Ensure type is monomorphic enough before evaluating size_of / align_of.

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -187,6 +187,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             }
             sym::size_of => {
                 let tp_ty = instance.args.type_at(0);
+                ensure_monomorphic_enough(tcx, tp_ty)?;
                 let layout = self.layout_of(tp_ty)?;
                 if !layout.is_sized() {
                     span_bug!(self.cur_span(), "unsized type for `size_of`");
@@ -196,6 +197,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             }
             sym::align_of => {
                 let tp_ty = instance.args.type_at(0);
+                ensure_monomorphic_enough(tcx, tp_ty)?;
                 let layout = self.layout_of(tp_ty)?;
                 if !layout.is_sized() {
                     span_bug!(self.cur_span(), "unsized type for `align_of`");

tests/ui/const-generics/generic_const_exprs/dependence_lint.full.stderr

@@ -16,15 +16,21 @@ LL |     let _: [u8; if true { size_of::<T>() } else { 3 }]; // error on stable,
    = note: type parameters may not be used in const expressions
    = help: add `#![feature(generic_const_exprs)]` to allow generic const expressions
 
-warning: cannot use constants which depend on generic parameters in types
+error: constant expression depends on a generic parameter
   --> $DIR/dependence_lint.rs:10:9
    |
 LL |     [0; size_of::<*mut T>()]; // lint on stable, error with `generic_const_exprs`
    |         ^^^^^^^^^^^^^^^^^^^
    |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
-   = note: `#[warn(const_evaluatable_unchecked)]` (part of `#[warn(future_incompatible)]`) on by default
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/dependence_lint.rs:10:5
+   |
+LL |     [0; size_of::<*mut T>()]; // lint on stable, error with `generic_const_exprs`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
 
 warning: cannot use constants which depend on generic parameters in types
   --> $DIR/dependence_lint.rs:18:9
@@ -34,6 +40,7 @@ LL |     [0; if false { size_of::<T>() } else { 3 }]; // lint on stable, error w
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
+   = note: `#[warn(const_evaluatable_unchecked)]` (part of `#[warn(future_incompatible)]`) on by default
 
-error: aborting due to 2 previous errors; 2 warnings emitted
+error: aborting due to 4 previous errors; 1 warning emitted
 

tests/ui/const-generics/generic_const_exprs/dependence_lint.rs

@@ -10,8 +10,8 @@ fn foo<T>() {
     [0; size_of::<*mut T>()]; // lint on stable, error with `generic_const_exprs`
     //[gce]~^ ERROR unconstrained
     //[gce]~| ERROR unconstrained generic constant
-    //[full]~^^^ WARNING cannot use constants
-    //[full]~| WARNING this was previously accepted
+    //[full]~^^^ ERROR constant expression depends on a generic parameter
+    //[full]~| ERROR constant expression depends on a generic parameter
     let _: [u8; size_of::<*mut T>()]; // error on stable, error with gce
     //[full]~^ ERROR generic parameters may not be used
     //[gce]~^^ ERROR unconstrained generic

tests/ui/const-generics/min_const_generics/complex-expression.rs

@@ -36,8 +36,8 @@ fn break_ty2<T>() {
 
 fn break_ty3<T>() {
     let _ = [0; size_of::<*mut T>() + 1];
-    //~^ WARN cannot use constants which depend on generic parameters in types
-    //~| WARN this was previously accepted by the compiler but is being phased out
+    //~^ ERROR constant expression depends on a generic parameter
+    //~| ERROR constant expression depends on a generic parameter
 }
 
 

tests/ui/const-generics/min_const_generics/complex-expression.stderr

@@ -61,15 +61,21 @@ LL |     let _: [u8; size_of::<*mut T>() + 1];
    = note: type parameters may not be used in const expressions
    = help: add `#![feature(generic_const_exprs)]` to allow generic const expressions
 
-warning: cannot use constants which depend on generic parameters in types
+error: constant expression depends on a generic parameter
   --> $DIR/complex-expression.rs:38:17
    |
 LL |     let _ = [0; size_of::<*mut T>() + 1];
    |                 ^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
-   = note: `#[warn(const_evaluatable_unchecked)]` (part of `#[warn(future_incompatible)]`) on by default
+   = note: this may fail depending on what value the parameter takes
 
-error: aborting due to 7 previous errors; 1 warning emitted
+error: constant expression depends on a generic parameter
+  --> $DIR/complex-expression.rs:38:13
+   |
+LL |     let _ = [0; size_of::<*mut T>() + 1];
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to 9 previous errors
 

tests/ui/const-generics/min_const_generics/const-evaluatable-unchecked.rs

@@ -1,11 +1,11 @@
-//@ check-pass
+//
 //@ compile-flags: -Zdeduplicate-diagnostics=yes
 #![allow(dead_code)]
 
 fn foo<T>() {
     [0; std::mem::size_of::<*mut T>()];
-    //~^ WARN cannot use constants which depend on generic parameters in types
-    //~| WARN this was previously accepted by the compiler but is being phased out
+    //~^ ERROR constant expression depends on a generic parameter
+    //~| ERROR constant expression depends on a generic parameter
 }
 
 struct Foo<T>(T);

tests/ui/const-generics/min_const_generics/const-evaluatable-unchecked.stderr

@@ -1,12 +1,18 @@
-warning: cannot use constants which depend on generic parameters in types
+error: constant expression depends on a generic parameter
   --> $DIR/const-evaluatable-unchecked.rs:6:9
    |
 LL |     [0; std::mem::size_of::<*mut T>()];
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
-   = note: `#[warn(const_evaluatable_unchecked)]` (part of `#[warn(future_incompatible)]`) on by default
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/const-evaluatable-unchecked.rs:6:5
+   |
+LL |     [0; std::mem::size_of::<*mut T>()];
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
 
 warning: cannot use constants which depend on generic parameters in types
   --> $DIR/const-evaluatable-unchecked.rs:17:21
@@ -16,6 +22,7 @@ LL |         let _ = [0; Self::ASSOC];
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
+   = note: `#[warn(const_evaluatable_unchecked)]` (part of `#[warn(future_incompatible)]`) on by default
 
 warning: cannot use constants which depend on generic parameters in types
   --> $DIR/const-evaluatable-unchecked.rs:29:21
@@ -26,5 +33,5 @@ LL |         let _ = [0; Self::ASSOC];
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
 
-warning: 3 warnings emitted
+error: aborting due to 2 previous errors; 2 warnings emitted
 

tests/ui/consts/size-align-monomorphic.rs

@@ -0,0 +1,21 @@
+// Regression test for #149081. Check that an attempt to evaluate size_of / align_of intrinsics
+// during an optimization, when type parameter is not monomorphic enough, doesn't lead to a
+// compilation failure.
+//
+//@compile-flags: --crate-type=lib -O
+//@build-pass
+
+pub fn size_align_of<T: WithAssoc<Assoc = U>, U>() -> (usize, usize) {
+    let a = const { std::mem::size_of::<Wrapper<T>>() };
+    let b = const { std::mem::align_of::<Wrapper<T>>() };
+    (a, b)
+}
+
+pub struct Wrapper<T: WithAssoc> {
+    pub assoc2: <T::Assoc as WithAssoc>::Assoc,
+    pub value: T,
+}
+
+pub trait WithAssoc {
+    type Assoc: WithAssoc;
+}