C++: Add a skeleton class for requires expressions

cpp/downgrades/6f5d51e89e762fe4609fd4ac8ee3afb04221e873/exprs.ql

@@ -0,0 +1,15 @@
+class Expr extends @expr {
+  string toString() { none() }
+}
+
+class Location extends @location_expr {
+  string toString() { none() }
+}
+
+predicate isExprRequires(Expr expr) { exists(int kind | exprs(expr, kind, _) | kind = 390) }
+
+from Expr expr, int kind, int kind_new, Location location
+where
+  exprs(expr, kind, location) and
+  if isExprRequires(expr) then kind_new = 1 else kind_new = kind
+select expr, kind_new, location

cpp/downgrades/6f5d51e89e762fe4609fd4ac8ee3afb04221e873/upgrade.properties

@@ -0,0 +1,3 @@
+description: Add requires expr
+compatibility: partial
+exprs.rel: run exprs.qlo

cpp/ql/lib/cpp.qll

@@ -17,6 +17,7 @@ import semmle.code.cpp.File
 import semmle.code.cpp.Linkage
 import semmle.code.cpp.Location
 import semmle.code.cpp.Compilation
+import semmle.code.cpp.Concept
 import semmle.code.cpp.Element
 import semmle.code.cpp.Namespace
 import semmle.code.cpp.Specifier

cpp/ql/lib/semmle/code/cpp/Concept.qll

@@ -0,0 +1,14 @@
+/**
+ * Provides classes for working with C++ concepts.
+ */
+
+import semmle.code.cpp.exprs.Expr
+
+/**
+ * A C/C++ requires expression.
+ */
+class RequiresExpr extends Expr, @requires_expr {
+  override string toString() { result = "requires ..." }
+
+  override string getAPrimaryQlClass() { result = "RequiresExpr" }
+}

cpp/ql/lib/semmlecode.cpp.dbscheme

@@ -1790,6 +1790,7 @@ case @expr.kind of
 | 387 = @istriviallyrelocatable
 | 388 = @datasizeof
 | 389 = @c11_generic
+| 390 = @requires_expr
 ;
 
 @var_args_expr = @vastartexpr

cpp/ql/lib/upgrades/7ff6a6e53dbcff09d1b9b758b594bc6d17366863/upgrade.properties

@@ -0,0 +1,2 @@
+description: Add requires expressions
+compatibility: full

cpp/ql/test/library-tests/ir/ir/PrintAST.expected

@@ -23564,6 +23564,26 @@ ir.cpp:
 # 2686|           Value = [CStyleCast] 0
 # 2686|           ValueCategory = prvalue
 # 2687|     getStmt(1): [ReturnStmt] return ...
+# 2691| [TopLevelFunction] int concepts::requires_use()
+# 2691|   <params>: 
+# 2691|   getEntryPoint(): [BlockStmt] { ... }
+# 2692|     getStmt(0): [DeclStmt] declaration
+# 2692|       getDeclarationEntry(0): [VariableDeclarationEntry] definition of y
+# 2692|           Type = [IntType] int
+# 2692|         getVariable().getInitializer(): [Initializer] initializer for y
+#-----|           getExpr(): [RequiresExpr] requires ...
+#-----|               Type = [BoolType] bool
+#-----|               Value = [RequiresExpr] 1
+#-----|               ValueCategory = prvalue
+#-----|           getExpr().getFullyConverted(): [CStyleCast] (int)...
+#-----|               Conversion = [IntegralConversion] integral conversion
+#-----|               Type = [IntType] int
+#-----|               Value = [CStyleCast] 1
+#-----|               ValueCategory = prvalue
+# 2693|     getStmt(1): [ReturnStmt] return ...
+# 2693|       getExpr(): [VariableAccess] y
+# 2693|           Type = [IntType] int
+# 2693|           ValueCategory = prvalue(load)
 many-defs-per-use.cpp:
 #   34| [TopLevelFunction] void many_defs_per_use()
 #   34|   <params>: 

cpp/ql/test/library-tests/ir/ir/aliased_ir.expected

@@ -19099,6 +19099,24 @@ ir.cpp:
 # 2684|   Block 8
 # 2684|     v2684_14(void) = Unreached : 
 
+# 2691| int concepts::requires_use()
+# 2691|   Block 0
+# 2691|     v2691_1(void)       = EnterFunction            : 
+# 2691|     m2691_2(unknown)    = AliasedDefinition        : 
+# 2691|     m2691_3(unknown)    = InitializeNonLocal       : 
+# 2691|     m2691_4(unknown)    = Chi                      : total:m2691_2, partial:m2691_3
+# 2692|     r2692_1(glval<int>) = VariableAddress[y]       : 
+#-----|     r0_1(int)           = Constant[1]              : 
+#-----|     m0_2(int)           = Store[y]                 : &:r2692_1, r0_1
+# 2693|     r2693_1(glval<int>) = VariableAddress[#return] : 
+# 2693|     r2693_2(glval<int>) = VariableAddress[y]       : 
+# 2693|     r2693_3(int)        = Load[y]                  : &:r2693_2, m0_2
+# 2693|     m2693_4(int)        = Store[#return]           : &:r2693_1, r2693_3
+# 2691|     r2691_5(glval<int>) = VariableAddress[#return] : 
+# 2691|     v2691_6(void)       = ReturnValue              : &:r2691_5, m2693_4
+# 2691|     v2691_7(void)       = AliasedUse               : m2691_3
+# 2691|     v2691_8(void)       = ExitFunction             : 
+
 many-defs-per-use.cpp:
 #   34| void many_defs_per_use()
 #   34|   Block 0

cpp/ql/test/library-tests/ir/ir/ir.cpp

@@ -2686,4 +2686,13 @@ void test(bool b)
   twice_call_use(b ? "" : "");
 }
 
+namespace concepts {
+
+int requires_use() {
+  int y = requires { sizeof(int) > 0; };
+  return y;
+}
+
+}
+
 // semmle-extractor-options: -std=c++20 --clang

cpp/ql/test/library-tests/ir/ir/raw_ir.expected

@@ -17422,6 +17422,23 @@ ir.cpp:
 # 2684|     v2684_7(void) = AliasedUse   : ~m?
 # 2684|     v2684_8(void) = ExitFunction : 
 
+# 2691| int concepts::requires_use()
+# 2691|   Block 0
+# 2691|     v2691_1(void)       = EnterFunction            : 
+# 2691|     mu2691_2(unknown)   = AliasedDefinition        : 
+# 2691|     mu2691_3(unknown)   = InitializeNonLocal       : 
+# 2692|     r2692_1(glval<int>) = VariableAddress[y]       : 
+#-----|     r0_1(int)           = Constant[1]              : 
+#-----|     mu0_2(int)          = Store[y]                 : &:r2692_1, r0_1
+# 2693|     r2693_1(glval<int>) = VariableAddress[#return] : 
+# 2693|     r2693_2(glval<int>) = VariableAddress[y]       : 
+# 2693|     r2693_3(int)        = Load[y]                  : &:r2693_2, ~m?
+# 2693|     mu2693_4(int)       = Store[#return]           : &:r2693_1, r2693_3
+# 2691|     r2691_4(glval<int>) = VariableAddress[#return] : 
+# 2691|     v2691_5(void)       = ReturnValue              : &:r2691_4, ~m?
+# 2691|     v2691_6(void)       = AliasedUse               : ~m?
+# 2691|     v2691_7(void)       = ExitFunction             : 
+
 many-defs-per-use.cpp:
 #   34| void many_defs_per_use()
 #   34|   Block 0