Implement macro expansion in IfExpr, IfExprConseqElse, IfExprConseqIf, IfExprConseqIfLet.

Addresses #1141

Author: antego

gcc/rust/expand/rust-attribute-visitor.cc

@@ -1630,6 +1630,9 @@ AttrVisitor::visit (AST::IfExpr &expr)
   // can't strip condition expr itself, but can strip sub-expressions
   auto &condition_expr = expr.get_condition_expr ();
   condition_expr->accept_vis (*this);
+  auto cond_fragment = expander.take_expanded_fragment (*this);
+  if (cond_fragment.should_expand ())
+    condition_expr = cond_fragment.take_expression_fragment ();
   if (condition_expr->is_marked_for_strip ())
     rust_error_at (condition_expr->get_locus (),
 		   "cannot strip expression in this position - outer "
@@ -1657,6 +1660,9 @@ AttrVisitor::visit (AST::IfExprConseqElse &expr)
   // can't strip condition expr itself, but can strip sub-expressions
   auto &condition_expr = expr.get_condition_expr ();
   condition_expr->accept_vis (*this);
+  auto cond_fragment = expander.take_expanded_fragment (*this);
+  if (cond_fragment.should_expand ())
+    condition_expr = cond_fragment.take_expression_fragment ();
   if (condition_expr->is_marked_for_strip ())
     rust_error_at (condition_expr->get_locus (),
 		   "cannot strip expression in this position - outer "
@@ -1692,6 +1698,9 @@ AttrVisitor::visit (AST::IfExprConseqIf &expr)
   // can't strip condition expr itself, but can strip sub-expressions
   auto &condition_expr = expr.get_condition_expr ();
   condition_expr->accept_vis (*this);
+  auto cond_fragment = expander.take_expanded_fragment (*this);
+  if (cond_fragment.should_expand ())
+    condition_expr = cond_fragment.take_expression_fragment ();
   if (condition_expr->is_marked_for_strip ())
     rust_error_at (condition_expr->get_locus (),
 		   "cannot strip expression in this position - outer "
@@ -1727,6 +1736,9 @@ AttrVisitor::visit (AST::IfExprConseqIfLet &expr)
   // can't strip condition expr itself, but can strip sub-expressions
   auto &condition_expr = expr.get_condition_expr ();
   condition_expr->accept_vis (*this);
+  auto cond_fragment = expander.take_expanded_fragment (*this);
+  if (cond_fragment.should_expand ())
+    condition_expr = cond_fragment.take_expression_fragment ();
   if (condition_expr->is_marked_for_strip ())
     rust_error_at (condition_expr->get_locus (),
 		   "cannot strip expression in this position - outer "

gcc/testsuite/rust/compile/macro42.rs

@@ -0,0 +1,31 @@
+// { dg-additional-options "-w -frust-cfg=A" }
+macro_rules! cfg {
+    () => {{}};
+}
+
+fn main() -> i32 {
+    let mut res = 0;
+    if cfg!(A) {
+        res = 1;
+    }
+
+    if cfg!(A) {
+        res = 2;
+    } else {
+        res = 3;
+    }
+
+    if cfg!(A) {
+        res = 4;
+    } else if cfg!(A) {
+        res = 5;
+    }
+
+    let res = if cfg!(A) {
+        6
+    } else {
+        7
+    };
+
+    return res;
+}