Fix incorrect source info in docstrings (#37048)

Fixes #36906, where source info wasn't being passed through
at-doc when it was applied to definitions defined within macros.

base/docs/Docs.jl

@@ -443,22 +443,22 @@ more than one expression is marked then the same docstring is applied to each ex
 """
 :(Core.@__doc__)
 
-function __doc__!(meta, def, define::Bool)
- @nospecialize meta def
+function __doc__!(source, mod, meta, def, define::Bool)
+ @nospecialize source mod meta def
  # Two cases must be handled here to avoid redefining all definitions contained in `def`:
  if define
  # `def` has not been defined yet (this is the common case, i.e. when not generating
  # the Base image). We just need to convert each `@__doc__` marker to an `@doc`.
  finddoc(def) do each
  each.head = :macrocall
- each.args = [Symbol("@doc"), nothing, meta, each.args[end], define] # TODO: forward line number info
+ each.args = [Symbol("@doc"), source, mod, nothing, meta, each.args[end], define]
  end
  else
  # `def` has already been defined during Base image gen so we just need to find and
  # document any subexpressions marked with `@__doc__`.
  docs = []
  found = finddoc(def) do each
- push!(docs, :(@doc($meta, $(each.args[end]), $define)))
+ push!(docs, :(@doc($source, $mod, $meta, $(each.args[end]), $define)))
  end
  # If any subexpressions have been documented then replace the entire expression with
  # just those documented subexpressions to avoid redefining any definitions.
@@ -509,6 +509,8 @@ function docm(source::LineNumberNode, mod::Module, ex)
  return REPL.lookup_doc(ex)
  end
 end
+# Drop incorrect line numbers produced by nested macro calls.
+docm(source::LineNumberNode, mod::Module, _, _, x...) = docm(source, mod, x...)
 
 # iscallexpr checks if an expression is a :call expression. The call expression may be
 # also part of a :where expression, so it unwraps the :where layers until it reaches the
@@ -578,7 +580,7 @@ function docm(source::LineNumberNode, mod::Module, meta, ex, define::Bool = true
  # Errors generated by calling `macroexpand` are passed back to the call site.
  isexpr(x, :error) ? esc(x) :
  # When documenting macro-generated code we look for embedded `@__doc__` calls.
- __doc__!(meta, x, define) ? esc(x) :
+ __doc__!(source, mod, meta, x, define) ? esc(x) :
  # Any "basic" expression such as a bare function or module name or numeric literal.
  isbasicdoc(x) ? objectdoc(source, mod, meta, nothing, x) :
 

test/docs.jl

@@ -433,6 +433,7 @@ macro example_1(f)
  end |> esc
 end
 
+const LINE_NUMBER_F = @__LINE__() + 1
 "f"
 @example_1 f
 
@@ -446,16 +447,23 @@ macro example_2(f)
  end |> esc
 end
 
+const LINE_NUMBER_G = @__LINE__() + 1
 "g"
 @example_2 g
 
 @example_2 _g
 
+const LINE_NUMBER_T = @__LINE__() + 1
+"T"
+Base.@kwdef struct T end
+
 end
 
 let md = meta(MacroGenerated)[@var(MacroGenerated.f)]
  @test md.order == [Tuple{Any}]
  @test docstrings_equal(md.docs[Tuple{Any}], doc"f")
+ @test md.docs[Tuple{Any}].data[:linenumber] == MacroGenerated.LINE_NUMBER_F
+ @test md.docs[Tuple{Any}].data[:path] == @__FILE__()
 end
 
 @test isdefined(MacroGenerated, :_f)
@@ -464,10 +472,19 @@ let md = meta(MacroGenerated)[@var(MacroGenerated.g)]
  @test md.order == [Tuple{Any}, Tuple{Any, Any}]
  @test docstrings_equal(md.docs[Tuple{Any}], doc"g")
  @test docstrings_equal(md.docs[Tuple{Any, Any}], doc"g")
+ @test md.docs[Tuple{Any}].data[:linenumber] == MacroGenerated.LINE_NUMBER_G
+ @test md.docs[Tuple{Any}].data[:path] == @__FILE__()
 end
 
 @test isdefined(MacroGenerated, :_g)
 
+let md = meta(MacroGenerated)[@var(MacroGenerated.T)]
+ @test md.order == Type[Union{}]
+ @test docstrings_equal(md.docs[Union{}], doc"T")
+ @test md.docs[Union{}].data[:linenumber] == MacroGenerated.LINE_NUMBER_T
+ @test md.docs[Union{}].data[:path] == @__FILE__()
+end
+
 module DocVars
 
 struct __FIELDS__ end