ImportC: Add test for function-like macro calling another macro (#22349)

* ImportC: Add test for function-like macro calling another macro

Tests the `if (params) break;` branch in TOK.identifier case,
ensuring function-like macros with identifier bodies are handled
by caseFunctionLike, not the new nullary template path.

* ImportC: Replace unreachable branch with assertion

When we reach TOK.identifier case, params is always false because
if params were true (macro name followed by '('), the next token
would be TOK.leftParenthesis, not TOK.identifier.

Author: CyberShadow

compiler/src/dmd/cparse.d

@@ -5779,8 +5779,7 @@ final class CParser(AST) : Parser!AST
                              * Rewrite to a template function:
                              *  auto ID()() { return identifier(args); }
                              */
-                            if (params)
-                                break;                          // function-like macro with params handled elsewhere
+                            assert(!params);                    // would be TOK.leftParenthesis
                             eLatch.sawErrors = false;
                             auto exp = cparseExpression();
                             if (eLatch.sawErrors)               // parsing errors

compiler/test/compilable/imports/defines.c

@@ -68,3 +68,4 @@ int pr16199c()
 #define DOUBLE(x) ((x) * 2)
 #define BARE_CALL DOUBLE(5)          // bare function-like macro call (no outer parens)
 #define PAREN_CALL (DOUBLE(5))       // parenthesized call (already works)
+#define WRAPPER(x) DOUBLE(x)         // function-like macro calling another macro

compiler/test/compilable/testdefines.d

@@ -44,3 +44,4 @@ static assert(is(typeof(NEGATIVE_F64) == double));
 static assert(DOUBLE(5) == 10);
 static assert(BARE_CALL == 10);      // bare call now works
 static assert(PAREN_CALL == 10);     // parenthesized already worked
+static assert(WRAPPER(3) == 6);      // function-like macro calling another macro