RFC: Add reasons

src/JET.jl

@@ -619,6 +619,7 @@ const JULIA_DIR = @static occursin("DEV", string(VERSION)) ?
 
 # default UI (console)
 include("ui/print.jl")
+include("ui/reasons.jl")
 
 # entries
 # =======

src/abstractinterpret/inferenceerrorreport.jl

@@ -230,7 +230,7 @@ _get_sig_type(::StateAtPC, @nospecialize(x)) = Any[repr(x; context = :compact =>
 """
     InferenceErrorReport
 
-An interface type of error reports that JET collects by abstract interpration.
+An interface type of error reports that JET collects by abstract interpretation.
 If `T` implements this interface, the following requirements should be satisfied:
 
 ---

src/ui/reasons.jl

@@ -0,0 +1,39 @@
+"""
+    JET.reasons(results)
+
+Construct a unique set of "reasons" for errors. Each reason is a unique file/line location, signature, and explanation.
+
+`results` is most easily constructed from SnoopCompile's `report.(itrigs)`, where `itrigs` is a list of inference triggers.
+See the SnoopCompile documentation for details.
+"""
+reasons(results::AbstractVector{<:JETCallResult}) = unique(reduce(vcat, filter(!isempty, reasons.(results)); init=Reason[]))
+reasons(result::JETCallResult) = Reason.(get_reports(result))
+
+struct Reason
+    report::InferenceErrorReport
+end
+
+# A limited form of comparison so as to aggregate equivalent errors that were
+# arrived at by different callgraphs
+function Base.:(==)(a::Reason, b::Reason)
+    a.report.msg == b.report.msg || return false
+    af, bf = a.report.vst[end], b.report.vst[end]
+    af.file == bf.file && af.line == bf.line || return false
+    a.report.sig == b.report.sig
+end
+
+const reason_seed = Int === Int64 ? 0xfbdf9de4cc04c870 : 0x5e6fcd4e
+function Base.hash(r::Reason, h::UInt)
+    h = hash(reason_seed, h)
+    h = hash(r.report.msg, h)
+    f = r.report.vst[end]
+    h = hash(f.file, h)
+    h = hash(f.line)
+    h = hash(r.report.sig, h)
+end
+
+function Base.show(io::IO, r::Reason)
+    print_error_report(io, r.report)
+    f = r.report.vst[end]
+    print(io, f.file, ':', f.line)
+end