Fix missing bounds checks for trailing zero dimensions (#23723)

This fixes issue #23629 for 0.6. It is done independently from the fix for master (in #23628) due to all the deprecation changes.

base/abstractarray.jl

@@ -407,9 +407,10 @@ function checkbounds_indices(::Type{Bool}, IA::Tuple, I::Tuple{Any})
 end
 function checkbounds_linear_indices(::Type{Bool}, IA::Tuple{Vararg{OneTo}}, i)
     @_inline_meta
-    if checkindex(Bool, IA[1], i)
+    ts = trailingsize(IA)
+    if checkindex(Bool, IA[1], i) && ts > 0
         return true
-    elseif checkindex(Bool, OneTo(trailingsize(IA)), i)  # partial linear indexing
+    elseif checkindex(Bool, OneTo(ts), i)  # partial linear indexing
         partial_linear_indexing_warning_lookup(length(IA))
         return true # TODO: Return false after the above function is removed in deprecated.jl
     end

src/cgutils.cpp

@@ -1726,17 +1726,24 @@ static Value *emit_array_nd_index(const jl_cgval_t &ainfo, jl_value_t *ex, ssize
             // the accessed array, i.e. `if !(i < alen) goto error`.
             if (nidxs > 1) {
                 // TODO: REMOVE DEPWARN AND RETURN FALSE AFTER 0.6.
-                // We need to check if this is inside the non-linearized size
+                // We need to check if this index is inside its non-linearized dimension
                 BasicBlock *partidx = BasicBlock::Create(jl_LLVMContext, "partlinidx");
                 BasicBlock *partidxwarn = BasicBlock::Create(jl_LLVMContext, "partlinidxwarn");
+                BasicBlock *trailingcheck = BasicBlock::Create(jl_LLVMContext, "trailingcheck");
                 Value *d = emit_arraysize_for_unsafe_dim(ainfo, ex, nidxs, nd, ctx);
-                builder.CreateCondBr(builder.CreateICmpULT(ii, d), endBB, partidx);
+                Value *alen = emit_arraylen(ainfo, ex, ctx);
+                builder.CreateCondBr(builder.CreateICmpULT(ii, d), trailingcheck, partidx);
+
+                // If it is inside its own dimension, we still need to ensure all other
+                // dimensions are non-zero
+                ctx->f->getBasicBlockList().push_back(trailingcheck);
+                builder.SetInsertPoint(trailingcheck);
+                builder.CreateCondBr(builder.CreateICmpULT(ii, alen), endBB, failBB);
 
                 // We failed the normal bounds check; check to see if we're
                 // inside the linearized size (partial linear indexing):
                 ctx->f->getBasicBlockList().push_back(partidx);
                 builder.SetInsertPoint(partidx);
-                Value *alen = emit_arraylen(ainfo, ex, ctx);
                 builder.CreateCondBr(builder.CreateICmpULT(i, alen), partidxwarn, failBB);
 
                 // We passed the linearized bounds check; now throw the depwarn:

test/arrayops.jl

@@ -2119,3 +2119,8 @@ Base.:(==)(a::T11053, b::T11053) = a.a == b.a
 
 #15907
 @test typeof(Array{Int,0}()) == Array{Int,0}
+
+@testset "issue 23629" begin
+    @test_throws BoundsError zeros(2,3,0)[2,3]
+    @test_throws BoundsError checkbounds(zeros(2,3,0), 2, 3)
+end