fix Issue 23509 - ImportC: need statement expressions extension for GLibC's assert() (#15093)

compiler/src/dmd/cparse.d

@@ -799,7 +799,10 @@ final class CParser(AST) : Parser!AST
 
         case TOK.leftParenthesis:
             nextToken();
-            e = cparseExpression();
+            if (token.value == TOK.leftCurly)
+                e = cparseStatementExpression();        // gcc extension
+            else
+                e = cparseExpression();
             check(TOK.rightParenthesis);
             break;
 
@@ -1622,6 +1625,41 @@ final class CParser(AST) : Parser!AST
         return e;
     }
 
+    /*****************************
+     * gcc extension: https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
+     * Represent as a function literal, then call the function literal.
+     * Parser is on opening curly brace.
+     */
+    private AST.Expression cparseStatementExpression()
+    {
+        AST.ParameterList parameterList;
+        StorageClass stc = 0;
+        const loc = token.loc;
+        typedefTab.push(null);
+        auto fbody = cparseStatement(ParseStatementFlags.scope_);
+        typedefTab.pop();                                        // end of function scope
+
+        // Rewrite last ExpStatement (if there is one) as a ReturnStatement
+        auto ss = fbody.isScopeStatement();
+        auto cs = ss.statement.isCompoundStatement();
+        assert(cs);
+        if (const len = (*cs.statements).length)
+        {
+            auto s = (*cs.statements)[len - 1];
+            if (auto es = s.isExpStatement())
+                (*cs.statements)[len - 1] = new AST.ReturnStatement(es.loc, es.exp);
+        }
+
+        auto tf = new AST.TypeFunction(parameterList, null, LINK.d, stc);
+        auto fd = new AST.FuncLiteralDeclaration(loc, token.loc, tf, TOK.delegate_, null, null, 0);
+        fd.fbody = fbody;
+
+        auto fe = new AST.FuncExp(loc, fd);
+        auto args = new AST.Expressions();
+        auto e = new AST.CallExp(loc, fe, args);   // call the function literal
+        return e;
+    }
+
     //}
     /********************************************************************************/
     /********************************* Declaration Parser ***************************/

compiler/src/dmd/hdrgen.d

@@ -196,10 +196,9 @@ private void statementToBuffer(Statement s, OutBuffer* buf, HdrGenState* hgs)
         foreach (sx; *s.statements)
         {
             auto ds = sx ? sx.isExpStatement() : null;
-            if (ds && ds.exp.op == EXP.declaration)
+            if (ds && ds.exp.isDeclarationExp())
             {
-                auto d = (cast(DeclarationExp)ds.exp).declaration;
-                assert(d.isDeclaration());
+                auto d = ds.exp.isDeclarationExp().declaration;
                 if (auto v = d.isVarDeclaration())
                 {
                     scope ppv = new DsymbolPrettyPrintVisitor(buf, hgs);

compiler/test/compilable/test23509.i

@@ -0,0 +1,8 @@
+// https://issues.dlang.org/show_bug.cgi?id=23509
+
+int max(int a, int b)
+{
+    return ({int _a = (a), _b = (b); _a > _b ? _a : _b; });
+}
+
+_Static_assert(max(3,4) == 4, "1");