Fix handling of discriminantless univariant enums in Rust; fix bug with encoded enums

2016-10-27  Manish Goregaokar  <manish@mozilla.com>

gdb/ChangeLog:
    * rust-lang.c (rust_get_disr_info): Treat univariant enums
    without discriminants as encoded enums with a real field
    * rust-lang.c (rust_evaluate_subexp): Handle field access
    on encoded struct-like enums

gdb/testsuite/ChangeLog:
    * simple.rs: Add test for univariant enums without discriminants
    and for encoded struct-like enums
    * simple.exp: Add test expectations

gdb/ChangeLog

@@ -1,3 +1,11 @@
+
+2016-10-27  Manish Goregaokar  <manish@mozilla.com>
+
+    * rust-lang.c (rust_get_disr_info): Treat univariant enums
+    without discriminants as encoded enums with a real field
+    * rust-lang.c (rust_evaluate_subexp): Handle field access
+    on encoded struct-like enums
+
 2016-11-03  Yao Qi  <yao.qi@linaro.org>
 
 	* Makefile.in (.y.c): Replace YY_NULL with YY_NULLPTR.

gdb/rust-lang.c

@@ -194,6 +194,18 @@ rust_get_disr_info (struct type *type, const gdb_byte *valaddr,
 	 has changed its debuginfo format.  */
       error (_("Could not find enum discriminant field"));
     }
+  else if (TYPE_NFIELDS (type) == 1)
+    {
+      /* Sometimes univariant enums are encoded without a
+         discriminant.  In that case, treating it as an encoded enum
+         with the first field being the actual type works.  */
+      const char *field_name = TYPE_NAME (TYPE_FIELD_TYPE (type, 0));
+      const char *last = rust_last_path_segment (field_name);
+      ret.name = concat (TYPE_NAME (type), "::", last, (char *) NULL);
+      ret.field_no = RUST_ENCODED_ENUM_REAL;
+      ret.is_encoded = 1;
+      return ret;
+    }
 
   if (strcmp (TYPE_FIELD_NAME (disr_type, 0), "RUST$ENUM$DISR") != 0)
     error (_("Rust debug format has changed"));
@@ -1725,7 +1737,9 @@ tuple structs, and tuple-like enum variants"));
 	    variant_type = TYPE_FIELD_TYPE (type, disr.field_no);
 
 	    if (variant_type == NULL
-		|| rust_tuple_variant_type_p (variant_type))
+	        || (disr.is_encoded
+	            ? rust_tuple_struct_type_p (variant_type)
+	            : rust_tuple_variant_type_p (variant_type)))
 	      error(_("Attempting to access named field %s of tuple variant %s, \
 which has only anonymous fields"),
 		    field_name, disr.name);

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2016-10-27  Manish Goregaokar  <manish@mozilla.com>
+
+    * gdb.rust/simple.rs: Add test for univariant enums without discriminants
+    and for encoded struct-like enums
+
 2016-10-28  Pedro Alves  <palves@redhat.com>
 
 	* gdb.base/maint.exp <maint info line-table w/o a file name>: Use

gdb/testsuite/gdb.rust/simple.exp

@@ -103,6 +103,11 @@ gdb_test_sequence "ptype z" "" {
 }
 gdb_test "print z.1" " = 8"
 
+gdb_test "print univariant" " = simple::Univariant::Foo{a: 1}"
+gdb_test "print univariant.a" " = 1"
+gdb_test "print univariant_anon" " = simple::UnivariantAnon::Foo\\(1\\)"
+gdb_test "print univariant_anon.0" " = 1"
+
 gdb_test_sequence "ptype simple::ByeBob" "" {
     " = struct simple::ByeBob \\("
     "  i32,"
@@ -220,3 +225,10 @@ gdb_test "print (1,)" "Tuple expressions not supported yet"
 gdb_test "print (1)" " = 1"
 
 gdb_test "print 23..97.0" "Range expression with different types"
+
+gdb_test "print (*parametrized.next.val)" \
+    " = simple::ParametrizedStruct<i32> {next: simple::ParametrizedEnum<Box<simple::ParametrizedStruct<i32>>>::Empty, value: 1}"
+gdb_test "print parametrized.next.val" \
+    " = \\(simple::ParametrizedStruct<i32> \\*\\) $hex"
+gdb_test "print parametrized" \
+    " = simple::ParametrizedStruct<i32> \\{next: simple::ParametrizedEnum<Box<simple::ParametrizedStruct<i32>>>::Val\\{val: $hex\\}, value: 0\\}"

gdb/testsuite/gdb.rust/simple.rs

@@ -63,6 +63,23 @@ enum SpaceSaver {
     Nothing,
 }
 
+enum Univariant {
+    Foo {a: u8}
+}
+enum UnivariantAnon {
+    Foo(u8)
+}
+
+enum ParametrizedEnum<T> {
+    Val { val: T },
+    Empty,
+}
+
+struct ParametrizedStruct<T> {
+    next: ParametrizedEnum<Box<ParametrizedStruct<T>>>,
+    value: T
+}
+
 fn main () {
     let a = ();
     let b : [i32; 0] = [];
@@ -93,6 +110,9 @@ fn main () {
     let y = HiBob {field1: 7, field2: 8};
     let z = ByeBob(7, 8);
 
+    let univariant = Univariant::Foo {a : 1};
+    let univariant_anon = UnivariantAnon::Foo(1);
+
     let slice = &w[2..3];
     let fromslice = slice[0];
     let slice2 = &slice[0..1];
@@ -117,6 +137,16 @@ fn main () {
     let custom_some = NonZeroOptimized::Value("hi".into());
     let custom_none = NonZeroOptimized::Empty;
 
+    let parametrized = ParametrizedStruct {
+        next: ParametrizedEnum::Val {
+            val: Box::new(ParametrizedStruct {
+                next: ParametrizedEnum::Empty,
+                value: 1,
+            })
+        },
+        value: 0,
+    };
+
     println!("{}, {}", x.0, x.1);        // set breakpoint here
     println!("{}", diff2(92, 45));
     empty();