Support aggregate expressions

tests/mir-opt/building/custom/aggregate_exprs.adt.built.after.mir

@@ -0,0 +1,16 @@
+// MIR for `adt` after built
+
+fn adt() -> Onion {
+    let mut _0: Onion;                   // return place in scope 0 at $DIR/aggregate_exprs.rs:+0:13: +0:18
+    let mut _1: i32;                     // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+    let mut _2: Foo;                     // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+    let mut _3: Bar;                     // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+
+    bb0: {
+        _1 = const 1_i32;                // scope 0 at $DIR/aggregate_exprs.rs:+6:13: +6:20
+        _2 = Foo { a: const 1_i32, b: const 2_i32 }; // scope 0 at $DIR/aggregate_exprs.rs:+7:13: +10:14
+        _3 = Bar::Foo(move _2, _1);      // scope 0 at $DIR/aggregate_exprs.rs:+11:13: +11:39
+        _0 = Onion { neon: ((_3 as variant#0).1: i32) }; // scope 0 at $DIR/aggregate_exprs.rs:+12:13: +12:58
+        return;                          // scope 0 at $DIR/aggregate_exprs.rs:+13:13: +13:21
+    }
+}

tests/mir-opt/building/custom/aggregate_exprs.array.built.after.mir

@@ -0,0 +1,15 @@
+// MIR for `array` after built
+
+fn array() -> [i32; 2] {
+    let mut _0: [i32; 2];                // return place in scope 0 at $DIR/aggregate_exprs.rs:+0:15: +0:23
+    let mut _1: [i32; 2];                // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+    let mut _2: i32;                     // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+
+    bb0: {
+        _1 = [const 42_i32, const 43_i32]; // scope 0 at $DIR/aggregate_exprs.rs:+5:13: +5:25
+        _2 = const 1_i32;                // scope 0 at $DIR/aggregate_exprs.rs:+6:13: +6:20
+        _1 = [_2, const 2_i32];          // scope 0 at $DIR/aggregate_exprs.rs:+7:13: +7:25
+        _0 = move _1;                    // scope 0 at $DIR/aggregate_exprs.rs:+8:13: +8:26
+        return;                          // scope 0 at $DIR/aggregate_exprs.rs:+9:13: +9:21
+    }
+}

tests/mir-opt/building/custom/aggregate_exprs.rs

@@ -0,0 +1,71 @@
+#![feature(custom_mir, core_intrinsics)]
+
+extern crate core;
+use core::intrinsics::mir::*;
+
+// EMIT_MIR aggregate_exprs.tuple.built.after.mir
+#[custom_mir(dialect = "built")]
+fn tuple() -> (i32, bool) {
+    mir!(
+        {
+            RET = (1, true);
+            Return()
+        }
+    )
+}
+
+// EMIT_MIR aggregate_exprs.array.built.after.mir
+#[custom_mir(dialect = "built")]
+fn array() -> [i32; 2] {
+    mir!(
+        let x: [i32; 2];
+        let one: i32;
+        {
+            x = [42, 43];
+            one = 1;
+            x = [one, 2];
+            RET = Move(x);
+            Return()
+        }
+    )
+}
+
+struct Foo {
+    a: i32,
+    b: i32,
+}
+
+enum Bar {
+    Foo(Foo, i32),
+}
+
+union Onion {
+    neon: i32,
+    noun: f32,
+}
+
+// EMIT_MIR aggregate_exprs.adt.built.after.mir
+#[custom_mir(dialect = "built")]
+fn adt() -> Onion {
+    mir!(
+        let one: i32;
+        let x: Foo;
+        let y: Bar;
+        {
+            one = 1;
+            x = Foo {
+                a: 1,
+                b: 2,
+            };
+            y = Bar::Foo(Move(x), one);
+            RET = Onion { neon: Field(Variant(y, 0), 1) };
+            Return()
+        }
+    )
+}
+
+fn main() {
+    assert_eq!(tuple(), (1, true));
+    assert_eq!(array(), [1, 2]);
+    assert_eq!(unsafe { adt().neon }, 1);
+}

tests/mir-opt/building/custom/aggregate_exprs.tuple.built.after.mir

@@ -0,0 +1,10 @@
+// MIR for `tuple` after built
+
+fn tuple() -> (i32, bool) {
+    let mut _0: (i32, bool);             // return place in scope 0 at $DIR/aggregate_exprs.rs:+0:15: +0:26
+
+    bb0: {
+        _0 = (const 1_i32, const true);  // scope 0 at $DIR/aggregate_exprs.rs:+3:13: +3:28
+        return;                          // scope 0 at $DIR/aggregate_exprs.rs:+4:13: +4:21
+    }
+}