Merge pull request #22623 from c42f/propagate-sourceloc

provide `rewrite_sourceloc!` function

base/meta.jl

@@ -9,14 +9,16 @@ using ..CoreLogging
 
 export quot,
        isexpr,
+       replace_sourceloc!,
        show_sexpr,
        @dump
 
 """
     Meta.quot(ex)::Expr
 
-Quote expression `ex` to produce an expression with head `quote`. This can for instance be used to represent objects of type `Expr` in the AST.
-See also the manual section about [QuoteNode](@ref man-quote-node).
+Quote expression `ex` to produce an expression with head `quote`. This can for
+instance be used to represent objects of type `Expr` in the AST. See also the
+manual section about [QuoteNode](@ref man-quote-node).
 
 # Examples
 ```jldoctest
@@ -38,7 +40,10 @@ quot(ex) = Expr(:quote, ex)
 """
     Meta.isexpr(ex, head[, n])::Bool
 
-Check if `ex` is an expression with head `head` and `n` arguments.
+Return true if `ex` is an `Expr` with the given type `head` and optionally that
+the argument list is of length `n`. `head` may be a `Symbol` or collection of
+`Symbol`s. For example, to check that a macro was passed a function call
+expression, you might use `isexpr(ex, :call)`.
 
 # Examples
 ```jldoctest
@@ -66,6 +71,35 @@ isexpr(@nospecialize(ex), heads) = isa(ex, Expr) && in(ex.head, heads)
 isexpr(@nospecialize(ex), head::Symbol, n::Int) = isa(ex, Expr) && ex.head === head && length(ex.args) == n
 isexpr(@nospecialize(ex), heads, n::Int) = isa(ex, Expr) && in(ex.head, heads) && length(ex.args) == n
 
+"""
+    replace_sourceloc!(location, expr)
+
+Overwrite the caller source location for each macro call in `expr`, returning
+the resulting AST.  This is useful when you need to wrap a macro inside a
+macro, and want the inner macro to see the `__source__` location of the outer
+macro.  For example:
+
+```
+macro test_is_one(ex)
+    replace_sourceloc!(__source__, :(@test \$(esc(ex)) == 1))
+end
+@test_is_one 2
+```
+
+`@test` now reports the location of the call `@test_is_one 2` to the user,
+rather than line 2 where `@test` is used as an implementation detail.
+"""
+function replace_sourceloc!(sourceloc, @nospecialize(ex))
+    if ex isa Expr
+        if ex.head == :macrocall
+            ex.args[2] = sourceloc
+        end
+        map!(e -> replace_sourceloc!(sourceloc, e), ex.args, ex.args)
+    end
+    return ex
+end
+
+
 """
     Meta.show_sexpr([io::IO,], ex)
 

doc/src/base/base.md

@@ -388,6 +388,9 @@ Base.parentmodule
 Base.pathof(::Module)
 Base.moduleroot
 Base.@__MODULE__
+Base.@__FILE__
+Base.@__DIR__
+Base.@__LINE__
 Base.fullname
 Base.names
 Core.nfields

doc/src/base/file.md

@@ -48,9 +48,6 @@ Base.Filesystem.issticky
 Base.Filesystem.homedir
 Base.Filesystem.dirname
 Base.Filesystem.basename
-Base.@__FILE__
-Base.@__DIR__
-Base.@__LINE__
 Base.Filesystem.isabspath
 Base.Filesystem.isdirpath
 Base.Filesystem.joinpath

test/meta.jl

@@ -123,6 +123,16 @@ using Base.Meta
 @test isexpr(:(1+1),(:call,))
 @test isexpr(1,:call)==false
 @test isexpr(:(1+1),:call,3)
+
+let
+    fakeline = LineNumberNode(100000,"A")
+    # Interop with __LINE__
+    @test macroexpand(@__MODULE__, replace_sourceloc!(fakeline, :(@__LINE__))) == fakeline.line
+    # replace_sourceloc! should recurse:
+    @test replace_sourceloc!(fakeline, :((@a) + 1)).args[2].args[2] == fakeline
+    @test replace_sourceloc!(fakeline, :(@a @b)).args[3].args[2] == fakeline
+end
+
 ioB = IOBuffer()
 show_sexpr(ioB,:(1+1))