HasSize = requires(T t) {
+  { t.size() } -> std::same_as<int>;
+};
+
+struct Sized {
+  int size() { return 4; }
+};
+
+template <typename T> bool is_small() { return Small<T>; }
+
+template <typename T> bool has_size() {
+  return requires(T t) { t.size(); };
+}
+
+template <typename T> int pick(T x) {
+  if (std::integral<T> && Small<T>) {
+    return 1;
+  }
+  return 2;
+}
+
+int main() {
+  static_assert(!Small<long>);
+  assert(is_small<char>());
+  assert(!is_small<double>());
+  assert(HasSize<Sized>);
+  assert(!HasSize<int>);
+  assert(has_size<Sized>());
+  assert(!has_size<int>());
+  assert(pick(1) == 1);
+  assert(pick(1L) == 2);
+  assert(pick(1.0f) == 2);
+  return 0;
+}

tests/unit/out/refcount/concepts.rs

@@ -0,0 +1,74 @@
+extern crate libcc2rs;
+use libcc2rs::*;
+use std::cell::RefCell;
+use std::collections::BTreeMap;
+use std::io::prelude::*;
+use std::io::{Read, Seek, Write};
+use std::os::fd::AsFd;
+use std::rc::{Rc, Weak};
+const _: () = assert!(true, "Small<int>");
+const _: () = assert!(
+    (::std::mem::size_of::<i32>() == 4_usize),
+    "sizeof(int) == 4"
+);
+#[derive(Clone, ByteRepr, Default)]
+pub struct Sized {}
+pub fn is_small_0() -> bool {
+    return true;
+}
+pub fn is_small_1() -> bool {
+    return false;
+}
+pub fn has_size_2() -> bool {
+    return true;
+}
+pub fn has_size_3() -> bool {
+    return false;
+}
+pub fn pick_4(x: i32) -> i32 {
+    let x: Value<i32> = Rc::new(RefCell::new(x));
+    if (true) && (true) {
+        return 1;
+    }
+    return 2;
+}
+pub fn pick_5(x: i64) -> i32 {
+    let x: Value<i64> = Rc::new(RefCell::new(x));
+    if (true) && (false) {
+        return 1;
+    }
+    return 2;
+}
+pub fn pick_6(x: f32) -> i32 {
+    let x: Value<f32> = Rc::new(RefCell::new(x));
+    if (false) && (true) {
+        return 1;
+    }
+    return 2;
+}
+pub fn main() {
+    __cpp2rust_init_globals();
+    std::process::exit(main_0());
+}
+fn main_0() -> i32 {
+    const _: () = assert!(!(false), "!Small<long>");;
+    assert!(({ is_small_0() }));
+    assert!(!({ is_small_1() }));
+    assert!(true);
+    assert!(!(false));
+    assert!(({ has_size_2() }));
+    assert!(!({ has_size_3() }));
+    assert!((({ pick_4(1,) }) == 1));
+    assert!((({ pick_5(1_i64,) }) == 2));
+    assert!((({ pick_6(1.0E+0,) }) == 2));
+    return 0;
+}
+pub trait SizedImpl {
+    fn size(&self) -> i32;
+}
+impl SizedImpl for Ptr<Sized> {
+    fn size(&self) -> i32 {
+        return 4;
+    }
+}
+pub fn __cpp2rust_init_globals() {}

tests/unit/out/unsafe/concepts.rs

@@ -0,0 +1,71 @@
+extern crate libc;
+use libc::*;
+extern crate libcc2rs;
+use libcc2rs::*;
+use std::collections::BTreeMap;
+use std::io::{Read, Seek, Write};
+use std::os::fd::{AsFd, FromRawFd, IntoRawFd};
+use std::rc::Rc;
+const _: () = assert!(true, "Small<int>");
+const _: () = assert!(
+    ((::std::mem::size_of::<i32>()) == (4_usize)),
+    "sizeof(int) == 4"
+);
+#[repr(C)]
+#[derive(Copy, Clone, Default)]
+pub struct Sized {}
+impl Sized {
+    pub unsafe fn size(&mut self) -> i32 {
+        return 4;
+    }
+}
+pub unsafe fn is_small_0() -> bool {
+    return true;
+}
+pub unsafe fn is_small_1() -> bool {
+    return false;
+}
+pub unsafe fn has_size_2() -> bool {
+    return true;
+}
+pub unsafe fn has_size_3() -> bool {
+    return false;
+}
+pub unsafe fn pick_4(mut x: i32) -> i32 {
+    if (true) && (true) {
+        return 1;
+    }
+    return 2;
+}
+pub unsafe fn pick_5(mut x: i64) -> i32 {
+    if (true) && (false) {
+        return 1;
+    }
+    return 2;
+}
+pub unsafe fn pick_6(mut x: f32) -> i32 {
+    if (false) && (true) {
+        return 1;
+    }
+    return 2;
+}
+pub fn main() {
+    unsafe {
+        __cpp2rust_init_globals();
+        std::process::exit(main_0() as i32);
+    }
+}
+unsafe fn main_0() -> i32 {
+    const _: () = assert!(!(false), "!Small<long>");;
+    assert!((unsafe { is_small_0() }));
+    assert!(!(unsafe { is_small_1() }));
+    assert!(true);
+    assert!(!(false));
+    assert!((unsafe { has_size_2() }));
+    assert!(!(unsafe { has_size_3() }));
+    assert!(((unsafe { pick_4(1,) }) == (1)));
+    assert!(((unsafe { pick_5(1_i64,) }) == (2)));
+    assert!(((unsafe { pick_6(1.0E+0,) }) == (2)));
+    return 0;
+}
+pub unsafe fn __cpp2rust_init_globals() {}