Leave a quoted callee that has no name alone in normalize_defsig

src/signatures.jl

@@ -253,9 +253,19 @@ end
 # try to normalize `def` to `GlobalRef` representation
 function normalize_defsig(@nospecialize(def), mod::Module)
     if def isa QuoteNode
-        # A quoted Symbol (e.g. the callee of `:foo(x)`) is already a name; only
-        # other wrapped values (functions, types, modules) need `nameof`.
-        def = def.value isa Symbol ? def.value : nameof(def.value)
+        val = def.value
+        if val isa Symbol
+            # A quoted Symbol (e.g. the callee of `:foo(x)`) is already a name.
+            def = val
+        elseif val isa Union{Function, DataType, UnionAll, Module}
+            # The quoted values that have a name (e.g. a `const` callee that
+            # JuliaInterpreter folded into a `QuoteNode`).
+            def = nameof(val)
+        else
+            # Any other quoted value, e.g. an instance of a callable struct that a macro
+            # interpolated as the callee of a call, is not a name: leave it as it is.
+            return def
+        end
     end
     if def isa Symbol
         def = GlobalRef(mod, def)

test/signatures.jl

@@ -626,6 +626,37 @@ end
     @test LoweredCodeUtils.identify_framemethod_calls(frame) isa Any  # must not throw
 end
 
+# A callable value that is neither a function, a type nor a module: it has no `nameof`.
+module QuotedCallee
+struct Offset
+    value::Float64
+end
+(offset::Offset)(x) = x + offset.value
+end
+
+@testset "normalize_defsig with a quoted callable value as callee" begin
+    # A macro may interpolate an arbitrary value as the callee of a call,
+    # `$(QuoteNode(Offset(2.0)))(x)`, which lowers to a `:call` whose callee is that
+    # `QuoteNode`. Only functions, types and modules have a `nameof`; any other quoted
+    # value is not a name and must be left as it is instead of throwing.
+    for val in (QuotedCallee.Offset(2.0), 1, "s", Union{Int,String})
+        qn = QuoteNode(val)
+        @test LoweredCodeUtils.normalize_defsig(qn, QuotedCallee) === qn
+    end
+    for (val, name) in ((sum, :sum), (Int, :Int64), (Base, :Base))
+        @test LoweredCodeUtils.normalize_defsig(QuoteNode(val), QuotedCallee) === GlobalRef(QuotedCallee, name)
+    end
+
+    ex = :(apply_offset(x) = $(QuoteNode(QuotedCallee.Offset(2.0)))(x))
+    methodinfos, selfcalls = LoweredCodeUtils.identify_framemethod_calls(Frame(QuotedCallee, ex))
+    @test haskey(methodinfos, GlobalRef(QuotedCallee, :apply_offset))
+    @test isempty(selfcalls)
+    signatures = MethodInfoKey[]
+    methoddefs!(signatures, Frame(QuotedCallee, ex))
+    @test length(signatures) == 1
+    @test Base.invokelatest(QuotedCallee.apply_offset, 3.0) == 5.0
+end
+
 module FoldedCallees
 struct Callable end
 end