fix: trigger error hints on exception supertypes too (#59843)

Fixes #58367

Co-authored-by: Dilum Aluthge <dilum@aluthge.com>
Co-authored-by: Jameson Nash <vtjnash@gmail.com>

Author: 3 people

base/experimental.jl

@@ -295,18 +295,18 @@ Closest candidates are:
     `if isdefined(Base.Experimental, :register_error_hint) ... end` block.
 """
 function register_error_hint(@nospecialize(handler), @nospecialize(exct::Type))
-    list = get!(Vector{Any}, _hint_handlers, exct)
-    push!(list, handler)
+    list = get!(Vector{Any}, _hint_handlers, Core.typename(exct))
+    push!(list, (exct, handler))
     return nothing
 end
 
-const _hint_handlers = IdDict{Type,Vector{Any}}()
+const _hint_handlers = IdDict{Core.TypeName,Vector{Any}}()
 
 """
     Experimental.show_error_hints(io, ex, args...)
 
 Invoke all handlers from [`Experimental.register_error_hint`](@ref) for the particular
-exception type `typeof(ex)`. `args` must contain any other arguments expected by
+exception type `typeof(ex)` and all of its supertypes. `args` must contain any other arguments expected by
 the handler for that type.
 
 !!! compat "Julia 1.5"
@@ -316,15 +316,20 @@ the handler for that type.
 """
 function show_error_hints(io, ex, args...)
     @nospecialize
-    hinters = get(_hint_handlers, typeof(ex), nothing)
-    isnothing(hinters) && return
-    for handler in hinters
-        try
-            @invokelatest handler(io, ex, args...)
-        catch
-            tn = typeof(handler).name
-            @error "Hint-handler $handler for $(typeof(ex)) in $(tn.module) caused an error" exception=current_exceptions()
+    ex_supertype = typeof(ex)
+    while ex_supertype != Any
+        hinters = get(_hint_handlers, Core.typename(ex_supertype), Any[])
+        for (exct, handler) in hinters
+            ex isa exct || continue
+            try
+                # TODO: deal with handlers accepting different signatures?
+                @invokelatest handler(io, ex, args...)
+            catch
+                tn = typeof(handler).name
+                @error "Hint-handler $handler for $(ex_supertype) in $(tn.module) caused an error" exception=current_exceptions()
+            end
         end
+        ex_supertype = supertype(ex_supertype)
     end
 end
 

test/errorshow.jl

@@ -740,7 +740,7 @@ let err_str
     @test occursin(Regex("MethodError: no method matching one\\(::.*HasNoOne; value::$(Int)\\)"), err_str)
     @test occursin("`one` doesn't take keyword arguments, that would be silly", err_str)
 end
-pop!(Base.Experimental._hint_handlers[MethodError])  # order is undefined, don't copy this
+pop!(Base.Experimental._hint_handlers[Core.typename(MethodError)])  # order is undefined, don't copy this
 
 function busted_hint(io, exc, notarg)  # wrong number of args
     print(io, "\nI don't have a hint for you, sorry")
@@ -752,7 +752,7 @@ catch ex
     io = IOBuffer()
     @test_logs (:error, "Hint-handler busted_hint for DomainError in $(@__MODULE__) caused an error") showerror(io, ex)
 end
-pop!(Base.Experimental._hint_handlers[DomainError])  # order is undefined, don't copy this
+pop!(Base.Experimental._hint_handlers[Core.typename(DomainError)])  # order is undefined, don't copy this
 
 struct ANumber <: Number end
 let err_str = @except_str ANumber()(3 + 4) MethodError
@@ -1476,3 +1476,38 @@ let err_str
     err_str = @except_str f56325(1,2) MethodError
     @test occursin("The anonymous function", err_str)
 end
+
+# Test that error hints catch abstract exception supertypes (issue #58367)
+
+module Hinterland
+
+abstract type AbstractHintableException <: Exception end
+struct ConcreteHintableException <: AbstractHintableException end
+gonnathrow() = throw(ConcreteHintableException())
+
+function Base.showerror(io::IO, exc::ConcreteHintableException)
+    print(io, "This is my exception")
+    Base.Experimental.show_error_hints(io, exc)
+end
+
+function __init__()
+    Base.Experimental.register_error_hint(ConcreteHintableException) do io, exc
+        print(io, "\nThis hint caught my concrete exception type")
+    end
+    Base.Experimental.register_error_hint(AbstractHintableException) do io, exc
+        print(io, "\nThis other hint caught my abstract exception supertype")
+    end
+end
+
+end
+
+@testset "Hints for abstract exception supertypes" begin
+    exc = try
+        Hinterland.gonnathrow()
+    catch e
+        e
+    end
+    exc_print = sprint(Base.showerror, exc)
+    @test occursin("This hint caught my concrete exception type", exc_print)
+    @test occursin("This other hint caught my abstract exception supertype", exc_print)
+end