treat _ as a wildcard, not a var, in function parameter in Move Lang …

…V2+ (#14962)

In Move Language 2.0+, treat a function parameter named "_" as a wildcard value-sink, not a variable.
Fixes #14949.

third_party/move/move-compiler-v2/src/env_pipeline/inliner.rs

@@ -45,6 +45,7 @@ use log::{debug, trace};
 use move_model::{
     ast::{Exp, ExpData, Operation, Pattern, Spec, SpecBlockTarget, TempIndex},
     exp_rewriter::ExpRewriterFunctions,
+    metadata::LanguageVersion,
     model::{FunId, GlobalEnv, Loc, NodeId, Parameter, QualifiedId},
     symbol::Symbol,
     ty::{ReferenceKind, Type},
@@ -833,7 +834,11 @@ impl<'env, 'rewriter> InlinedRewriter<'env, 'rewriter> {
             .map(|param| {
                 let Parameter(sym, ty, loc) = *param;
                 let id = env.new_node(loc.clone(), ty.instantiate(self.type_args));
-                if let Some(new_sym) = self.shadow_stack.get_shadow_symbol(*sym, true) {
+                if env.language_version().is_at_least(LanguageVersion::V2_0)
+                    && env.symbol_pool().string(*sym).as_ref() == "_"
+                {
+                    Pattern::Wildcard(id)
+                } else if let Some(new_sym) = self.shadow_stack.get_shadow_symbol(*sym, true) {
                     Pattern::Var(id, new_sym)
                 } else {
                     Pattern::Var(id, *sym)

third_party/move/move-compiler-v2/tests/checking-lang-v1/underscore.exp

@@ -0,0 +1,37 @@
+
+Diagnostics:
+error: undeclared `_`
+   ┌─ tests/checking-lang-v1/underscore.move:38:9
+   │
+38 │         _  // undefined
+   │         ^
+
+error: duplicate declaration of `_`
+   ┌─ tests/checking-lang-v1/underscore.move:41:30
+   │
+41 │     public fun test8(_: u64, _: u64): u64 {
+   │                      -       ^
+   │                      │
+   │                      previous declaration of `_`
+
+error: duplicate declaration of `_`
+   ┌─ tests/checking-lang-v1/underscore.move:46:37
+   │
+46 │     inline fun fun9(x: u64, _: u64, _: u64): u64 {
+   │                             -       ^
+   │                             │
+   │                             previous declaration of `_`
+
+error: duplicate declaration of `_`
+   ┌─ tests/checking-lang-v1/underscore.move:54:38
+   │
+54 │     inline fun fun10(x: u64, _: u64, _: |u64|u64): u64 {
+   │                              -       ^
+   │                              │
+   │                              previous declaration of `_`
+
+error: cannot pass `integer` to a function which expects argument of type `|u64|u64`
+   ┌─ tests/checking-lang-v1/underscore.move:59:21
+   │
+59 │         fun10(4, 3, 2)
+   │                     ^

third_party/move/move-compiler-v2/tests/checking-lang-v1/underscore.move

@@ -0,0 +1,101 @@
+//# publish
+module 0xc0ffee::m {
+    fun test2(): (u32, u64) {
+        (1u32, 2u64)
+    }
+
+    public fun test(_: u64): u64 {
+        let x = _ + 3;
+        x + _
+    }
+
+    public fun test3(_: u64): u64 {
+        let (_, _) = test2();
+        let x = _ + 3;
+        _ = _ + 1;
+        x + _
+    }
+
+    public fun test4(_: u64): u64 {
+        let (_, _x) = test2();
+        _ = _ + 2;
+        _
+    }
+
+    public fun test5(_: u64): u64 {
+        let (_, _) = test2();
+        _ = _ + 3;
+        _
+    }
+
+    public fun test6(_: u64): u64 {
+        let (_x, _) = test2();
+         _
+    }
+
+    public fun test7(_y: u64): u64 {
+        let _ = _y;
+        _  // undefined
+    }
+
+    public fun test8(_: u64, _: u64): u64 {
+        let _ = _;
+        _
+    }
+
+    inline fun fun9(x: u64, _: u64, _: u64): u64 {
+        x + 3
+    }
+
+    public fun test9(): u64 {
+        fun9(4, 3, 2)
+    }
+
+    inline fun fun10(x: u64, _: u64, _: |u64|u64): u64 {
+        x + 3
+    }
+
+    public fun test10a(): u64 {
+        fun10(4, 3, 2)
+    }
+
+    public fun test10b(): u64 {
+        fun10(4, 3, |x|x + 1)
+    }
+
+    public fun test10c(): u64 {
+        fun10(4, 3, |_|1)
+    }
+
+    inline fun fun11(x: u64, _: u64, f: |u64|u64): u64 {
+        f(x)
+    }
+
+    public fun test11(): u64 {
+        fun11(4, 3, |_|1)
+    }
+}
+
+//# run 0xc0ffee::m::test --args 4
+
+//# run 0xc0ffee::m::test3 --args 5
+
+//# run 0xc0ffee::m::test4 --args 5
+
+//# run 0xc0ffee::m::test5 --args 5
+
+//# run 0xc0ffee::m::test6 --args 5
+
+//# run 0xc0ffee::m::test7 --args 5
+
+//# run 0xc0ffee::m::test8 --args 5
+
+//# run 0xc0ffee::m::test9
+
+//# run 0xc0ffee::m::test10a
+
+//# run 0xc0ffee::m::test10b
+
+//# run 0xc0ffee::m::test10c
+
+//# run 0xc0ffee::m::test11

third_party/move/move-compiler-v2/tests/checking/naming/underscore.exp

@@ -0,0 +1,85 @@
+
+Diagnostics:
+error: undeclared `_`
+  ┌─ tests/checking/naming/underscore.move:8:17
+  │
+8 │         let x = _ + 3;
+  │                 ^
+
+error: undeclared `_`
+  ┌─ tests/checking/naming/underscore.move:9:13
+  │
+9 │         x + _
+  │             ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:14:17
+   │
+14 │         let x = _ + 3;
+   │                 ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:15:13
+   │
+15 │         _ = _ + 1;
+   │             ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:16:13
+   │
+16 │         x + _
+   │             ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:21:13
+   │
+21 │         _ = _ + 2;
+   │             ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:22:9
+   │
+22 │         _
+   │         ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:27:13
+   │
+27 │         _ = _ + 3;
+   │             ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:28:9
+   │
+28 │         _
+   │         ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:33:10
+   │
+33 │          _
+   │          ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:38:9
+   │
+38 │         _  // undefined
+   │         ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:42:17
+   │
+42 │         let _ = _;
+   │                 ^
+
+error: undeclared `_`
+   ┌─ tests/checking/naming/underscore.move:43:9
+   │
+43 │         _
+   │         ^
+
+error: cannot pass `integer` to a function which expects argument of type `|u64|u64`
+   ┌─ tests/checking/naming/underscore.move:59:21
+   │
+59 │         fun10(4, 3, 2)
+   │                     ^

third_party/move/move-compiler-v2/tests/checking/naming/underscore.move

@@ -0,0 +1,101 @@
+//# publish
+module 0xc0ffee::m {
+    fun test2(): (u32, u64) {
+        (1u32, 2u64)
+    }
+
+    public fun test(_: u64): u64 {
+        let x = _ + 3;
+        x + _
+    }
+
+    public fun test3(_: u64): u64 {
+        let (_, _) = test2();
+        let x = _ + 3;
+        _ = _ + 1;
+        x + _
+    }
+
+    public fun test4(_: u64): u64 {
+        let (_, _x) = test2();
+        _ = _ + 2;
+        _
+    }
+
+    public fun test5(_: u64): u64 {
+        let (_, _) = test2();
+        _ = _ + 3;
+        _
+    }
+
+    public fun test6(_: u64): u64 {
+        let (_x, _) = test2();
+         _
+    }
+
+    public fun test7(_y: u64): u64 {
+        let _ = _y;
+        _  // undefined
+    }
+
+    public fun test8(_: u64, _: u64): u64 {
+        let _ = _;
+        _
+    }
+
+    inline fun fun9(x: u64, _: u64, _: u64): u64 {
+        x + 3
+    }
+
+    public fun test9(): u64 {
+        fun9(4, 3, 2)
+    }
+
+    inline fun fun10(x: u64, _: u64, _: |u64|u64): u64 {
+        x + 3
+    }
+
+    public fun test10a(): u64 {
+        fun10(4, 3, 2)
+    }
+
+    public fun test10b(): u64 {
+        fun10(4, 3, |x|x + 1)
+    }
+
+    public fun test10c(): u64 {
+        fun10(4, 3, |_|1)
+    }
+
+    inline fun fun11(x: u64, _: u64, f: |u64|u64): u64 {
+        f(x)
+    }
+
+    public fun test11(): u64 {
+        fun11(4, 3, |_|1)
+    }
+}
+
+//# run 0xc0ffee::m::test --args 4
+
+//# run 0xc0ffee::m::test3 --args 5
+
+//# run 0xc0ffee::m::test4 --args 5
+
+//# run 0xc0ffee::m::test5 --args 5
+
+//# run 0xc0ffee::m::test6 --args 5
+
+//# run 0xc0ffee::m::test7 --args 5
+
+//# run 0xc0ffee::m::test8 --args 5
+
+//# run 0xc0ffee::m::test9
+
+//# run 0xc0ffee::m::test10a
+
+//# run 0xc0ffee::m::test10b
+
+//# run 0xc0ffee::m::test10c
+
+//# run 0xc0ffee::m::test11